WO2009029539A1

WO2009029539A1 - Mixtures and catalyst systems including transition metal-containing catalysts and noble metal-containing catalysts, processes for their preparation, and processes for their use in oxidation reactions

Info

Publication number: WO2009029539A1
Application number: PCT/US2008/074088
Authority: WO
Inventors: Fuchen Liu; Juan Arhancet; Erik Sall; Henry Chien
Original assignee: Monsanto Technology Llc
Priority date: 2007-08-24
Filing date: 2008-08-22
Publication date: 2009-03-05

Abstract

This invention relates to the field of heterogeneous catalysis, and more particularly to catalyst mixtures comprising catalysts that include one or more transition metals in combination with nitrogen formed on or over the surface of a carbon support, and a catalyst comprising a noble metal at a surface of a carbon support. The invention also relates to the field of catalytic oxidation reactions, including the preparation of secondary amine by the catalytic oxidation of tertiary amines utilizing the catalysts and mixtures detailed herein.

Description

MIXTURES AND CATALYST SYSTEMS INCLUDING TRANSITION METAL-CONTAINING CATALYSTS AND NOBLE METAL-CONTAINING CATALYSTS, PROCESSES FOR THEIR PREPARATION, AND PROCESSES FOR THEIR USE IN OXIDATION REACTIONS

FIELD OF INVENTION

[0001] This invention relates to the field of heterogeneous catalysis, and more particularly to catalyst mixtures comprising catalysts that include one or more transition metals in combination with nitrogen and/or carbon formed on or over the surface of a carbon support, and a catalyst comprising a noble metal at a surface of a carbon support. The invention also relates to the field of catalytic oxidation reactions, including the preparation of secondary amines by the catalytic oxidation of tertiary amines utilizing the catalysts and mixtures detailed herein .

BACKGROUND OF INVENTION

[0002] N- (phosphonomethyl) glycine (known in the agricultural chemical industry as glyphosate) is described in Franz, U.S. Patent No. 3,799,758. Glyphosate and its salts are conveniently applied as a post-emergent herbicide in an aqueous formulation. It is a highly effective and commercially important broad-spectrum herbicide useful in killing or controlling the growth of a wide variety of plants, including germinating seeds, emerging seedlings, maturing and established woody and herbaceous vegetation, and aquatic plants.

[0003] Various methods for producing glyphosate are known in the art, including various methods utilizing carbon-supported noble metal-containing catalysts. See, for example, U.S. Patent No. 6,417,133 to Ebner et al. and Wan et al . International Publication No. WO 2006/031938. Generally, these methods include the liquid phase oxidative cleavage of N- (phosphonomethyl) iminodiacetic acid (i.e., PMIDA) in the presence of a carbon-supported noble metal-containing catalyst. Along with glyphosate product, various by-products may form, such as formaldehyde, formic acid (which is formed by the oxidation of the formaldehyde by-product) ; aminomethylphosphonic acid (AMPA) and methyl aminomethylphosphonic acid (MAMPA) , which are formed by the oxidation of glyphosate; and iminodiacetic acid (IDA) , which is formed by the de-phosphonomethylation of PMIDA. These by-products may reduce glyphosate yield (e.g., AMPA and/or MAMPA) and may introduce toxicity issues (e.g., formaldehyde) . Thus, significant by-product formation is preferably avoided.

[0004] It is generally known in the art including, for example, as described in Ebner et al. U.S. 6,417,133 and Wan et al. WO 2006/031938, that carbon primarily catalyzes the oxidation of PMIDA to glyphosate and the noble metal primarily catalyzes the oxidation of by-product formaldehyde to carbon dioxide, and water. The catalysts of Ebner et al . U.S. 6,417,133 and Wan et al . WO 2006/031938 have proven to be highly advantageous and effective catalysts for the oxidation of PMIDA to glyphosate and the oxidation of by-products formaldehyde and formic acid to carbon dioxide and water without excessive leaching of noble metal from the carbon support. These catalysts are also effective in the operation of a continuous process for the production of glyphosate by oxidation of PMIDA. Even though these catalysts are effective in PMIDA oxidation and are generally resistant to noble metal leaching under PMIDA oxidation conditions, there exist opportunities for improvement. For example, one drawback to these catalysts is the presence of costly noble metal.

[0005] Transition metal-containing catalysts for the oxidation of PMIDA to glyphosate are described in Liu et al . International Publication No. WO 2005/016519 and Arhancet et al . International Publication No. WO 2006/089193. These catalysts have demonstrated effectiveness for the oxidation of PMIDA to glyphosate and the oxidation of by-products formaldehyde and formic acid to carbon dioxide and water. In fact, these catalysts may demonstrate greater activity for PMIDA oxidation than noble metal-containing catalysts under certain conditions. Advantageously, these catalysts do not require the presence of a costly noble metal. However, with regard to by-product oxidation, these catalysts may be less effective than noble metal-containing catalysts.

[0006] Accordingly, it would be advantageous to have a multi-reaction catalytic material and reaction process that oxidizes PMIDA to glyphosate while simultaneously exhibiting desired oxidation of formaldehyde and formic acid (e.g., activity comparable to currently-utilized noble metal-containing catalysts) , and which requires a reduced noble metal content as compared to catalysts currently available for commercial manufacture of glyphosate. For example, it would be advantageous to have a multi-reaction catalytic material and reaction process more effective for PMIDA and/or by-product oxidation, generally or on a per unit catalytic metal weight basis, than conventional noble metal-containing catalysts.

SUMMARY OF THE INVENTION

[0007] This invention provides catalysts, mixtures, and catalyst systems useful in various heterogeneous oxidation reactions, including the preparation of secondary amines by the catalytic oxidation of tertiary amines. For example, the present invention is directed to catalyst mixtures that comprise catalysts that include supports, particularly carbon supports, and which have compositions comprising one or more transition metals in combination with nitrogen and/or carbon formed on or over the surface of a carbon support. These catalysts may optionally include a secondary metallic element in combination with nitrogen and/or carbon formed on or over the surface of the carbon support. Generally, the catalyst mixtures of the present invention also include a catalyst including a noble metal at a surface of a carbon support.

[0008] The catalytic materials of the present invention disclosed herein are particularly useful in the oxidative cleavage of PMIDA reagents such as N- (phosphonomethyl) iminodiacetic acid to form an N- (phosphonomethyl) glycine product. In such reactions, the combination of a transition metal-containing catalyst and a noble metal-containing catalyst have proven to be active for the oxidation of the PMIDA substrate, and effective in catalysis of the oxidation of formaldehyde and formic acid by-products. In particular, mixtures of the present invention have been discovered to function effectively for oxidation of PMIDA to glyphosate and simultaneous oxidation of formaldehyde and formic acid, but with reduced noble metal requirements as compared to noble metal-containing catalysts currently available for commercial manufacture of glyphosate.

[0009] Briefly, therefore, the present invention is directed to mixtures comprising a transition metal catalyst and a noble metal catalyst. The transition metal catalyst comprises a transition metal composition on a carbon support; the transition metal composition comprises a transition metal and nitrogen. The noble metal catalyst comprises a noble metal at a surface of a carbon support.

[0010] In one embodiment, the transition metal constitutes greater than 1% by weight of the transition metal catalyst.

[0011] In another embodiment, the transition metal catalyst comprises an activated carbon support and the transition metal constitutes at least 1.6% by weight of the catalyst.

[0012] In a still further embodiment, the carbon support of the transition metal catalyst has a Langmuir surface area of from about 500 m²/g to about 2100 m²/g, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst .

[0013] In another embodiment, the transition metal (M) catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ when the catalyst is analyzed by Time-of- Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A. The weighted molar average value of x is from about 0.5 to 2.0, the weighted molar average value of y is from about 0.5 to about 8.0, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

[0014] In a still further embodiment, the transition metal (M) catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ when the catalyst is analyzed by Time-of- Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A. The transition metal constitutes greater than 2% by weight of the transition metal catalyst, the weighted molar average value of x is from about 0.5 to about 8, and the weighted molar average value of y is from about 0.5 to about 8. In another such embodiment, the weighted molar average value of x is from about 0.5 to 2.2.

[0015] In another embodiment, the transition metal (M) is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; and the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ when the transition metal catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A, wherein the relative abundance of ions in which x is 1 is at least 42%.

[0016] In a further embodiment, the micropore Langmuir surface area of the transition metal catalyst is at least about 70% of the micropore Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon, and the transition metal constitutes at least 1.6% by weight of the catalyst.

[0017] In one embodiment, the transition metal constitutes at least about 2% by weight of the transition metal catalyst, and the micropore Langmuir surface area of the transition metal catalyst is from about 60% to less than 80% of the micropore Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon.

[0018] In a further embodiment, the transition metal constitutes from about 2% to less than 5% by weight of the transition metal catalyst, and the micropore Langmuir surface area of the transition metal catalyst is at least about 60% of the micropore Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon.

[0019] In a still further embodiment, the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the transition metal constitutes at least about 2% by weight of the transition metal catalyst; and the total Langmuir surface area of the transition metal catalyst is at least about 60% of the total Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon .

[0020] In another embodiment, the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the total Langmuir surface area of the transition metal catalyst is less than about 2000 m²/g; the total Langmuir surface area of the transition metal catalyst is at least about 75% of the total Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon; and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

[0021] In a still further embodiment, the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the transition metal constitutes at least about 2% by weight of the transition metal catalyst; the total Langmuir surface area of the transition metal catalyst is less than about 2000 m²/g; and the total Langmuir surface area of the transition metal catalyst is at least about 60% of the total Langmuir surface area of the carbon support of the transition metal catalyst prior to formation of the transition metal composition thereon.

[0022] The present invention is further directed to catalyst systems comprising a liquid medium having a transition metal catalyst, a noble metal catalyst, and a supplemental promoter dispersed therein. In one embodiment, the transition metal catalyst comprises a transition metal composition on a carbon support and the noble metal catalyst comprises a noble metal at a surface of a carbon support. The transition metal composition comprises a transition metal and nitrogen.

[0023] The present invention is further directed to processes for the oxidation of an organic substrate, the processes comprising contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of a transition metal catalyst and a noble metal catalyst. For example, the present invention is directed to processes for the oxidation of an organic substrate utilizing a mixture or system as set forth above.

[0024] The present invention is also directed to a process for the oxidation of an organic substrate, the process comprising contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of a supplemental promoter, a transition metal catalyst, and a noble metal catalyst. The transition metal catalyst comprises a transition metal composition on a carbon support; the transition metal composition comprises a transition metal and nitrogen. The noble metal catalyst comprises a noble metal at a surface of a carbon support.

[0025] The present invention is further directed to a process for the oxidation of an organic substrate, the process comprising contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of bismuth, tellurium, a transition metal catalyst, and a noble metal catalyst. The transition metal catalyst comprises a transition metal composition on a carbon support; the transition metal composition comprises a transition metal and nitrogen. The noble metal catalyst comprises a noble metal at a surface of a carbon support.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Fig. 1 is a High Resolution Transmission Electron Microscopy (HRTEM) image of a carbon-supported molybdenum carbide .

[0027] Fig. 2 is a SEM image of a carbon supported molybdenum carbide.

[0028] Fig. 3 is a TEM image of a carbon supported molybdenum carbide.

[0029] Fig. 4 shows the percentage of carbon dioxide in the exit gas produced during N- (phosphonomethyl) iminodiacetic acid (PMIDA) oxidation carried out using various catalysts as described in Example 2. [0030] Fig. 5 shows carbon dioxide profiles of PMIDA oxidation carried out using various catalysts as described in Example 2.

[0031] Fig. 6 shows carbon dioxide profiles of PMIDA oxidation carried out using various catalysts as described in Example 4.

[0032] Figs. 7-10 show the carbon dioxide percentage in the exit gas produced during PMIDA oxidation as described in Example 5.

[0033] Fig. 11 shows the results of the carbon dioxide drop-point measurement comparison as described in Example 8.

[0034] Fig. 12 shows carbon dioxide generation during PMIDA oxidation carried out as described in Example 20. Figs. 13-14 show a comparison of the pore surface area of various catalysts as described in Example 15.

[0035] Figs. 15-26 show X-ray diffraction (XRD) results for catalyst samples analyzed as described in Example 17.

[0036] Figs. 27-37 are SEM images of catalyst samples analyzed as described in Example 18.

[0037] Fig. 38 is an Energy dispersive X-ray analysis spectroscopy (EDS) spectrum of a catalyst sample analyzed as described in Example 18.

[0038] Figs. 39 and 40 are TEM images of catalyst samples analyzed as described in Example 18.

[0039] Figs. 41 and 42 are SEM Images of catalyst samples analyzed as described in Example 18.

[0040] Figs. 43 and 44 are TEM images of catalyst samples analyzed as described in Example 18.

[0041] Figs. 45-48 are SEM Images of catalyst samples analyzed as described in Example 18.

[0042] Figs. 49 and 50 are TEM images of catalyst samples analyzed as described in Example 18. [0043] Figs. 51 and 52 are X-ray Photoelectron Spectroscopy (XPS) results for samples analyzed as described in Example 19.

[0044] Fig. 53 is a Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) for a 1.5% cobalt carbide-nitride (CoCN) catalyst analyzed as described in Example 24.

[0045] Figs. 54, 55, 56 and 57 show the intensities of ion species detected during ToF SIMS analysis of a 1.1% iron tetraphenyl porphyrin (FeTPP), a 1.0% iron carbide-nitride (FeCN), a 1.5% cobalt tetramethoxy phenylporphyrin (CoTMPP) catalyst, and a 1.0% cobalt carbide-nitride (CoCN) catalyst, respectively, as described in Example 24.

[0046] Figs. 58, 59 and 60 show the intensities of ion species detected during ToF SIMS analysis of 1.5%, 5% and 10% cobalt carbide-nitride (CoCN) catalysts, respectively, as described in Example 24.

[0047] Fig. 61 shows the intensities of ion species detected during ToF SIMS analysis of a 1.0% cobalt phthalocyanine (CoPLCN) catalyst as described in Example 24.

[0048] Figs. 62A, 62B, 63A and 63B are TEM images for a 1% cobalt phthalocyanine (CoPLCN) catalyst analyzed as described in Example 25.

[0049] Figs. 64A and 64B are TEM images for a 1.5% cobalt tetramethoxy phenylporphyrin (CoTMPP) catalyst analyzed as described in Example 25.

[0050] Figs. 65A and 65B are TEM images for a 1.5% cobalt tetramethoxy phenylporphyrin (CoTMPP) catalyst analyzed as described in Example 25.

[0051] Figs. 66 and 67 show PMIDA oxidation results described in Example 26.

[0052] Figs. 68 and 69 show PMIDA oxidation results described in Example 27.

[0053] Fig. 70 shows pore volume distributions for catalysts analyzed as described in Example 29. [0054] Figs. 71A-87B are SEM and TEM images of catalysts analyzed as described in Example 31.

[0055] Figs. 88A-93 show Small Angle X-Ray Scattering (SAXS) results for catalysts analyzed as described in Example 32.

[0056] Figs. 94-104 are X-Ray Photoelectron Spectroscopy spectra for catalysts analyzed as described in Example 33.

[0057] Figs. 105-108 shows Time-of-Flight Secondary Ion Mass Spectroscopy (ToF SIMS) results for various catalysts analyzed as described in Example 34.

[0058] Figs. 109A and 109B show spectra obtained by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Example 35.

[0059] Figs. 110-112 show PMIDA reaction testing results as described in Example 61. Figs. 113A and 113B show microscopy results described in Example 39.

[0060] Figs. 114A and 114B show microscopy results described in Example 40.

[0061] Fig. 115 shows PMIDA reaction testing results as described in Example 43.

[0062] Fig. 116 shows PMIDA reaction testing results as described in Example 68. Figs. 117-124 show PMIDA reaction testing results as described in Example 45.

[0063] Figs. 125-131 show PMIDA reaction testing results as described in Example 46.

[0064] Figs. 132-138 show PMIDA reaction testing results as described in Example 47.

[0065] Figs. 139-145 show PMIDA reaction testing results as described in Example 48.

[0066] Figs. 146-150 show PMIDA reaction testing results as described in Example 49.

[0067] Figs. 151-157 show PMIDA reaction testing results as described in Example 50. [0068] Figs. 158-164 show PMIDA reaction testing results as described in Example 51.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] Described herein are mixtures that comprise a transition metal-containing catalyst and a noble metal- containing catalyst. As described below, including the Examples, transition metal-containing catalysts prepared as detailed herein and exhibiting one or more of the properties detailed herein are effective for PMIDA oxidation and the oxidation of formaldehyde and formic acid by-products of PMIDA oxidation. Noble metal-containing catalysts (e.g., those described in U.S. Patent No. 6,417,133 to Ebner et al . and Wan et al. International Publication No. WO 2006/031938) are also effective for these purposes, and have proven their utility in the commercial manufacture of glyphosate. Where the transition metal catalyst comprises a transition metal that is not a platinum group metal, it will in many instances offer significant economies as compared to a noble metal catalyst in processes for oxidation of organic substrates.

[0070] Based on the experimental results provided herein, the transition metal-containing catalysts may provide enhanced activity for PMIDA oxidation as compared to noble metal- containing catalysts utilized in mixtures detailed herein, while such noble metal-containing catalysts may provide enhanced oxidation of formaldehyde and/or formic acid by-products of PMIDA oxidation as compared to transition metal-containing catalysts. In accordance with various embodiments of the present invention, the mixture comprises a transition metal- containing catalyst and a noble metal-containing catalyst to capitalize on these advantageous properties of each catalyst. In particular, it is currently believed that the transition metal catalyst provides at least a portion of the mixture's activity for the oxidation of PMIDA. Since the transition metal-containing catalyst may provide enhanced activity for PMIDA oxidation as compared to a noble metal-containing catalyst, this portion of the mixture may provide performance and/or economic benefits as compared to the use of noble metal- containing catalysts alone in the manufacture of glyphosate. Similarly, improved oxidation of formaldehyde and formic acid by-products of noble metal-containing catalysts as compared to transition metal-containing catalysts provides a performance benefit that generally justifies the expense associated with the noble metal, especially in the oxidation of a tertiary amine such as PMIDA to a secondary amine such as glyphosate. Use of a mixture that essentially represents replacement of a portion of such a noble metal-containing catalyst with a transition metal- containing catalyst effective for PMIDA oxidation that does not require a costly noble metal provides a significant economic benefit over utilizing the noble metal-containing catalyst alone. Since the transition metal-containing catalyst is equally or nearly as effective for PMIDA oxidation as the noble metal-containing catalyst, the economic benefit is achieved without an unacceptable loss, if any, of effectiveness for PMIDA oxidation .

[0071] A mixture of the present invention may represent an advance in the art without necessarily providing improved PMIDA and/or by-product oxidation as compared to noble metal- containing catalysts typically used in the commercial manufacture of glyphosate. That is, to the extent that the PMIDA and/or by-product oxidation performance of the mixture approaches or equals the performance of a noble metal-containing catalyst, the mixture may provide improved oxidation on a per unit catalyst cost basis as compared to the noble metal catalyst regardless of any absolute improvement in PMIDA and/or byproduct oxidation. In fact, PMIDA and by-product oxidation performances at least equal to those achieved by noble metal- containing catalysts have been achieved using mixtures of the present invention. In particular, mixtures have been observed to provide performances substantially equal to noble metal catalysts that have demonstrated utility in commercial manufacture of glyphosate and provide a benchmark for measuring the performance of these mixtures and other catalysts. As noted, transition metal catalysts detailed herein may exhibit greater activity for PMIDA oxidation as compared to noble metal catalysts, while noble metal catalysts may exhibit greater activity for oxidation of by-products of PMIDA oxidation. It has been discovered that the performances achieved using the mixtures of the present invention do not simply represent a weighted average of PMIDA and by-product oxidation performances but, rather, mixture performances have been shown to be very near or equal to the performances observed with noble metal catalysts alone. In particular, it has been observed that the mixture can provide by-product (e.g., formaldehyde and/or formic acid) oxidation near or equal to that of noble metal catalysts. This result was not expected. It is believed that one skilled in the art would have expected the mixture to provide activities that more closely represent a combination, or average, of the demonstrated activities of each individual catalyst. As noted, achieving performances equivalent to a noble metal catalyst represent a significant economic benefit.

[0072] The performance of the mixture catalyst as described herein may, in fact, provide improved selectivity for PMIDA, formaldehyde, and/or formic acid oxidation as compared to conventional noble metal-containing catalysts, representing a further advance in the art.

[0073] It is to be further understood that utilizing a mixture including a transition metal-containing and noble metal- containing catalyst is not meant to diminish the advantages associated with either type of catalyst. As noted, noble metal- containing catalysts have demonstrated stability for PMIDA oxidation and activity for oxidation of formaldehyde and formic acid by-products in the commercial manufacture of glyphosate that have outweighed the cost issue associated with its noble metal requirements. Moreover, transition metal-containing catalysts, as shown in the Examples below, have demonstrated activity for oxidation of PMIDA and formaldehyde and formic acid by-products without the requirement of a costly noble metal. In fact, transition metal-containing catalysts described herein have proven to be effective multi-reaction catalysts in the absence of any noble metal-containing catalyst as described, for example, in Liu et al . International Publication No. WO 2005/016519 and Arhancet et al . International Publication No. WO 2006/089193.

[0074] The present invention is further directed to mixtures (or catalyst systems) that include a supplemental promoter along with a transition metal-containing catalyst and a noble metal-containing catalyst.

[0075] Utility of a supplemental promoter (e.g., bismuth, tellurium, or a compound containing either bismuth or tellurium) in combination with a noble metal-containing catalyst has been demonstrated as described, for example, in U.S. Patent Nos. 6,586,621 and 6,963,009, and International Publication No. WO 01/46208, the entire disclosures of which are incorporated herein by reference for all relevant purposes. Use of a supplemental promoter in combination with a noble metal catalyst in PMIDA oxidation has been found to enhance the capability of the noble metal catalyst for catalyzing the oxidation of PMIDA, and the formaldehyde and formic acid by-products. It has also been found that use of a supplemental promoter in some instances (e.g., when bismuth is utilized) may also reduce the portion of the noble metal that is leached from the carbon support. [0076] It is currently believed that the presence of the supplemental promoter may promote the conversion of PMIDA, formaldehyde, and/or formic acid by altering the noble metal catalyst properties as conversion reaches a transition point. This transition point may typically be represented, or accompanied by a reduction in the rate of oxygen flow. During operation beyond the transition point, the presence of the promoter favors the kinetics of the formaldehyde and/or formic acid (i.e., Ci) oxidation relative to the kinetics of the PMIDA oxidation, or of the further oxidation of glyphosate to aminomethylphosphonic acid (AMPA) . This does not necessarily represent an acceleration in Ci oxidation, but the rate of Ci oxidation is enhanced relative to PMIDA and/or glyphosate oxidation at the noble metal catalyst surface so that Ci oxidation is achieved without excessive formation of N-methyl-N- (phosphonomethyl) glycine (NMG) or AMPA. Although this effect might be visualized as providing more time for the Ci oxidation, it is believed that the more basic effect is that the kinetics of Ci oxidation are favored relative to the kinetics of PMIDA or glyphosate oxidation. The supplemental promoter is also believed to retard oxygen poisoning of the noble metal catalyst on which the Ci oxidation primarily proceeds.

[0077] Control of by-products without excessive AMPA or NMG formation is also promoted by management of oxygen flows. Because of the high activity of the transition metal catalyst for the PMIDA oxidation, there is a high oxygen demand during most of the PMIDA conversion and advantage can be taken of this in achieving high productivity. To further control overoxidation, the oxygen flow may be substantially reduced after a drop in residual PMIDA concentration in the reaction medium (e.g., to about 2 wt.%) . The latter concentration may also approximately represent the above-mentioned transition point at which the presence of the promoter favors the kinetics of Ci oxidation relative to the kinetics of PMIDA or glyphosate oxidation. Under the conditions prevailing at this point in the reaction, the reduced oxygen supply limits the oxidation of glyphosate to AMPA without a comparable limitation on the continuing oxidation of CiS. In this regard it is to be noted that management of oxygen flows may be used to provide desired effects in connection with use of a mixture including a transition metal catalyst and a noble metal catalyst either with or without a supplemental promoter.

[0078] Also described herein are catalyst combinations including a primary catalyst comprising a primary transition metal combined with a secondary catalyst comprising a secondary metallic element (e.g., titanium) . In various embodiments, the primary catalyst comprises a primary transition metal composition formed on or over the surface of a carbon support. The secondary catalyst (i.e., co-catalyst), may include a catalytic composition comprising a secondary metallic element and formed on or over the surface of a carbon support. The secondary catalyst may also comprise a microporous crystalline material having a transition metal incorporated into its lattice including, for example, titanium-containing zeolites. Catalyst combinations including a transition metal catalyst may be incorporated into mixtures along with a noble metal catalyst in the same manner as a transition metal catalyst alone.

[0079] Reference to a "transition metal catalyst" or "noble metal catalyst" herein does not does not eliminate the possibility of catalytic activity provided by portions of these catalysts other than a metal-containing active phase (e.g., a carbon support having a transition metal composition and/or noble metal at a surface thereof) . It is to be understood that transition metal catalyst as described herein extends to active phases comprising any transition metal and nitrogen, any transition metal other than platinum and nitrogen, any transition metal other than platinum and palladium, and any transition metal other than platinum group metals and nitrogen.

I . Transition Metal Catalysts

[0080] Transition metal catalysts of the invention comprise at least one transition metal composition. In various embodiments, the catalysts comprise a primary transition metal composition, a secondary metallic element and a carbon support. The primary transition metal composition comprises a primary transition metal composition and nitrogen. The secondary metallic element can be incorporated as part of the primary transition metal composition; or it may form or be comprised by a secondary catalytic composition, which may optionally be formed on a separate support. The catalyst is understood to have sites that are active for the oxidation of a first substrate and sites that are active for the second substrate, which may be the same as or different from the first substrate.

[0081] In various embodiments the transition metal catalyst comprises a primary transition metal composition comprising one or more primary transition metals and the catalyst further comprises an additional (i.e., secondary) metallic element. The secondary metallic element may be incorporated into the composition comprising the primary transition metal or metals or the catalyst may comprise a secondary catalytic composition comprising the secondary metallic element on or over the surface of the carbon support and/or the primary transition metal composition .

[0082] Transition metal catalysts of the present invention generally comprise one or more active phases, which are effective for catalyzing the oxidation of a substrate. In various embodiments, the catalyst comprises an active phase comprising a transition metal composition comprising one or more transition metals, nitrogen and/or carbon. Advantageously, in various such embodiments, such an active phase is effective for catalyzing the oxidation of both a first substrate and a second substrate. For example, in the preparation of glyphosate from PMIDA, the first substrate may typically comprise PMIDA and the second substrate may comprise formaldehyde or formic acid, which are by-products of the PMIDA oxidation. In these and other embodiments, the catalyst may comprise an active phase comprising a transition metal composition comprising both a primary transition metal and a secondary metallic element, and such active phase is effective for catalyzing the oxidation of both a first substrate and an additional substrate different from the first substrate. In various other embodiments, the catalyst comprises a first active phase comprising a primary transition metal composition and a second active phase comprising a secondary catalytic composition. The first active phase is generally formed on or over the surface of the carbon support while the second active phase is formed on or over the surface of the carbon support and/or formed on or over the surface of the first active phase or primary transition metal composition. Additionally or alternatively, a first active comprising a primary transition metal composition may be formed on or over the surface of a second active phase comprising a secondary catalytic composition. Advantageously, in various such embodiments, the first active phase is effective for catalyzing the oxidation of a first substrate (e.g., PMIDA) and the second active phase is effective for catalyzing the oxidation of a substrate which may the same as or different from the first substrate (e.g., formaldehyde or formic acid byproducts of PMIDA oxidation) . In the case of catalysts comprising a primary transition metal composition and a secondary metallic element, typically activity for the catalytic oxidation of the first substrate is imparted predominantly by the primary transition metal composition. As described in detail herein, the primary transition metal composition may also comprise carbon, and typically comprises a carbide, nitride or carbide-nitride of the primary transition metal. Activity for the oxidation of the second substrate is imparted predominantly by the presence of the secondary metallic element and/or by a secondary catalytic composition comprising a compound or complex of the secondary metallic element on or over a common carbon support, or optionally formed on a separate support, which may be carbon, silica, alumina or zeolite. Such compound or complex may, for example, comprise a carbide, nitride, carbide-nitride, or oxide of the secondary metallic element.

[0083] Regardless of the presence of a secondary metallic element or secondary catalytic composition comprised thereby, active sites effective for the oxidation of the first substrate are believed to catalyze either two electron or four electron reduction of oxygen. Two electron reduction of oxygen results in the formation of hydrogen peroxide or other peroxides which can potentially react to cause oxidation of the first or second substrate, but the active sites effective for the oxidation of the first substrate by four electron transfer may not always be effective for catalyzing the oxidation of the second substrate. In particular, they may not be effective to catalyze oxidation by reaction of the substrate with a peroxide compound. However, active sites afforded by a secondary metallic element are believed to catalyze oxidation of the second substrate by reaction with hydrogen peroxide or other peroxide compound. Experimental results have indicated that oxidation of second substrates such as formaldehyde is promoted by the secondary metallic element, and that such oxidation may comprise reaction with hydrogen peroxide. Thus, the combination of the first active sites and other active sites provide benefits in enhanced oxidation of the two substrates, and more particularly the second substrate. [0084] In certain embodiments of the invention, both the primary transition metal composition and the secondary metallic element may be present in a single active phase which presents sites active for contact with and oxidation of both types of substrates. In other embodiments, the primary transition metal composition may be contained in one active phase which presents the sites active for oxidation of the first substrate, and the secondary metallic element or secondary catalytic composition may be present in a second active phase which presents sites active for oxidation of the second substrate. Where the catalyst comprises separate active phases, the first active phase may be deposited on the carbon support and the second active phase may be formed on the support or on the first active phase, or over both. Alternatively, the second active phase may be deposited on the support and the first active phase formed on the support or on the second active phase or over both.

[0085] As further discussed herein the catalyst may comprise a combination of a first catalyst comprising the first active phase and a second catalyst comprising the second active phase. In these embodiments, the first active phase may comprise noble metal active sites provided by a noble metal on carbon catalyst of the type described by U.S. Patent No. 6,417,133 to Ebner et al . ; or alternatively, the first active phase may be comprised by the surface of an active carbon that has been treated in the manner described in U.S. Patent Nos . 4,624,937 and 4,696,772 to Chou .

[0086] Transition metal and catalytic compositions formed on or over the surface of a carbon support in accordance with the catalysts and catalyst combinations of the present invention generally comprise a transition metal or metallic element and nitrogen (e.g., a transition metal nitride); a transition metal or metallic element and carbon (e.g., a transition metal carbide) ; or a transition metal or metallic element, nitrogen, and carbon (e.g., a transition metal carbide-nitride) .

[0087] Transition metal catalysts (and catalyst combinations and mixtures comprised thereby) of the present invention may be used to catalyze liquid phase (e.g., in an aqueous solution or an organic solvent) oxidation reactions and, in particular, the oxidation of a tertiary amine (e.g., N- (phosphonomethyl) iminodiacetic acid) to produce a secondary amine (e.g., N- (phosphonomethyl) glycine) . Advantageously, the transition metal catalysts and transition metal catalyst- containing mixtures and combinations of the present invention also catalyze oxidation of the formaldehyde and/or formic acid by-products that are formed in the oxidation of N- (phosphonomethyl) iminodiacetic acid to

N- (phosphonomethyl) glycine . It has been observed that catalysts of the present invention comprising a transition metal composition comprising one or more transition metals, nitrogen and/or carbon formed on or over the surface of a carbon support comprise an active phase effective to catalyze the oxidation of N- (phosphonomethyl) iminodiacetic acid to

N- (phosphonomethyl) glycine and the oxidation of formaldehyde and/or formic acid byproducts. In addition, various transition metal catalysts of the present invention include a first active phase and/or a primary transition metal composition as described herein that is effective to catalyze the oxidation of N- (phosphonomethyl) iminodiacetic acid to

N- (phosphonomethyl) glycine and a second active phase and/or secondary catalytic composition effective to catalyze the oxidation of formaldehyde and/or formic acid byproducts. Similarly, various catalyst combinations of the present invention include a primary catalyst effective to catalyze the oxidation of N- (phosphonomethyl) iminodiacetic acid to N- (phosphonomethyl) glycine and a secondary catalyst effective to catalyze the oxidation of formaldehyde and/or formic acid byproducts .

[0088] Reference to the catalytic activity of a particular active phase (e.g., first active phase) for oxidation of a particular substrate should not be taken as exclusive of catalytic activity for oxidation of another substrate. For example, a secondary metallic element, secondary catalytic composition or secondary catalyst may exhibit catalytic activity for the oxidation of N- (phosphonomethyl) iminodiacetic acid to N- (phosphonomethyl) glycine . In addition, reference to the catalytic activity of an active phase or transition metal composition or catalytic composition formed on a carbon support or primary or secondary catalyst incorporating such a composition should not be taken as exclusive of the catalytic activity of the carbon support itself. For example, the carbon support alone is known to catalyze the oxidation of tertiary amines to secondary amines.

[0089] By evaluating experimental data for a particular substrate and process, applying standard economic principles, those skilled in the art can weigh the advantages of using a single catalyst comprising a primary transition metal and a secondary metallic element or using a catalyst combination including a primary transition metal and a secondary metallic element .

[0090] Further described herein are processes for preparing transition metal compositions and catalytic compositions comprising a transition metal or metallic element and nitrogen; a transition metal or metallic element and carbon; or a transition metal or metallic element, nitrogen, and carbon on or over the surface of a carbon support. A. Supporting Structure

[0091] Generally, the supporting structure may comprise any material suitable for formation of a transition metal composition or catalytic composition thereon. Preferably, the supporting structure is in the form of a carbon support.

[0092] In general, the carbon supports used in the present invention are well known in the art. Activated, non-graphitized carbon supports are preferred. These supports are characterized by high adsorptive capacity for gases, vapors, and colloidal solids and relatively high specific surface areas. The support suitably may be a carbon, char, or charcoal produced by means known in the art, for example, by destructive distillation of wood, peat, lignite, coal, nut shells, bones, vegetable, or other natural or synthetic carbonaceous matter, but preferably is "activated" to develop adsorptive power. Activation usually is achieved by heating to high temperatures (800-900⁰C) with steam or with carbon dioxide which brings about a porous particle structure and increased specific surface area. In some cases, hygroscopic substances, such as zinc chloride and/or phosphoric acid or sodium sulfate, are added before the destructive distillation or activation, to increase adsorptive capacity. Preferably, the carbon content of the carbon support ranges from about 10% for bone charcoal to about 98% for some wood chars and nearly 100% for activated carbons derived from organic polymers. The non-carbonaceous matter in commercially available activated carbon materials normally will vary depending on such factors as precursor origin, processing, and activation method. Many commercially available carbon supports contain small amounts of metals. In certain embodiments, carbon supports having the fewest oxygen-containing functional groups at their surfaces are most preferred.

[0093] The form of the carbon support is not critical. In certain embodiments, the support is a monolithic support. Suitable monolithic supports may have a wide variety of shapes. Such a support may be, for example, in the form of a screen or honeycomb. Such a support may also, for example, be in the form of a reactor impeller.

[0094] In a particularly preferred embodiment, the support is in the form of particulates. Because particulate supports are especially preferred, most of the following discussion focuses on embodiments which use a particulate support. It should be recognized, however, that this invention is not limited to the use of particulate supports.

[0095] Suitable particulate supports may have a wide variety of shapes. For example, such supports may be in the form of granules. Even more preferably, the support is in the form of a powder. These particulate supports may be used in a reactor system as free particles, or, alternatively, may be bound to a structure in the reactor system, such as a screen or an impeller.

[0096] Typically, a support which is in particulate form comprises a broad size distribution of particles. For powders, preferably at least about 95% of the particles are from about 2 to about 300 μm in their largest dimension, more preferably at least about 98% of the particles are from about 2 to about 200 μm in their largest dimension, and most preferably about 99% of the particles are from about 2 to about 150 μm in their largest dimension with about 95% of the particles being from about 3 to about 100 μm in their largest dimension. Particles being greater than about 200 μm in their largest dimension tend to fracture into super-fine particles (i.e., less than 2 μm in their largest dimension), which are difficult to recover.

[0097] In the following discussion, specific surface areas of carbon supports and the transition metal catalysts of the present invention are provided in terms of the well-known Langmuir method using N₂. However, such values generally correspond to those measured by the also well-known Brunauer- Emmett-Teller (B. E. T.) method using N₂.

[0098] The specific surface area of the carbon support, typically measured by the Langmuir method using N₂, is preferably from about 10 to about 3,000 m²/g (surface area of carbon support per gram of carbon support) , more preferably from about 500 to about 2,100 m²/g, and still more preferably from about 750 to about 2,100 m²/g. In some embodiments, the most preferred specific area is from about 750 to about 1,750 m²/g. In other embodiments, typically the particulate carbon support has a Langmuir surface area of at least about 1000 m²/g prior to formation of a transition metal composition on the carbon support, more typically at least about 1200 m²/g and, still more typically, at least about 1400 m²/g. Preferably, the Langmuir surface area of the carbon support prior to formation of a transition metal composition on the carbon support is from about 1000 to about 1600 m²/g and, more preferably, from about 1000 to about 1500 m²/g prior to formation of a transition metal composition on the carbon support.

[0099] The Langmuir micropore surface area of the support (i.e., surface area of the support attributed to pores having a diameter less than 20 A) is typically at least about 300 m²/g, more typically at least about 600 m²/g. Preferably, the Langmuir micropore surface area is from about 300 to about 1500 m²/g and, more preferably, from about 600 to about 1400 m²/g. The Langmuir combined mesopore and macropore surface area of the support (i.e., surface area of the support attributed to pores having a diameter greater than 20 A) is typically at least about 100 m²/g, more typically at least about 150 m²/g. Preferably, the combined Langmuir mesopore and macropore surface area is from about 100 to about 400 m²/g, more preferably from about 100 to about 300 m²/g and, still more preferably, from about 150 to about 250 m²/g. [00100] For certain applications (e.g., hydrogenation, petroleum hydrotreating, and isomerization) , non-carbon supports may be used with a catalyst containing a transition metal composition or catalytic composition formed on the support as described herein. For example, silica and alumina supports having Langmuir surface areas of at least about 50 m²/g. Typically, these supports will have Langmuir surface areas of from about 50 to about 300 m²/g. Such supports are also effective for use in oxidation catalysts as described herein.

[00101] Generally, supports having high surface areas are preferred because they tend to produce a finished catalyst having a high surface area.

[00102] Finished transition metal catalysts exhibiting sufficient pore volume are desired so that reactants are able to penetrate the pores of the finished catalyst. The pore volume of the support may vary widely. Generally, the pore volume of the support is at least about 0.1 cm³/g (pore volume per gram of support) and, typically, at least about 0.5 cm³/g. Typically, the pore volume is from about 0.1 to about 2.5 cm³/g and, more typically, from about 1.0 to about 2.0 cm³/g. Preferably, the pore volume of the support is from about 0.2 to about 2.0 cm³/g, more preferably from about 0.4 to about 1.7 cm³/g and, still more preferably, from about 0.5 to about 1.7 cm³/g. Catalysts comprising supports with pore volumes greater than about 2.5 cm³/g tend to fracture easily. On the other hand, catalysts comprising supports having pore volumes less than 0.1 cm³/g tend to have small surface areas and therefore low activity.

[00103] Penetration of reactants into the pores of the finished catalysts is also affected by the pore size distribution of the support. Typically, at least about 60% of the pore volume of the support is made up of pores having a diameter of at least about 20 A. Preferably, from about 60 to about 75% of the pore volume of the support is made up of pores having a diameter of at least about 20 A.

[00104] Typically, at least about 20% of the pore volume of the support is made up of pores having a diameter of between about 20 and about 40 A. Preferably, from about 20 to about 35% of the pore volume of the support is made of pores having a diameter of between about 20 and about 40 A. Typically, at least about 25% of the pore volume of the support is made up of pores having a diameter of at least about 40 A. Preferably, from about 25 to about 60% of the pore volume of the support is made up of pores having a diameter of at least about 40 A. Typically, at least about 5% of the pore volume of the support is made up of pores having a diameter of between about 40 and about 60 A. Preferably, from about 5 to about 20% of the pore volume of the support is made up of pores having a diameter of between about 40 and about 60 A.

[00105] Carbon supports for use in the present invention are commercially available from a number of sources. The following is a listing of some of the activated carbons which may be used with this invention: Darco G-60 Spec and Darco X (ICI-America, Wilmington, Del.); Norit SG Extra, Norit EN4, Norit EXW, Norit A, Norit Ultra-C, Norit ACX, and Norit 4x14 mesh (Amer. Norit Co., Inc., Jacksonville, FIa.); Gl-9615, VG-8408, VG-8590, NB- 9377, XZ, NW, and JV (Barnebey-Cheney, Columbus, Ohio) ; BL PuIv., PWA PuIv., Calgon C 450, and PCB Fines (Pittsburgh Activated Carbon, Div. of Calgon Corporation, Pittsburgh, Pa.); P-100 (No. Amer. Carbon, Inc., Columbus, Ohio); Nuchar CN, Nuchar C-1000 N, Nuchar C-190 A, Nuchar C-115 A, and Nuchar SA- 30 (Westvaco Corp., Carbon Department, Covington, Va.); Code 1551 (Baker and Adamson, Division of Allied Amer. Norit Co., Inc., Jacksonville, FIa.); Grade 235, Grade 337, Grade 517, and Grade 256 (Witco Chemical Corp., Activated Carbon Div., New York, N. Y.); and Columbia SXAC (Union Carbide New York, N. Y.). B . Transition Metal Compositions and Catalytic

Compositions

[00106] Transition metal compositions (e.g., primary transition metal compositions) formed on or over the surface of a carbon support generally comprise a transition metal and nitrogen; a transition metal and carbon; or a transition metal, nitrogen, and carbon. Similarly, catalytic compositions (e.g., secondary catalytic compositions) formed on or over the surface of a carbon support and/or formed on or over the surface of a primary transition metal composition generally comprise a metallic element (e.g., a secondary metallic element which may be denoted as M(II)) and nitrogen; a metallic element and carbon; or a metallic element, nitrogen, and carbon.

[00107] In various embodiments, transition metal catalysts of the present invention comprise a transition metal composition at a surface of a carbon support. The transition metal compositions typically comprise a transition metal (e.g., a primary transition metal) selected from the group consisting of Group IB, Group VB, Group VIB, Group VIIB, iron, cobalt, nickel, lanthanide series metals, and combinations thereof. Groups of elements as referred to herein are with reference to the Chemical Abstracts Registry (CAS) system for numbering the elements of the Periodic Table (e.g., Group VIII includes iron, cobalt, and nickel) . In particular, the primary transition metal is typically selected from the group consisting of copper (Cu) , silver (Ag) , vanadium (V) , chromium (Cr) , molybdenum (Mo) , tungsten (W) , manganese (Mn) , iron (Fe) , cobalt (Co) , nickel (Ni), cerium (Ce), and combinations thereof. In certain embodiments, the primary transition metal is typically selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof. In various preferred embodiments the transition metal is cobalt. In certain other embodiments, the primary transition metal composition includes a plurality of primary transition metals (e.g., cobalt and cerium) .

[00108] In various embodiments, transition metal catalysts of the present invention further comprise a secondary catalytic composition comprising a secondary metallic element which can be formed on or over the surface of a carbon support and/or formed on or over the surface of a primary transition metal composition formed on the carbon support. Additionally or alternatively, the secondary metallic element can be incorporated into a transition metal composition further comprising a primary transition metal. The secondary metallic element is typically selected from the group consisting of Group HB, Group IVB, Group VB, Group VIB, Group VIIB, Group HA, Group VIA, nickel, copper, and combinations thereof. Thus, the secondary metallic element is typically selected from the group consisting of zinc (Zn) , titanium (Ti) , vanadium, molybdenum, manganese, barium (Ba) , calcium (Ca) , magnesium (Mg) , tellurium (Te) , selenium (Se), nickel, copper, and combinations thereof. Although selenium and tellurium are generally classified as non-metals, they exist in allotropic forms that are lustrous and sometimes referred to as "metallic," and can function as semiconductors. They are, thus, referred to herein as "metallic elements," though not as "metals." In various preferred embodiments, the secondary metallic element is a transition metal (i.e., secondary transition metal) selected from the group consisting of zinc, titanium, vanadium, molybdenum, manganese, barium, magnesium, nickel, copper, and combinations thereof. Thus, in these embodiments, the secondary catalytic composition may properly be referred to as a secondary transition metal composition .

[00109] It is recognized that, depending on the context, any of several different transition metals may qualify as either a primary transition metal or a secondary metallic element. Thus, where two or more of such transition metals are present, they may in some instances function as plural primary transition metals and in other instances one or more of them may function as secondary metallic elements. The criteria for classification in this regard include the nature of the composition (s) in which each metal is present, and the relative effectiveness of the metals and the compositions within which they are included for oxidation of different substrates. More particularly, it will be understood that, to qualify as a primary transition metal, the metal must be comprised by a composition that also contains nitrogen. Otherwise the metal can qualify only as a secondary metallic element. It will be further understood that, where a composition comprising a given transition metal and nitrogen, for example, a nitride or carbide-nitride thereof, is less effective on a unit gram-atom metal basis than a composition or active phase comprising another transition metal and nitrogen for oxidation of a first substrate but more effective than the composition comprising the another metal for oxidation of a second substrate that is formed as a by-product of the oxidation of the first substrate, the another metal qualifies as a primary transition metal and the given metal qualifies as a secondary metallic element. For example, a primary transition metal composition is effective for catalyzing the oxidation of a first substrate (e.g., N- (phosphonomethyl) iminodiacetic acid) while a secondary metallic element or secondary catalytic composition comprising such element is less effective than the primary transition metal for oxidation of

N- (phosphonomethyl) iminodiacetic acid. However, in various preferred embodiments, the secondary metallic element or second catalytic composition is more effective than (or enhances the effectiveness of) the primary transition metal composition for catalyzing the oxidation of formaldehyde and/or formic acid byproducts formed in the oxidation of N-

(phosphonomethyl) iminodiacetic acid catalyzed by a primary transition metal.

[00110] Without being held to a particular theory, it is believed that the secondary metallic element or secondary catalytic composition may enhance the effectiveness of the catalyst as a whole for catalyzing the oxidation of the second substrate by reaction with hydrogen peroxide formed in the reduction of oxygen as catalyzed by either the primary transition metal composition, the secondary metallic element or the secondary catalytic composition. Aside from other criteria, any transition metal which has such enhancing effect may be considered a secondary metallic element for purposes of the present invention.

[00111] It is recognized that the same element may qualify as a primary transition metal with regard to one process and the first and second substrates oxidized therein, but qualify as a secondary metallic element for another combination of first and second substrates . But the functional definitions set out above may be applied for classification of a given metal in a given context. It will, in any event, be understood that the present invention contemplates bi-metallic catalysts including both combinations of plural primary transition metals and combinations of primary transition metal compositions and secondary metallic elements. Elements which may function as either primary transition metals or secondary metallic elements include, for example, copper, nickel, vanadium, manganese, or molybdenum. Specific combinations which may constitute plural primary transition metals in one context and a combination of primary transition metal and secondary metallic element in another include Co/Cu, Co/Ni, Co/V, Co/Mn, Co/Mo, Fe/Cu, Fe/Ni, Fe/V, Fe/Mn, Fe/Mo, Mo/Cu, Mo/Ni, Mo/V, Mo/Mn, Mo/Mo, W/Cu, W/Ni, W/V, W/Mn, W/Mo, Cu/Cu, Cu/Ni, Cu/V, Cu/Mn, Cu/Mo, Ag/Cu, Ag/Ni, Ag/V, Ag/Mn, Ag/Mo, V/Cu, V/Ni, V/V, V/Mn, V/Mo, Cr/Cu, Cr/Ni, Cr/V, Cr/Mn, Cr/Mo, Mn/Cu, Mn/Ni, Mn/V, Mn/Mn, Mn/Mo, Ni/Cu, Ni/Ni, Ni/V, Ni/Mn, Ni/Mo, Ce/Cu, Ce/Ni, Ce/V, Ce/Mn, and Ce/Mo.

[00112] Generally, transition metal compositions of the present invention (e.g., primary transition metal compositions) include the transition metal in a non-metallic form (i.e., in a non-zero oxidation state) combined with nitrogen, carbon, or carbon and nitrogen in form of a transition metal nitride, carbide, or carbide-nitride, respectively. The transition metal compositions may further comprise free transition metal in its metallic form (i.e., in an oxidation state of zero) . Similarly, catalytic compositions of the present invention (e.g., secondary catalytic compositions) include the metallic element in a non- metallic or in the case of selenium and tellurium "non- elemental" form (i.e., in a non-zero oxidation state) combined with nitrogen, carbon, or carbon and nitrogen in form of a metallic nitride, carbide, or carbide-nitride, respectively. The catalytic compositions may further comprise free metallic element (i.e., in an oxidation state of zero) . The transition metal compositions and catalytic compositions may also include carbide-nitride compositions having an empirical formula of CN_x wherein x is from about 0.01 to about 0.7.

[00113] Typically, at least about 5% by weight of the transition metal or metallic element is present in a non-zero oxidation state (e.g., as part of a transition metal nitride, transition metal carbide, or transition metal carbide-nitride) , more typically at least about 20%, still more typically at least about 30% and, even more typically, at least about 40%. Preferably, at least about 50% of the transition metal or metallic element is present in a non-zero oxidation state, more preferably at least about 60%, still more preferably at least about 75% and, even more preferably, at least about 90%. In various preferred embodiments, all or substantially all (e.g., greater than 95% or even greater than 99%) of the transition metal or metallic element is present in a non-zero oxidation state. In various embodiments, from about 5 to about 50% by weight of the transition metal or metallic element is in a nonzero oxidation state, in others from about 20 to about 40% by weight and, in still others, from about 30 to about 40% by weight of the transition metal or metallic element is in a nonzero oxidation state.

[00114] For transition metal catalysts including one or more metal compositions formed on or over the surface of a carbon support (e.g., a transition metal nitride), generally either or each composition constitutes at least about 0.1% by weight of the catalyst and, typically, at least about 0.5% by weight of the catalyst. More particularly, a transition metal composition formed on a carbon support typically constitutes from about 0.1 to about 20% by weight of the catalyst, more typically from about 0.5 to about 15% by weight of the catalyst, more typically from about 0.5 to about 10% by weight of the catalyst, still more typically from about 1 to about 12% by weight of the catalyst, and, even more typically, from about 1.5% to about 7.5% or from about 2% to about 5% by weight of the catalyst.

[00115] Generally, a transition metal constitutes at least about 0.01% by weight of the catalyst, at least about 0.1% by weight of the catalyst, at least about 0.2% by weight of the catalyst, at least about 0.5% by weight of the catalyst, at least about 1% by weight of the catalyst, at least about 1.5% by weight of the catalyst, or at least 1.6% by weight of the transition metal catalyst. Typically, the transition metal constitutes at least about 1.8% by weight of the catalyst and, more typically, at least about 2.0% by weight of the catalyst. In accordance with these and other embodiments, the transition metal generally constitutes less than about 10% by weight of the catalyst or less than about 5% by weight of the catalyst. In certain embodiments, the transition metal typically constitutes from about 0.5% to about 3%, more typically from about 1% to about 3% or from about 1.5% to about 3% by weight of the catalyst. In various other embodiments, the transition metal constitutes between 1.6% and 5% or between 2% and 5% by weight of the catalyst.

[00116] The nitrogen component of the metal compositions (e.g., primary or secondary transition metal compositions) is generally present in a proportion of at least about 0.01% by weight of the catalyst, more generally at least about 0.1% by weight of the catalyst and, still more generally, at least about 0.5% or at least about 1% by weight of the catalyst. Typically, the nitrogen constitutes at least about 1.0%, at least about 1.5%, at least about 1.6%, at least about 1.8%, or at least about 2.0% by weight of the catalyst. More typically, the nitrogen component is present in a proportion of from about 0.1 to about 20% by weight of the catalyst, from about 0.5% to about 15 by weight of the catalyst, from about 1% to about 12% by weight of the catalyst, from about 1.5% to about 7.5% by weight of the catalyst, or from about 2% to about 5% by weight of the catalyst. It has been observed that catalyst activity and/or stability may decrease as nitrogen content of the catalyst increases. Increasing the proportion of nitrogen in the catalyst may be due to a variety of factors including, for example, use of a nitrogen-containing source of transition metal .

[00117] The secondary metallic element of a secondary catalytic composition is generally present in a proportion of at least about 0.01% by weight of the catalyst, more generally at least about 0.1% by weight of the catalyst or at least about 0.2% by weight of the catalyst. Typically, the secondary metallic element is present in a proportion of at least about 0.5% by weight of the catalyst and, more typically, at least about 1% by weight of the catalyst. Preferably, the secondary metallic element is present in a proportion of from about 0.1 to about 20% by weight of the catalyst, more preferably from about 0.5 to about 10% by weight of the catalyst, still more preferably from about 0.5 to about 2% by weight of the catalyst and, even more preferably, from about 0.5 to about 1.5% by weight of the catalyst.

[00118] For example, in various such embodiments, titanium is present in a proportion of about 1% by weight of the catalyst. In various embodiments, titanium is preferably present in a proportion of from about 0.5 to about 10% by weight of the catalyst, more preferably from about 0.5 to about 2% by weight of the catalyst and, even more preferably, from about 0.5 to about 1.5% by weight of the catalyst. In other embodiments, titanium is preferably present in a proportion of from about 0.1 to about 5% by weight of the catalyst, more preferably from about 0.1 to about 3% by weight of the catalyst and, even more preferably, from about 0.2 to about 1.5% by weight of the catalyst. Often, titanium is present in a proportion of about 1% by weight of the catalyst.

1. Nitrides

[00119] In various embodiments a transition metal composition comprising a transition metal and nitrogen comprises a transition metal nitride. For example, a transition metal/nitrogen composition comprising cobalt and nitrogen typically comprises cobalt nitride. Such cobalt nitride typically has an empirical formula of, for example, CoN_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one cobalt nitride having such an empirical formula (e.g., C0₂N) is at least about 0.01% by weight of the catalyst. Typically, the total proportion of all cobalt nitrides having such an empirical formula is at least about 0.1% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. In such embodiments, cobalt may typically be present in a proportion of at least about 0.1% by weight of the catalyst, more typically at least about 0.5% by weight of the catalyst and, even more typically, at least about 1% by weight of the catalyst. By way of further example, a transition metal/nitrogen composition comprising iron and nitrogen typically comprises iron nitride. Such iron nitride typically has an empirical formula of, for example, FeN_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one iron nitride having such an empirical formula (e.g., FeN) is present in a proportion of at least about 0.01% by weight of the catalyst. Typically, the total proportion of all iron nitrides having such an empirical formula is at least about 0.1% by weight of the catalyst. In such embodiments, iron may typically be present in a proportion of at least about 0.01% by weight of the catalyst, more typically at least about 0.1% by weight of the catalyst, more typically at least about 0.2% by weight of the catalyst, even more typically at least about 0.5% by weight of the catalyst and, still more typically, at least about 1% by weight of the catalyst.

[00120] In further embodiments, a transition metal/nitrogen composition comprises molybdenum and nitrogen and, in a preferred embodiment, comprises molybdenum nitride. Typically, any molybdenum nitride formed on the carbon support as part of a transition metal composition comprises a compound having a stoichiometric formula of M0₂N. In addition, transition metal/nitrogen compositions formed on the carbon support may comprise tungsten and nitrogen and, more particularly, comprise tungsten nitride. Typically, any tungsten nitride formed on the carbon support as part of the transition metal composition comprises a compound having a stoichiometric formula of W₂N.

[00121] In certain embodiments in which a transition metal composition comprises a primary transition metal (e.g., cobalt or iron) and nitrogen, the transition metal composition further comprises a secondary transition metal (e.g., titanium) or other secondary metallic element (e.g., magnesium, selenium, or tellurium) . The primary transition metal and nitrogen are typically present in these embodiments in the proportions set forth above concerning transition metal compositions generally. In the case of titanium as the secondary transition metal, the transition metal composition typically includes titanium cobalt nitride or titanium iron nitride and, in particular, titanium cobalt nitride or titanium iron nitride having an empirical formula of TiCo_yN_x or TiFe_yN_x, respectively, wherein each of x and y is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. In various other embodiments a metal composition (e.g., a primary transition metal composition or secondary catalytic composition) comprises a compound or complex of a secondary metallic element and nitrogen, e.g., a secondary transition metal nitride such as titanium nitride. More particularly, these compositions typically comprise titanium nitride which has an empirical formula of, for example, TiN_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one titanium cobalt nitride (e.g., TiCoN₂), titanium iron nitride (e.g., TiFeN₂), and/or titanium nitride (e.g., TiN) having such an empirical formula is at least about 0.01% by weight of the catalyst. Typically, the total proportion of all titanium cobalt nitrides, titanium iron nitrides, and/or titanium nitrides having such an empirical formula is at least about 0.1% by weight of the catalyst.

2. Carbides

[00122] In various embodiments a transition metal composition comprising a transition metal and carbon comprises a transition metal carbide. For example, a transition metal/carbon composition comprising cobalt and carbon typically comprises cobalt carbide. Such cobalt carbide typically has an empirical formula of, for example, CoC_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one cobalt carbide having such an empirical formula (e.g., Co₂C) is at least about 0.01% by weight of the catalyst. Typically, the total proportion of all cobalt carbide (s) having such an empirical formula is at least about 0.1% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. In such embodiments, cobalt may generally be present in a proportion of at least about 0.1% by weight of the catalyst, at least about 0.5% by weight of the catalyst, or at least about 1% by weight of the catalyst. Typically, cobalt may be present in a proportion of from about 0.5 to about 10% by weight of the catalyst, more typically from about 1 to about 2% by weight of the catalyst and, still more typically, from about 1 to about 1.5% by weight of the catalyst. In certain embodiments, cobalt may be present in a proportion of from about 0.1 to about 3% by weight of the catalyst. By way of further example, a transition metal/carbon composition comprising iron and carbon typically comprises iron carbide. Such iron carbide typically has an empirical formula of, for example, FeC_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one iron carbide having such an empirical formula (e.g., Fθ3C) is at least about 0.01% by weight of the catalyst. Typically, the total proportion of all iron carbide (s) having such an empirical formula is at least about 0.1% by weight of the catalyst. In such embodiments, iron is generally present in a proportion of at least about 0.01% by weight of the catalyst or at least about 0.1% by weight of the catalyst. Typically, iron is present in a proportion of from about 0.1% to about 5% by weight of the catalyst, more typically from about 0.2% to about 1.5% by weight of the catalyst and, still more typically, from about 0.5 to about 1% by weight of the catalyst.

[00123] In further embodiments, a transition metal/carbon composition comprises molybdenum and carbon and, in a preferred embodiment, comprises molybdenum carbide. Typically, molybdenum carbide formed on the carbon support as part of a transition metal composition comprises a compound having a stoichiometric formula of M0₂C. In other embodiments, a transition metal/carbon composition comprises tungsten and carbon and, in a preferred embodiment, comprises tungsten carbide. Typically, tungsten carbide formed on the carbon support as part of the primary transition metal composition comprises a compound having a stoichiometric formula of WC or W₂C. In certain embodiments in which a transition metal composition comprises a primary transition metal (e.g., cobalt or iron) and carbon, the transition metal composition further comprises a secondary transition metal (e.g., titanium) or other secondary metallic element (e.g., magnesium, selenium or tellurium) . The primary transition metal is typically present in these embodiments in the proportions set forth above concerning transition metal compositions generally. In the case of titanium as a secondary transition metal, the transition metal composition typically includes titanium cobalt carbide or titanium iron carbide and, in particular, titanium cobalt carbide or titanium iron carbide having an empirical formula of TiCo_yC_x or TiFe_yC_x, respectively, wherein each of x and y is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. In various other embodiments the transition metal composition comprises a compound or complex of the secondary metal and carbon, e.g., a secondary transition metal carbide such as titanium carbide. More particularly, these compositions typically comprise titanium carbide which has an empirical formula of, for example, TiC_x wherein x is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. Typically, the total proportion of at least one titanium cobalt carbide (e.g., TiCoC₂), titanium iron carbide (e.g., TiFeC₂), or titanium carbide (e.g., TiC) having such an empirical formula is at least about 0.01% by weight of the catalyst. Typically, the total proportion of all titanium cobalt carbide or titanium iron nitride having such an empirical formula is at least about 0.1% by weight of the catalyst .

[00124] Titanium is generally present in such embodiments in a proportion of at least about 0.01% by weight of the catalyst, typically at least about 0.1% by weight of the catalyst, more typically at least about 0.2% by weight of the catalyst, still more typically at least about 0.5% by weight of the catalyst and, even more typically, at least about 1% by weight of the catalyst .

[00125] In various embodiments (e.g., titanium cobalt carbide or titanium carbide) , titanium is preferably present in a proportion of from about 0.5 to about 10% by weight of the catalyst, more preferably from about 0.5 to about 2 by weight of the catalyst, still more preferably from about 0.5 to about 1.5% by weight of the catalyst and, even more preferably, from about 0.5 to about 1.0% by weight of the catalyst. In other embodiments (e.g., titanium iron carbide or titanium carbide), titanium is preferably present in a proportion of from about 0.1 to about 5% by weight of the catalyst, more preferably from about 0.1 to about 3% by weight of the catalyst, more preferably from about 0.2 to about 1.5% by weight of the catalyst and, still more preferably, from about 0.5 to about 1.5% by weight of the catalyst.

3. Carbide and Nitride and Carbide-Nitrides [00126] In various embodiments a transition metal composition comprises a transition metal, nitrogen, and carbon and, in such embodiments, may comprise a transition metal nitride and/or a transition metal carbide. For example, a transition metal composition comprising cobalt, carbon, and nitrogen may comprise cobalt carbide and cobalt nitride having empirical formulae as set forth above specifically describing cobalt carbide and/or cobalt nitride. Similarly, either or each of cobalt carbide and cobalt nitride, cobalt, and nitrogen are typically present in the proportions in terms of percent by weight of the catalyst set forth above specifically describing cobalt carbide and/or cobalt nitride. By way of further example, a transition metal composition comprising iron, carbon, and nitrogen may comprise iron carbide and iron nitride having empirical formulae as set forth above specifically describing iron carbide and/or iron nitride. Similarly, either or each of iron carbide and iron nitride, iron, and nitrogen are typically present in the proportions in terms of percent by weight of the catalyst set forth above specifically describing iron carbide and/or iron nitride.

[00127] Additionally or alternatively, a transition metal composition comprising a transition metal, nitrogen and carbon may comprise a transition metal carbide-nitride. For example, a transition metal composition comprising cobalt, carbon, and nitrogen may include cobalt carbide-nitride having an empirical formula of CoC_yN_x, where x and y are typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. For example, CoCN or C0C₂N may be present. Typically, a cobalt carbide-nitride having such an empirical formula is present in a proportion of at least about 0.01% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. Typically, the total proportion of all cobalt carbide-nitrides of such empirical formula is at least about 0.1% by weight of the catalyst. In such embodiments, cobalt is typically present in the proportions set forth above specifically describing cobalt nitride and/or cobalt carbide. Likewise, nitrogen is typically present in such embodiments in the proportions set forth above specifically describing cobalt nitride. By way of further example, a transition metal composition comprising iron, carbon, and nitrogen may include iron carbide-nitride having an empirical formula of FeC_yN_x, where x and y are typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. For example, FeCN or FeC₂N may be present. Typically, an iron carbide-nitride having such an empirical formula is present in a proportion of at least about 0.01% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. Typically, the total proportion of all iron carbide-nitrides of such empirical formula is at least about 0.1% by weight of the catalyst. In such embodiments, iron is typically present in the proportions set forth above specifically describing iron nitride and/or iron carbide. Likewise, nitrogen is typically present in such embodiments in the proportions set forth above specifically describing iron nitride.

[00128] In various embodiments in which the transition metal composition comprises a transition metal, nitrogen and carbon, the transition metal composition comprises a transition metal carbide, a transition metal nitride and a transition metal carbide-nitride. For example, catalysts of the present invention may comprise cobalt carbide, cobalt nitride, and cobalt carbide-nitride. In such embodiments, typically the total proportion of such carbide (s), nitride (s), and carbide- nitride (s) is at least about 0.1% by weight of the catalyst and, still more typically, from about 0.1 to about 20% by weight of the catalyst. By way of further example, catalysts of the present invention may comprise iron carbide, iron nitride, and iron carbide-nitride. In such embodiments, typically the total proportion of such carbide (s), nitride (s), and carbide- nitride (s) is at least about 0.1% by weight of the catalyst and, still more typically, from about 0.1 to about 20% by weight of the catalyst.

[00129] In certain embodiments in which a transition metal composition comprises a primary transition metal (e.g., cobalt or iron) , nitrogen, and carbon, the transition metal composition further comprises a secondary metallic element (e.g., a secondary transition metal such as titanium) . Thus, the transition metal composition may include, for example, titanium cobalt carbide and/or titanium cobalt nitride. In particular, the transition metal composition may comprise titanium cobalt carbide and/or titanium cobalt nitride having empirical formulae as set forth above specifically describing titanium cobalt carbide and/or titanium cobalt nitride. Similarly, either or each of titanium cobalt carbide and titanium cobalt nitride are present in the proportions in terms of percent by weight of the catalyst set forth above specifically describing titanium cobalt carbide and/or titanium cobalt nitride. Cobalt, titanium, and nitrogen are typically present in these embodiments in the proportions set forth above concerning transition metal/nitrogen/carbon compositions generally comprising cobalt, titanium, nitrogen and/or carbon. Additionally or alternatively, the transition metal composition may include titanium cobalt carbide-nitride including, for example, titanium cobalt carbide-nitride having an empirical formula of TiCo_zC_yN_x, wherein each of x, y and z is typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. For example, TiCoCN may be present. Typically, a titanium cobalt carbide-nitride having such an empirical formula is present in a proportion of at least about 0.01% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. Typically, the total proportion of all titanium cobalt carbide-nitrides of such empirical formula is at least about 0.1% by weight of the catalyst. Cobalt, titanium, and nitrogen are typically present in these embodiments in the proportions set forth above concerning transition metal/nitrogen/carbon compositions generally comprising cobalt, titanium, nitrogen and/or carbon. In various embodiments, the transition metal catalyst may comprise titanium cobalt carbide, titanium cobalt nitride, and titanium cobalt carbide-nitride. In such embodiments, typically the total proportion of such carbide (s) , nitride (s), and carbide-nitride (s) is at least about 0.1% by weight of the catalyst and, still more typically, from about 0.1 to about 20% by weight of the catalyst.

[00130] Transition metal compositions comprising iron, nitrogen, and carbon may also further comprise titanium. In these embodiments, the transition metal composition includes, for example, titanium iron carbide and/or titanium iron nitride. In particular, the transition metal composition may comprise titanium iron carbide and titanium iron nitride having empirical formulae as set forth above specifically describing titanium iron carbide and/or titanium iron nitride. Similarly, either or each of titanium iron carbide and titanium iron nitride are present in the proportions in terms of percent by weight of the catalyst set forth above specifically describing titanium iron carbide and/or titanium iron nitride. Iron, titanium, and nitrogen are typically present in these embodiments in the proportions set forth above concerning transition metal/nitrogen/carbon compositions generally comprising iron, titanium, nitrogen and/or carbon.

[00131] In various other embodiments a transition metal composition comprising titanium, iron, carbon, and nitrogen may include titanium iron carbide-nitride having an empirical formula of TiFe_zC_yN_x, where x, y and z are typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. For example, TiFeCN may be present. Typically, a titanium iron carbide- nitride having such an empirical formula is present in a proportion of at least about 0.01% by weight of the catalyst and, more typically, from about 0.1 to about 0.5% by weight of the catalyst. Typically, the total proportion of all titanium iron carbide-nitrides of such empirical formula is at least about 0.1% by weight of the catalyst.

[00132] Iron, titanium, and nitrogen are typically present in these embodiments in the proportions set forth above concerning transition metal/nitrogen/carbon compositions generally comprising iron, titanium, nitrogen and/or carbon.

[00133] In various embodiments, the catalyst may comprise titanium iron carbide, titanium iron nitride, and titanium iron carbide-nitride. In such embodiments, typically the total proportion of such carbide (s), nitride (s), and carbide- nitride (s) is at least about 0.1% by weight of the catalyst and, still more typically, from about 0.1 to about 20% by weight of the catalyst.

[00134] In various other embodiments, a secondary metallic element composition (e.g., a secondary catalytic composition) comprises, for example, tellurium or a transition metal such as titanium. Thus, in certain embodiments the secondary catalytic composition comprises titanium, carbon and nitrogen. More particularly, in these embodiments the secondary catalytic composition may comprise titanium carbide (e.g., TiC) and/or titanium nitride (e.g., TiN) having empirical formula as set forth above specifically describing titanium carbide and/or titanium nitride. Similarly, either or each of titanium carbide and titanium nitride, titanium, and nitrogen, are typically present in the proportions in terms of percent by weight of the catalyst set forth above specifically describing titanium carbide and/or titanium nitride.

[00135] In various other embodiments a transition metal composition comprising titanium, cobalt, carbon, and nitrogen may include titanium carbide-nitride having an empirical formula of TiC_yN_x, where x and y are typically from about 0.25 to about 4, more typically from about 0.25 to about 2 and, still more typically, from about 0.25 to about 1. For example, TiCN may be present. Typically, a titanium carbide-nitride having such an empirical formula is present in a proportion of at least about 0.01% by weight of the catalyst and, more typically, from about 0.1% to about 0.5% by weight of the catalyst. Typically, the total proportion of all titanium carbide-nitrides of such empirical formula is at least about 0.1% by weight of the catalyst. Titanium and nitrogen are typically present in these embodiments in the proportions in terms of percent by weight of the catalyst set forth above specifically describing titanium carbide and/or titanium nitride. Similarly, cobalt is typically present in these embodiments in the proportions set forth above describing cobalt carbide and/or cobalt nitride.

[00136] In various embodiments, the transition metal catalyst may comprise titanium cobalt carbide, titanium cobalt nitride, and titanium cobalt carbide-nitride. In such embodiments, typically the total proportion of such carbide (s), nitride (s), and carbide-nitride (s) is at least about 0.1% by weight of the catalyst and, still more typically, from about 0.1 to about 20% by weight of the catalyst. Further in accordance with the present invention, a transition metal composition (e.g., a primary transition metal composition) may include a plurality of transition metals selected from the group consisting of Group IB, Group VB, Group VIB, Group VIIB, iron, cobalt, nickel, lanthanide series metals, and combinations thereof. In particular, the primary transition metal composition may include a plurality of transition metals selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, ruthenium and cerium. For example, the transition metal composition may comprise cobalt cerium nitride, cobalt cerium carbide, cobalt cerium carbide-nitride, nickel cobalt nitride, vanadium cobalt nitride, chromium cobalt nitride, manganese cobalt nitride, copper cobalt nitride.

[00137] Other bi-metallic carbide-nitrides present in transition metal compositions in accordance with the present invention may be in the form of cobalt iron carbide-nitride or cobalt copper carbide-nitride. One of such bi-transition metal compositions (e.g., a bi-transition metal nitride) may be present in a total proportion of at least about 0.1% by weight and, more typically, in a proportion of from about 0.1 to about 20% by weight of the catalyst. One or more of such bi- transition metal compositions (e.g., nitride, carbide, and/or carbide-nitride) may be present in a total proportion of at least about 0.1% by weight and, more typically, in a proportion of from about 0.1 to about 20% by weight of the catalyst. Bi- primary transition metal compositions may further comprise a secondary transition metal (e.g., titanium) in accordance with the discussion set forth above.

[00138] In certain embodiments, a transition metal composition formed on the carbon support generally comprises either or both of a composition comprising a transition metal and carbon (i.e., a transition metal/carbon composition) or a composition comprising a transition metal and nitrogen (i.e., a transition metal/nitrogen composition) in which the transition metal is selected from molybdenum and tungsten.

[00139] In various embodiments including a transition metal composition comprising either or both of a transition metal/carbon composition or a transition metal/nitrogen composition in which the transition metal is selected from molybdenum and tungsten, generally the transition metal composition constitutes at least about 5% by weight of a catalyst including a transition metal composition formed on a carbon. Typically, the transition metal composition comprises from about 5% to about 20% by weight of the catalyst, more typically from about 10% to about 15% by weight of the catalyst, and, still more typically, from about 10% to about 12% by weight of the catalyst. Generally, the transition metal component of the transition metal composition (i.e., molybdenum or tungsten and nitrogen and/or carbon) comprises at least about 5% by weight of the catalyst. Preferably, the transition metal component of the transition metal composition comprises from about 8% to about 15% by weight of the catalyst. C. Processes for Preparation of the Transition Metal

Catalyst

[00140] As noted, transition metal catalysts of the present invention include at least one transition metal composition comprising one or more transition metals, nitrogen, and/or carbon formed on or over the surface of a carbon support. The transition metal composition may comprise a single compound or a mixture of compounds including, for example, transition metal nitrides, transition metal carbides, and transition metal carbide-nitrides. Generally, the transition metal composition is present in the form of discrete particles and/or a film (e.g., an amorphous or crystalline film) . Regardless of the precise chemical structure of the transition metal composition, in various embodiments a substantial portion of the transition metal and nitrogen of the transition metal composition are believed to be present in either an amorphous film or in discrete particles. In the case of a transition metal composition comprising discrete particles, preferably a substantial portion of the transition metal and nitrogen of the transition metal composition are present in discrete particles.

[00141] The transition metal composition is formed on a carbon support by heating the carbon support having a precursor composition thereon, typically in the presence of a nitrogen- containing environment. Two competing events are believed to be occurring during heat treatment of the precursor composition, although, depending on the conditions, one can prevail substantially to the exclusion of the other. One of these processes comprises formation of elemental metal, e.g., metallic cobalt, which tends to aggregate into relatively large metallic particles. The other is the generation of a form of a metal nitride that develops in a physical form comprising relatively fine crystallites, a crystalline film, and/or an amorphous film. Without being bound to a particular theory, there is evidence that the transition metal/nitrogen composition comprises a crystalline or quasi-crystalline metal lattice wherein the metal atoms are ionized to a substantial degree, e.g., in the case of cobalt, a substantial fraction of the cobalt is present as Co⁺². Nitrogen is believed to be dispersed in the interstices of the metal lattice, apparently in the form of nitride ions and/or as nitrogen co-ordinated to the metal or metal ions. In this regard, the dispersion of nitrogen in the transition metal composition may be comparable to, or in any event analogized to, the dispersion of carbon or carbide in Fe structure of steel, although the nitrogen content of the transition metal composition may likely be somewhat greater than the carbon content of steel. The exact structure of the transition metal/nitrogen composition is complex and difficult to precisely characterize, but evidence consistent with the structural characteristics described above is consistent with X-Ray Photoelectron Spectroscopy (XPS) , Electron Paramagnetic Resonance (EPR) Spectroscopy, and particle size data obtained on the catalysts.

[00142] The incidence of relatively large particles generally increases as the proportion of metal ions of the precursor composition in close proximity at the surface of the carbon support increases; a substantial portion of relatively large particles is preferably avoided due to the attendant reduction in catalytic surface area, and further because the larger particles are believed to be largely constituted of catalytically inactive elemental metal. Formation of the transition metal composition is generally promoted in preference to formation of relatively large metal particles by relatively sparse precursor composition dispersion that allows access of the nitrogen-containing environment to the metal particles. Thus, the size distribution of particles comprising the transition metal composition, and/or the distribution of such composition between discrete particles and an amorphous film is currently believed to be a function of the dispersion of metal ions of the precursor composition. In accordance with the present invention, various novel processes have been discovered for the preparation of active transition metal catalysts. These preparation processes are believed to contribute to advantageous (i.e., relatively sparse) dispersion of metal ions of the precursor composition at a given metal loading and, consequently, minimize, and preferably substantially eliminate, formation of a substantial portion of relatively large particles (e.g., particles of a size greater than 20 nm, 30 nm, or 40 nm in their largest dimension) while promoting formation of the transition metal composition (e.g., a transition metal nitride) . These processes include, for example, selection of certain preferred compounds as the source of transition metal, contacting the carbon support with solvents such as a coordinating solvent, a solvent having a polarity less than that of water and/or a solvent having a surface tension less than that of water, and treatment of the carbon support.

[00143] Formation of a substantial portion of relatively large metal particles generally increases with metal loading and the detrimental effect of such particles on catalytic activity thus tends to increase as metal loading increases. Where the precursor composition is deposited from a liquid medium consisting only of water, increases in metal loading beyond a threshold level may result in formation of a substantial portion of relatively large particles and, thus, negate any appreciable gain in catalytic activity that might otherwise result from the presence of a larger concentration of metal. Advantageously, the techniques described herein allow the use of higher metal loadings (e.g., greater than 1.6%, greater than 1.8%, greater than 2.0%, up to about 2.5%, or even up to about 3%, by weight of the catalyst, or greater) while avoiding formation of a substantial portion of relatively large particles and the attendant reduction in catalytic surface area.

1. Formation of Transition Metal Composition Precursor [00144] In processes for forming a transition metal composition (e.g., forming a transition metal composition or secondary catalytic composition on or over the surface of a carbon support and/or on or over the surface of a metal composition) , generally a precursor of the transition metal composition is formed on the carbon support by contacting the carbon support with a source of the transition metal and a liquid medium, typically in a mixture that comprises the liquid medium. During precursor formation, transition metal source compound is typically dispersed and/or dissolved in a liquid medium (e.g., an aqueous medium such as water) and transition metal ions are solvated in the liquid medium (i.e., transition metal ions are bound to one or more molecules of the liquid medium) . The precursor composition may typically comprise solvated ions which may be deposited on and/or bound to the carbon support (i.e., the precursor composition may comprise a metal ion bonded to the carbon support and/or molecules of a liquid medium) . The pre-treated carbon support is then subjected to further treatment (e.g., elevated temperature) to provide a transition metal composition and/or discrete particles on the carbon support .

Transition Metal Sources

[00145] The dispersion of metal ions of the precursor composition on the carbon support and, likewise, the size of discrete particles formed upon treatment of the precursor composition, may be affected by the structure of the source compound (e.g., transition metal salt), in particular the amount of space occupied by the structure of the transition metal salt (i.e., its relative bulk). The distribution of the transition metal composition between discrete particles and an amorphous film formed upon treatment of the precursor composition may also be affected by the structure of the source compound. For example, transition metal salts containing relatively large anions (e.g., an octanoate as compared to a halide salt) are believed to conduce to more sparse dispersion of metal centers of the precursor composition.

[00146] Generally, the source compound comprises a salt of the transition metal. Typically, the source compound is in the form of a water-soluble transition metal salt comprising a metal cation and an anion such as, for example, carbonate, halide, sulfate, nitrate, acetlyacetonate, phosphate, formate, orthoformate, carboxylate, and combinations thereof, or an anion comprising a transition metal and a cation such as ammonium or alkali metal. In various embodiments, the transition metal source comprises a transition metal carboxylate salt such as an acetate, formate, octanoate, or combinations thereof. The source compound is also preferably soluble in a polar organic solvent such as a lower alcohol and/or in a coordinating (e.g., chelating) solvent such as glyme, diglyme, or other coordinating solvents described below, or at least in aqueous mixtures comprising such polar organic solvents and/or coordinating solvents .

[00147] In the case of a transition metal source comprising iron, the transition metal salt is typically an iron halide (e.g., FeCl₂ or FeCl₃), iron sulfate (e.g., FeSO₄), iron acetate, ferrocyanide (e.g., ammonium ferrocyanide, (NH₄) ₄Fe (CN) ₆) , ferricyanide, or combinations thereof.

[00148] In the case of a transition metal source comprising cobalt, the transition metal salt may typically be a cobalt halide (e.g., CoCl₂), a cobalt sulfate (e.g., CoSO₄), cobalt nitrate (i.e., Co(NOs)₂), cobalt acetate, cobalt acetylacetonate (e.g., C0C10H14O4) , cobalt octanoate, a cobalt formate, a cobalt orthoformate, or combinations thereof.

[00149] By way of further example, to produce a transition metal composition comprising titanium, the source compound may typically comprise a titanium sulfate (e.g., Ti₂ (SO₄) 3), titanium oxysulfate (TiO(SO₄)), a titanium halide (e.g., TiCl₄), a titanium alkoxide, or a combination thereof.

[00150] In the case of transition metal compositions comprising tungsten or molybdenum, the source compound may conveniently be a salt that comprises an anion containing highly oxidized molybdenum or tungsten, for example, a molybdate or tungstate salt. Heteromolybdates and heterotungstates, such as phosphomolybdates and phosphotungstates are also suitable, as are molybdophosphoric acid and tungstophosphoric acid. In most of these, the molybdenum or tungsten is hexavalent . Where a salt is used, it is preferably selected from among those that are water-soluble or those soluble in a polar organic solvent such as a lower alcohol and/or in a coordinating (e.g., chelating) solvent, so that the cation is most typically sodium, potassium or ammonium. Salts comprising molybdenum or tungsten cations may also be used, but the molybdates and tungstates are generally the more convenient sources.

[00151] Other types of transition metal-containing compounds including, for example, carbonates (e.g., CoCO₃) or oxides of the transition metal (e.g., CoO) may be used in processes for depositing the transition metal. While these types of compounds are generally less soluble in deposition liquid media suitable for use in the processes detailed herein than the sources previously detailed, they may be acidified by reaction with, for example, hydrochloric acid to provide a source of transition metal that is more soluble in the deposition liquid medium (e.g., C0CI₂) . Operation in this manner may be advantageous in commercial preparation of the catalyst due to the relatively low cost and availability of these types of cobalt-containing compounds, particularly cobalt carbonate. It should be understood that reference to a "source" of transition metal throughout the present specification and claims thus encompasses these types of transition metal-containing compounds.

[00152] It is currently believed that sulfates, nitrates, ammonium salts, octanoates, and acetyloctanoates are "bulkier" than halide salts. Thus, in various preferred embodiments the source of transition metal is selected from the group consisting of sulfates, nitrates, ammonium salts, octanoates, acetyloctanoates and combinations thereof. However, it should be understood that using source compounds comprising halide salts provides active catalysts as well.

[00153] A mixture comprising a source of the transition metal (i.e., a source compound) and a liquid medium, optionally comprising one or more solvents, may be contacted with a carbon support. Advantageously, this may be accomplished by preparing a slurry of a particulate carbon support in a liquid medium (e.g., water), and adding to the slurry a mixture containing a source of the transition metal (e.g., a transition metal salt). Alternatively, an aqueous slurry containing a particulate carbon support can be added to a mixture containing a transition metal salt and a liquid medium, the liquid medium optionally, but preferably comprising one or more solvents. A further alternative involves adding the carbon support (e.g., neat carbon support) to a mixture containing a transition metal salt and a liquid medium, the liquid medium optionally comprising one or more solvents.

[00154] The relative proportions of source compound contacted with the carbon support, or present in a mixture or slurry contacted with the carbon support, are not narrowly critical. Overall, a suitable amount of source compound should be added to any slurry or mixture containing the carbon support to provide sufficient transition metal deposition.

[00155] Typically, the source compound is present in a mixture or slurry containing the source compound and a liquid medium in a proportion of at least about 0.01 g/liter and, more typically, from about 0.1 to about 10 g/liter. The carbon support is typically present in the suspension of slurry in a proportion of at least about 1 g/liter and, more typically, from about 1 g/liter to about 50 g/liter. Additionally or alternatively, the liquid medium generally contains the source of transition metal at a concentration of at least about 0.1% by weight, at least about 0.2% by weight, or at least about 0.5% by weight. Typically, the metal is present in the liquid medium at a concentration of from about 0.1% to about 8% by weight, more typically from about 0.2% to about 5% by weight and, still more typically, at a concentration of from about 0.5% to about 3% by weight .

[00156] Preferably, the source compound and carbon support are present in the suspension or slurry at a weight ratio of transition metal/carbon in the range of from about 0.1 to about 20 and, more preferably, from about 0.5 to about 10.

[00157] The rate of addition of a transition metal source (e.g., a transition metal-containing salt, typically a salt solution having a concentration of approximately 0.1 molar (M) ) to a slurry containing the carbon support is not narrowly critical but, typically, the source compound is added to the carbon support mixture at a rate of at least about 0.05 millimoles (mmoles) /minute/liter and, more typically, at a rate of from about 0.05 to about 0.5 mmoles/minute/liter . Generally, at least about 0.05 L/hour per L slurry (0.05 gal. /hour per gal. of slurry) of salt solution is added to the slurry, preferably from about 0.05 L/hour per L slurry (0.05 gal. /hour per gal. of slurry) to about 0.4 L/hour per L slurry (0.4 gal. /hour per gal. of slurry) and, more preferably, from about 0.1 L/hour per L of slurry (0.1 gal . /hour per gal. of slurry) to about 0.2 L/hour per L of slurry (0.2 gal . /hour per gal. of slurry) of salt solution is added to the slurry containing the carbon support.

[00158] In various embodiments, transition metal is present in the source compound as the cation (e.g., FeCl3, C0CI₂, or Co(NC>3)2) • As the pH of the liquid medium increases, the transition metal cation of the source compound becomes at least partially hydrolyzed. For example, in the case of FeCl3, iron hydroxide ions such as Fe(OH)₂ ⁺¹ or Fe(OH)⁺² may form and, in the case of C0CI2 or Co(NOs)₂, cobalt hydroxide ions such as Co(OH)⁺¹ may form.

[00159] Such ions are adsorbed onto the negatively charged carbon support surface. Preferably, the ions diffuse into the pores and are adsorbed and dispersed throughout the surface of the carbon support, including the surfaces within the pores. However, if the pH of the liquid medium is increased too rapidly, a metal hydroxide may precipitate in the liquid medium. Conversion of the transition metal ions to neutral metal hydroxide removes the electrostatic attraction between transition metal and the carbon support surface, and thus reduces deposition of metal on the support surface. Precipitation of hydroxide into the liquid medium may also impede dispersion of metal ions throughout the pores of the carbon support surface. Thus, preferably the pH of the liquid medium is controlled to avoid rapid precipitation of transition metal hydroxides before the occurrence of sufficient deposition of transition metal onto the carbon support surface by virtue of the electrostatic attraction between transition metal ions and the carbon support surface. After sufficient deposition of transition metal onto the carbon support surface, the pH of the liquid medium may be increased at a greater rate since a reduced proportion of transition metal remains in the bulk liquid phase. [00160] The temperature of the liquid medium may also affect the rate of precipitation of transition metal, and the attendant deposition of transition metal onto the carbon support. Generally, the rate of precipitation increases as the temperature of the medium increases. Typically, the temperature of the liquid medium during introduction of the source compound is maintained in a range from about 10⁰C to about 30⁰C and, more typically, from about 20°C to about 25°C.

[00161] The initial pH and temperature levels of the liquid medium when metal begins to deposit onto the carbon support and levels to which they are increased generally depend on the transition metal cation. For example, in certain embodiments in which the transition metal is cobalt, the pH of the liquid medium is initially generally from about 7.5 to about 8.0 and typically increased to at least about 8.5, in others to at least about 9.0 and, in still other embodiments, to at least about 9.0. Further in accordance with such embodiments, the temperature of the liquid medium is initially generally about 25°C and typically increased to at least about 40⁰C, more generally to at least about 45°C and, still more generally, to at least about 50⁰C. Typically, the temperature is increased at a rate of from about 0.5 to about 10°C/min and, more typically, from about 1 to about 5°C/min. After an increase of the temperature and/or pH of the liquid medium, typically the medium is maintained under these conditions for a suitable period of time to allow for sufficient deposition of transition metal onto the carbon support surface. Typically, the liquid medium is maintained at such conditions for at least about 2 minutes, more typically at least about 5 minutes and, still more typically, at least about 10 minutes. In particular, in such embodiments, the temperature of the liquid medium is typically initially about 25°C and the pH of the liquid medium is maintained at from about 7.5 to about 8.0 during addition of the source compound. After addition of the source compound is complete, the liquid medium is agitated by stirring for from about 25 to about 35 minutes while its pH is preferably maintained at from about 7.5 to about 8.5. The temperature of the liquid medium is then preferably increased to a temperature of from about 40⁰C to about 50⁰C at a rate of from about 1 to about 5°C/min while the pH of the liquid medium is maintained at from about 7.5 to about 8.5. The medium may then be agitated by stirring for from about 15 to about 25 minutes while the temperature of the liquid medium is maintained at from about 40⁰C to about 50⁰C and the pH at from about 7.5 to about 8.0. The slurry may then be heated to a temperature of from about 50⁰C to about 55°C and its pH adjusted to from about 8.5 to about 9.0, with these conditions being maintained for approximately 15 to 25 minutes. Finally, the slurry may be heated to a temperature of from about 55°C to about 65°C and its pH adjusted to from about 9.0 to about 9.5, with these conditions maintained for approximately 10 minutes.

[00162] Regardless of the presence of a primary transition metal, secondary transition metal, or other secondary metallic element in the source compound as an anion or cation, in order to promote contact of the support with the transition metal source compound, and mass transfer from the liquid phase, the slurry may be agitated concurrently with additions of source compound to the slurry or after addition of the transition metal salt to the slurry is complete. The liquid medium may likewise be agitated prior to, during, or after operations directed to increasing its temperature and/or pH. Suitable means for agitation include, for example, by stirring or shaking the slurry.

[00163] For transition metal compositions comprising a plurality of metals (e.g., a transition metal composition comprising a plurality of primary transition metals or a transition metal composition comprising a primary transition metal and a secondary metallic element) , typically a single source compound comprising all of the metals, or a plurality of source compounds each containing at least one of the metals or other metallic elements is contacted with the carbon support in accordance with the preceding discussion. Formation of precursors of the transition metal (s) or other metallic element (s) may be carried out concurrently (i.e., contacting the carbon support with a plurality of source compounds, each containing the desired element for formation of a precursor) or sequentially (formation of one precursor followed by formation of one or more additional precursors) in accordance with the above discussion.

[00164] After the source of the transition metal or other secondary element has contacted the support for a time sufficient to ensure sufficient deposition of the source compound (s) and/or formation of its (their) derivative (s) , the slurry is filtered, the support is washed with an aqueous solution and allowed to dry. Typically, the source contacts a porous support for at least about 0.5 hours and, more typically, from about 0.5 to about 5 hours, so that the support becomes substantially impregnated with a solution of the source compound. Generally, the impregnated support is allowed to dry for at least about 2 hours. Preferably, the impregnated support is allowed to dry for from about 5 to about 12 hours. Drying may be accelerated by contacting the impregnated carbon support with air at temperatures generally from about 80⁰C to about 150⁰C.

[00165] After deposition of the precursor and solids/liquid separation to recover the carbon support having the precursor thereon, the resulting filtrate or centrate, which comprises undeposited source compound, may be recovered and recycled for use in subsequent catalyst preparation protocols. For example, the transition metal content of the recovered filtrate or centrate may typically be replenished with additional transition metal source prior to use in subsequent catalyst preparation. Additionally or alternatively, the filtrate/centrate may be combined with fresh transition metal source-containing liquid medium for use in subsequent catalyst preparation.

[00166] Generally, it has been observed that deposition of transition metal in accordance with the methods detailed herein results in a relatively high proportion of the transition metal contacted with the carbon support being deposited thereon (e.g., at least about 75% by weight, at least about 90% by weight, at least about 95% by weight, or even at least about 99% by weight) . In those embodiments in which the liquid medium contacted with the carbon support includes a coordinating solvent the proportion of transition metal deposited on the carbon support generally varies with the strength of the coordination bonds formed between the transition metal and solvent-derived ligands. That is, the stronger the bonds, the lower proportion of transition metal deposited. Any such reduction in metal deposition is generally believed to be slight and, in any event, does not detract from the advantages associated with the presence of the solvent detailed elsewhere herein to any significant degree. However, in certain embodiments in which the liquid medium contacted with the carbon support includes a coordinating solvent, lesser proportions of the transition metal may deposit onto the carbon support (e.g., less than about 60% or less than about 50%) due, at least in part, to the coordinating power of the solvent. Thus, recycle and/or regeneration of the filtrate or centrate is generally more preferred in these embodiments than those in which a relatively high proportion of transition metal deposits onto the carbon support.

[00167] One consideration that may affect deposition of transition metal of the precursor composition in the "filtration" method is the partition coefficient of the transition metal between solvation in the liquid medium and adsorption on the carbon support surface to form the precursor composition. That is, deposition of transition metal over the surface of the carbon support may rely on the affinity of the transition metal ion, co-ordinated transition metal ion, or a hydrolysis product thereof, toward adsorption on the carbon surface relative to the solvating power of the liquid medium. If the partition coefficient between the liquid phase and the carbon surface is unfavorable, the filtration method may require a high ratio of source compound to carbon surface area in the deposition slurry, which in turn may require a relatively high concentration of source compound, a relatively large volume of liquid medium, or both. In any case, deposition of a sufficient quantity of source compound on the carbon surface may require a substantial excess of source compound, so that the filtrate or centrate comprises a relatively large quantity of source compound that has not deposited on the carbon but instead has been retained in the liquid medium at the equilibrium defined by the prevailing partition coefficient. Such can represent a significant yield penalty unless the filtrate can be recycled and used in depositing the precursor on fresh carbon.

Incipient Wetness Impregnation

[00168] Metal composition precursor can be deposited on the carbon support by a method using a significantly lesser proportion of liquid medium than that used in the method in which the impregnated carbon support is separated from the liquid medium by filtration or centrifugation . In particular, this alternative process preferably comprises combining the carbon support with a relative amount of liquid medium that is approximately equal to or slightly greater than the pore volume of the carbon support. In this manner, deposition of the transition metal over a large portion, preferably substantially all, of the external and internal surface of the carbon support is promoted while minimizing the excess of liquid medium. This method for deposition of metal onto a carbon support is generally referred to as incipient wetness impregnation. In accordance with this method, a carbon support having a pore volume of X is typically contacted with a volume of liquid medium that is from about 0.50X to less than about 1.25X, more typically from about 0.90X to about 1.1OX and, still more typically, a volume of liquid medium of about X. Incipient wetness impregnation generally avoids the need for separating the impregnated carbon support from the liquid medium and generates significantly less waste that must be disposed of or replenished and/or recycled for use in further catalyst preparation than in catalyst preparations utilizing higher proportions of liquid medium. Use of these lower proportions of liquid medium generally necessitates incorporating the source compound into the liquid medium at a greater concentration than in the "filtration" method. Thus, a liquid medium suitable for incipient wetness impregnation generally contains the source of transition metal at a concentration sufficient to provide a transition metal concentration therein of at least about 0.1% by weight, at least about 0.2% by weight, or at least about 0.5% by weight. Typically, an incipient wetness impregnation liquid medium contains the source of transition metal at a concentration of from about 0.1% to about 10% by weight, more typically from about 0.5% to about 7% by weight and, still more typically, at a concentration of from about 1% to about 5% by weight. One consideration that may affect deposition of transition metal of the precursor composition in the incipient wetness method is the affinity of the metal ion or coordinated metal ion for sites on the carbon support. Solvent s

[00169] Incorporation of certain polar organic solvents into a mixture or liquid medium that contacts the carbon support for deposition of the precursor composition is currently believed to provide a more sparse dispersion of metal ions than has been observed with a mixture that does not contain such a solvent (e.g., a mixture comprising a liquid medium consisting solely of water) .

Coordinating solvents

[00170] Certain polar organic solvents that have been found to provide a relatively sparse metal ion dispersion are characterized as "coordinating solvents" because they are capable of forming co-ordination compounds with various metals and metal ions, including transition metals such as cobalt, iron, etc. Thus, where the liquid medium comprises a coordinating solvent, particles or film of precursor composition deposited on the carbon support may comprise such a coordination compound. Without limiting the disclosure to a particular theory, it is believed that a coordinating solvent in fact forms a coordination compound with the metal or metal ion of the metal salt, and also binds to the carbon support, thereby promoting deposition of the precursor composition.

Coordination Compounds

[00171] Generally, a coordination compound includes an association or bond between the metal ion and one or more binding sites of one or more ligands. The coordination number of a metal ion of a coordination compound is the number of other ligand atoms linked thereto. Typically, ligands are attached to the central metal ion by one or more coordinate covalent bonds in which the electrons involved in the covalent bonds are provided by the ligands (i.e., the central metal ion can be regarded as an electron acceptor and the ligand can be regarded as an electron donor) . The typical donor atoms of the ligand include, for example, oxygen, nitrogen, and sulfur. The solvent-derived ligands can provide one or more potential binding sites; ligands offering two, three, four, etc., potential binding sites are termed bidentate, tridentate, tetradentate, etc., respectively. Just as one central atom can coordinate with more than one ligand, a ligand with multiple donor atoms can bind with more than one central atom. Coordinating compounds including a metal ion bonded to two or more binding sites of a particular ligand are typically referred to as chelates.

[00172] The stability of a coordination compound or, complex, is typically expressed in terms of its equilibrium constant for the formation of the coordination compound from the solvated metal ion and the ligand. The equilibrium constant, K, is termed the formation or, stability, constant: x metal center + y ligand > complex

K = [complex] / [metal center] ^x * [ligand] ^y [] = concentration (moles/liter)

Values for equilibrium constants reported in the literature are typically determined in an aqueous medium. Coordination compounds derived in accordance with the process of the present invention typically comprise a metal ion coordinated with one or more ligands, typically solvent-derived ligands. In various embodiments of the present invention, the coordination compound includes one or more bonds between the metal or metal ion of the transition metal source and one or more molecules of the coordinating solvent. In various such embodiments the metal or metal ion of the transition metal source is attached to the solvent-derived ligand by two bonds; thus, it may be said that the metal or metal ion is "chelated." Accordingly, in such embodiments, the coordinating solvent is properly termed a "chelating solvent." For example, in the case of a chelating solvent comprising diglyme, the metal ion is typically associated or bonded with two diglyme oxygen atoms. In various other embodiments, there may exist a bond or association between the metal ion and greater than two binding sites of a solvent- derived ligand (i.e., the coordination compound may include a tri- or tetradentate ligand such as, for example, N, N, N', N', N" pentamethyldiethylenetriamine, tartrate, and ethylene diamine diacetic acid) . In addition, metal ions of coordination compounds derived in accordance with the present invention may be associated with or bonded to a plurality of ligands . The coordination numbers of metal ions of coordination compounds derived in accordance with the present invention are not narrowly critical and may vary widely depending on the number and type of ligands (e.g., bidentate, tridentate, etc.) associated with or bonded to the metal ion.

[00173] In the embodiments wherein such a coordination compound is formed and deposited on the carbon support, such compound provides all or part of the precursor composition from which the nitride or carbide-nitride catalyst is ultimately derived. Eventually the bonds of the coordination compounds typically are broken to provide metal ions available for formation of transition metal composition by, for example, nitridation. However, the precise chemical structure of the ultimate transition metal/nitrogen composition is not known, so that the possible presence of co-ordination bonds between the metal or metal ion and carbon, oxygen, and/or nitrogen in the catalyst active phase cannot be positively excluded, and is likely. One method for breaking the coordination bonds comprises hydrolyzing the coordination complex by adjusting the pH of the liquid medium as detailed elsewhere herein concerning precursor composition deposition generally. Hydrolysis of the coordination complex (i.e., combining a metal cation with hydroxyl ions) in response to adjustments in pH of the liquid medium may generally be represented by the following:

However, it will be understood that the hydroxyl ion may not necessarily displace a ligand, but instead may exchange with another counteranion, e.g., chloride, to form the hydroxide of the co-ordinated metal ion, and such hydroxide is typically of lower solubility than the chloride so that it may precipitate on the carbon support. Alternatively, a metal/hydroxide/ligand complex as formed, for example, in accordance with the equation set out above (and shown on the right side of the equation) , may rearrange to the hydroxide of the co-ordinated metal ion. In any case, a metal oxide bond may typically be formed in deposition of the precursor composition onto the support.

[00174] As previously noted, the precursor composition generally comprises metal ions solvated by a solvent present in a liquid medium in which or in combination with which the source compound is contacted with the carbon support. In various embodiments the metal ions are solvated with water. Thus, in these embodiments, solvated metal ions are essentially separated from surrounding metal ions by at least two layers of water molecules (i.e., solvated metal ions are separated by water molecules bound thereto and water molecules bound to adjacent solvated metal ions) . When a coordinating solvent (e.g., diglyme) is present in the liquid medium, the metal ions are understood to be separated from surrounding metal ions by at least two layers of coordinating solvent molecules. Diglyme molecules, and those of other coordinating solvents that may be used in accordance with the present invention, generally occupy greater space (i.e., are generally bulkier) than water molecules. The bulkier nature of these coordination compounds as compared to water-solvated metal ions is generally due to the larger structure of the coordinating solvent molecule as compared to a water molecule. The solvent molecules thus provide a larger barrier between metal ions, and thus between precipitated metal ions or coordinated metal ions, than is provided by water molecules, such that deposited metal ions bonded to solvent molecules are more sparsely dispersed on the carbon support. A greater bond distance between metal and solvent-derived ligands of the initial coordination compound than between metal and water molecules of water-solvated ions may also contribute to a relatively sparse dispersion of metal ions. However, the effect on dispersion arising from the use of a solvent such as diglyme is believed to be due primarily to the larger structure of the coordinating solvent molecule as compared to a water molecule.

[00175] The effectiveness of any coordinating solvent that contacts the carbon support to contribute to relatively sparse precursor composition dispersion may be influenced by various features of the coordinating solvent and/or a coordination compound including a solvent-derived ligand. Where the liquid medium from which the precursor composition is deposited contains other solvents, e.g., water or a primary alcohol, one contributing feature of the coordinating solvent is its solubility in the liquid medium as a whole. Generally, coordinating solvents used in accordance with the present invention are soluble in water and/or in an aqueous medium comprising a water-soluble organic solvent (e.g., ethanol or acetone) . In particular, it is preferred for the solvent and/or compound to exhibit at least a certain degree of solubility. For example, if the coordinating solvent is not soluble in the liquid medium any coordination compound formed tends to precipitate from the liquid medium and form a physical mixture with the carbon support without sufficient deposition of the coordination compound and/or transition metal at the surface of the carbon support. Furthermore, as detailed elsewhere herein, it is preferred for the precursor composition to be deposited over a substantial portion of the porous carbon support surface, particularly the interior regions of the porous carbon substrate. If the coordination compound is not soluble to a sufficient degree to promote ingress of the coordination compound and/or transition metal into the pores of the carbon support in preference to precipitation of the metal or metal- ligand complex, a substantial portion of the coordination compound and/or transition metal may be deposited at the outer edges of the porous carbon support. Accordingly, the desired relatively sparse dispersion of precursor composition may not be achieved to a sufficient degree. However, the desired relatively sparse dispersion of precursor composition may likewise not be achieved to a sufficient degree if the coordinating solvent and/or coordination compound are soluble in the liquid medium to a degree such that the coordination compound and/or coordinated metal ion does not precipitate onto the carbon support, even in response to adjustments to the liquid medium including, for example, adjusting its pH . Accordingly, the solubility of the coordination compound and/or coordinated metal is preferably of a degree such that each of these considerations is addressed.

[00176] The strength of coordination between the coordinating solvent and transition metal also influences the effectiveness of the coordinating solvent for promoting relatively sparse precursor composition dispersion. Unless the chelating power reaches a minimum threshold, the effect of the solvent on dispersion will not be noticeable to any significant degree and the degree of coordination that prevails in the liquid medium will essentially mimic water solvation. However, if the chelating power of the coordinating solvent is too strong and does not allow coordination bonds to be broken, uncoordinated ions available for formation of the transition metal composition will not be present at the surface of the carbon support and/or hydrolysis of the metal complex may be impeded to such a degree that the coordination complex and/or metal ions do not deposit onto the carbon support.

[00177] It is currently believed that at least a portion of the coordinating solvent is present on the carbon support at the outset of treatment of the precursor composition. Thus, the boiling point of the coordinating solvent may affect the ability of solvent molecules on the surface of the carbon support to promote an advantageous particle size distribution. That is, if all solvent molecules are removed from the carbon support at or near the outset of heating of the precursor composition, aggregation of metal particles to form relatively large metal particles may proceed in preference to formation of the transition metal composition. Thus, it is generally preferred for the boiling point of the solvent to be such that solvent molecules remain on the surface of the carbon support during at least a portion of the period of heating the precursor composition and thereby inhibit aggregation of metal particles during formation of the transition metal composition. Generally, the boiling point of the coordinating solvent is at least 100⁰C, at least about 150⁰C, at least about 200°C, or at least about 250⁰C.

[00178] Generally, the coordinating solvent utilized in the process of the present invention comprises an amine, an ether (e.g., a crown ether, glycol ether) or a salt thereof, an alcohol, an amino acid or a salt thereof, a hydroxyacid, or a combination thereof.

[00179] In various embodiments, the coordinating solvent comprises an amine selected from the group consisting of ethylenediamine, tetramethylenediamine, hexamethylenediamine, N, N, N ' , N ' , N ' ' pentamethyldiethylenetriamine, and combinations thereof .

[00180] In other embodiments, the coordinating solvent comprises an ether such as, for example, crown ethers, glycol ethers, and combinations thereof. In particular, the coordinating solvent may comprise a glycol ether such as glyme, ethyl glyme, triglyme, tetraglyme, polyglyme, diglyme, ethyl diglyme, butyl diglyme, diethylene glycol diethyl ether (i.e., ethyl diglyme) , dipropylene glycol methyl ether, diethylene glycol ethyl ether acetate, and combinations thereof. The coordinating solvent may also comprise a crown ether such as 1, 4, 7, 10-tetraoxacyclododecane (12-crown-4 ) , 1,4,7,10,13,16- hexaoxacyclooctadecane (18-crown-6) , or a combination thereof. In still other embodiments, the coordinating solvent may comprise an alcohol or polyol, such as polyethylene glycol, polypropylene glycol, and combinations thereof.

[00181] In still further embodiments, the liquid medium contacting the carbon may include a coordinating agent such as an amino acid or a salt thereof. In particular, the coordinating agent may typically comprise iminodiacetic acid, a salt of iminodiacetic acid, N- (phosphonomethyl) iminodiacetic acid, a salt of N- (phosphonomethyl) iminodiacetic acid, ethylenediaminetetraacetic acid (EDTA) , or a combination thereof.

[00182] In other such embodiments, the coordinating agent may comprise a hydroxyacid such as oxalic acid, citric acid, lactic acid, malic acid, and combinations thereof.

[00183] In certain embodiments, the coordinating solvent may be selected in view of the source of transition metal. For example, in the case of a transition metal composition comprising cobalt, use of a source of transition metal comprising cobalt nitrate along with a coordinating solvent comprising diglyme has produced active catalysts, though it will be understood that other coordinating solvents can be used with cobalt nitrate, and multiple other combinations of cobalt salt and coordinating solvent can be used.

Solvents Less Polar Than Water and Low Surface Tension

Solvents

[00184] Other solvents may constitute or be incorporated in a mixture or liquid medium that contacts the carbon support for deposition of the precursor composition. At least certain of these other solvents are believed to provide a relatively sparse dispersion of metal ions on the basis of a greater affinity than water for wetting the carbon surface. This affinity of the solvent for the carbon surface is currently believed to conduce to distribution and deposition of solvated metal ions over a greater portion of the carbon surface than observed with water- solvated metal ions.

[00185] Since the surface of the carbon support is generally non-polar (though limited polarity may be imparted by atmospheric oxidation of the carbon surface, or oxidation incident to precursor deposition) , solvents that have a polarity less than water are believed to more effectively wet the surface of the carbon support than water, due to the reduced difference in polarity between the solvent and support. One measure of the polarity of a liquid is its dielectric constant. Water generally exhibits a dielectric constant of approximately 80 (at 20⁰C) . Thus, solvents suitable for use in accordance with the present invention typically exhibit a dielectric constant (at 20⁰C) of less than 80, less than about 70, less than about 60, less than about 50, or less than about 40. However, solvents that are less polar than water to such a degree that the affinity of the solvent for wetting the carbon surface predominates over its ability to provide a relatively sparse dispersion of metal ions over the surface of the carbon support are undesired. Thus, the solvent preferably exhibits a certain minimum threshold of polarity. Accordingly, solvents suitable for use in the present invention typically exhibit a dielectric constant (at 20⁰C) of at least about 2, at least about 5, at least about 10, at least about 20, or at least about 30 and up to any one of the previously stated maxima. Thus, solvents used in the present invention typically exhibit a dielectric constant (at 20⁰C) of from about 2 to less than 80, more typically from about 5 to about 70, still more typically from about 10 to about 60, and, even more typically, from about 20 to about 50 or from about 30 to about 40. Depending on, for example, the solvent and the desired characteristics of the finished catalyst, in various embodiments the solvent may exhibit a dielectric constant near the lower or upper bounds of these generally broad ranges. Accordingly, in various embodiments, the solvent typically exhibits a dielectric constant (at 20⁰C) of from about 5 to about 40, more typically from about 10 to about 30 and, still more typically, from about 15 to about 25. In various other embodiments, the solvent typically exhibits a dielectric constant (at 20⁰C) of from about 40 to less than 80, more typically from about 50 to about 70 and, still more typically, from about 55 to about 65.

[00186] Additionally or alternatively, the affinity of a solvent for wetting the carbon surface may also be expressed in terms of the interfacial tension between the carbon support and the solvent; that is, the lower the interfacial tension between the solvent and carbon support surface the greater the effectiveness of the solvent for wetting the carbon surface. The surface tension of a solvent is generally proportional to the interfacial tension it will provide with a surface. Thus, the affinity of a solvent for wetting the carbon surface may also be expressed in terms of the solvent's surface tension; that is, a solvent having a surface tension less than that of water is believed to more effectively wet the carbon surface than water. Water typically exhibits a surface tension (at 20⁰C) of 70 dynes/cm. Solvents for use in accordance with the present invention on the basis of their affinity for wetting the carbon surface exhibit a surface tension of less than 70 dynes/cm, typically less than about 60 dynes/cm, less than about 50 dynes/cm, or less than about 40 dynes/cm. However, as with polarity, a minimum threshold of surface tension is preferred so that the affinity of the solvent for wetting the carbon surface does not predominate over its ability to provide solvated metal ions to a degree that substantially impedes precursor composition formation. Accordingly, solvents suitable for use in the present invention typically exhibit a surface tension (at 20⁰C) of at least about 2 dynes/cm, at least about 5 dynes/cm, at least about 10 dynes/cm, at least about 15 dynes/cm, or at least about 20 dynes/cm and up to one of the previously stated maxima. In various embodiments the solvent exhibits a surface tension near the lower or upper bounds of these generally broad ranges. Accordingly, in various embodiments, the solvent typically exhibits a surface tension (at 20⁰C) of from about 5 to about 40 dynes/cm, more typically from about 10 to about 30 dynes/cm and, still more typically, from about 15 to about 25 dynes/cm. In various other embodiments, the solvent exhibits a surface tension (at 20⁰C) of from about 40 to less than 70 dynes/cm and, more typically, from about 50 to about 60 dynes/cm.

[00187] Coordinating solvents also may contribute to advantageous (i.e., relatively sparse) dispersion of metal ions or coordinated metal salt ions due to affinity of the solvent for the carbon surface, effectively wetting the surface. Coordinating (e.g., chelating) solvents generally exhibit both non-polar and polar characteristics; non-polar portions bond to the non-polar carbon support and polar portions bond to the polar metal. Non-polar portions of the solvent are less polar than water; thus, the difference in polarity between the support and solvent is less than that between the support and water, so that the solvent is more likely to wet the surface of the carbon support .

[00188] Although there is a general preference for solvents that meet the dielectric constant and/or surface tension parameters outlined above, certain relatively more polar solvents such as dimethyl sulfoxide or dimethyl formamide are also considered to be suitable for use in depositing a precursor composition onto a carbon support. In commercial implementation of the processes of the invention for preparation of catalysts of the invention, those skilled in the art may choose to consider any of a variety of readily available solvents, some of which are strongly co-ordinating, such as glyme, diglyme, tetraglyme, polyglyme, etc., some of which are moderately polar but not typically classified as strongly co-ordinating, such as methanol, ethanol, propanol, butanol, ethylene glycol, propylene glycol, acetic acid, lactic acid, gluconic acid, diethyl ether, ethylene carbonate, and others of which are considered rather strongly polar, such as dimethyl sulfoxide or dimethyl formamide. Various combinations of such solvents may conveniently be used to tailor the properties of the solvent for optimum dispersion of the precursor composition on the carbon support .

[00189] In various embodiments, inclusion of a solvent may have a greater effect on the size of discrete particles formed on the support than selection of the metal salt. Thus, selection of a "bulky" salt in accordance with the preceding discussion is not required to achieve advantageous precursor composition dispersion where the salt is deposited from a mixture or liquid medium comprising a solvent which effectively promotes dispersion. However, in various preferred embodiments, a transition metal salt selected in accordance with the preceding discussion is incorporated into an aqueous medium comprising a solvent.

[00190] The carbon support may be contacted with the source compound and a liquid medium comprising a coordinating solvent, non-polar solvent, and/or low surface tension solvent either concurrently or sequentially.

[00191] Preferably, the carbon support is concurrently contacted with the source compound and solvent (s), and is typically contacted with the source compound in a liquid medium comprising the source compound dissolved or dispersed in solvent (s). Preferably, the carbon support is contacted with a mixture comprising the transition metal source and a liquid medium comprising a coordinating, non-polar, and/or low surface tension solvent. Optionally, such medium may also be aqueous.

[00192] In the case of sequential contact of the carbon support with the source compound and solvent (s), the order of contact is not critical. In various such embodiments, the carbon support is first contacted with the source compound and then contacted with a liquid medium comprising the solvent (s) . In other embodiments the carbon support is first contacted with a liquid medium comprising the solvent (s) followed by contact with the source compound.

[00193] In accordance with any of the embodiments described above, the liquid medium may be aqueous. In still other embodiments, the liquid medium may consist essentially of a coordinating solvent, non-polar solvent, low surface tension solvent, or a combination thereof.

[00194] Preferably the liquid medium comprises at least about 5 wt .% of polar organic solvent (s) that have a polarity and/or surface tension less than water or that provide a lower interfacial tension between the solvent and the carbon support than between water and the support. More preferably, the liquid medium comprises at least about 15 wt.%, at least about 25 wt.%, at least about 35 wt.%, at least 45 wt.%, at least 55 wt.% of such polar organic solvent (s), at least about 70 wt.%, at least about 80 wt.% or at least about 90 wt.% of such as solvent (s) . Typically, the polar organic solvent (s) may constitute between about 5% to about 95%, more typically between about 15% and about 85%, still more typically between about 25% and about 75%, even more typically from about 35% to about 65%, an in many cases between about 45% and about 55%, by weight polar organic solvent. The fraction of the liquid medium constituted by polar solvents can be constituted either entirely of coordinating solvent (s), by a mixture of coordinating solvent and another polar organic solvent, or entirely of such other organic solvent. In the embodiments wherein the non-aqueous solvent component is exclusively constituted of coordinating solvent (s), the above stated preferences for minimum polar organic solvent content and ranges of polar organic solvent content apply to the chelating or other coordinating solvent, and where the nonaqueous solvent is exclusively constituted of other polar organic solvent (s), such as, for example, lower primary alcohol (s), the above stated minimums and ranges apply to such other polar organic solvent (s).

[00195] It should further be understood that the liquid medium can contain some fraction, ordinarily a minor fraction of a non-polar solvent such as, e.g., hexane, heptane, octane or decane. Such non-polar solvents might be used to adjust the surface tension or dielectric constant of the liquid medium, or to adjust the interfacial tension between the liquid medium and the carbon support. In such case the above stated preferences for minimum and ranges of organic solvent content apply to the sum of all organic solvents, polar and non-polar.

[00196] Consistently with the above stated preferred minimums and ranges, the weight ratio of polar organic solvent or mixture of polar organic solvents to water is generally at least about 0.05:1, at least about 0.5:1, at least about 1:1, at least about 5:1, or at least about 10:1. Typically, the weight ratio of a solvent or mixture of polar organic solvent (s) to water in such embodiments is from about 0.05:1 to about 15:1, more typically from about 0.5:1 to about 10:1 and, still more typically, from about 1:1 to about 5:1.

Vapor Deposition

[00197] A source compound or derivative may also be formed on the carbon support by vapor deposition methods in which the carbon support is contacted with a mixture comprising a vapor phase source of a transition metal or secondary metallic element. In chemical vapor deposition the carbon support is contacted with a volatile metallic compound generally selected from the group consisting of halides, carbonyls, and organometallic compounds which decomposes to produce a transition metal suitable for formation on the carbon support. Examples of suitable metal carbonyl compounds include Mo(CO)₆, W(CO)₆, Fe(CO)₅, and Co(CO)₄.

[00198] Decomposition of the compound generally occurs by subjecting the compound to light or heat. In the case of decomposition using heat, temperatures of at least about 100⁰C are typically required for the decomposition.

[00199] It should be understood that the precursor compound formed on the carbon support and heated to form a transition metal composition may be the same as the source compound, or it may differ as a result of chemical transformation occurring during the process of deposition and/or otherwise prior to contact with a nitrogen-containing compound, carbon-containing compound (e.g., a hydrocarbon), nitrogen and carbon-containing compound, and/or a non-oxidizing atmosphere. For example, where a porous carbon support is impregnated with an aqueous solution of a source compound comprising ammonium molybdate, the precursor is ordinarily the same as the source compound. But where vapor deposition techniques are used with a source compound such as a molybdenum halide, the precursor formed may be metallic molybdenum or molybdenum oxide.

2. Heat Treatment of the Carbon Support

[00200] Regardless of the method for formation of the source compound or its derivative (e.g., precursor of a transition metal composition) on the carbon support, in certain embodiments the pretreated support is then subjected to further treatment (e.g., temperature programmed treatment) to form a transition metal composition or compositions comprising a transition metal and nitrogen, a transition metal and carbon, or a transition metal, nitrogen, and carbon on or over the surface of the carbon support. Generally, the pretreated carbon support is contacted with a nitrogen-containing, carbon-containing, or nitrogen and carbon-containing compound under certain, ordinarily relatively severe, conditions (e.g., elevated temperature). Generally, a fixed or fluidized bed comprising carbon support having the precursor deposited and/or formed thereon is contacted with a nitrogen- and/or carbon-containing compound. Preferably, the carbon support is established in a fixed bed reactor and a vapor-phase nitrogen-containing, carbon-containing, or nitrogen and carbon-containing compound is contacted with the support by passage over and/or through the bed of carbon support.

[00201] In the case of transition metal catalysts comprising a composition comprising a primary transition metal composition and a secondary metallic element, a composition comprising both precursor compositions may be formed on the carbon support followed by treatment at elevated temperatures. Precursor compositions can be formed concurrently or sequentially in accordance with the preceding discussion. Such a method for preparing a catalyst comprising two transition metal compositions utilizing a single treatment at elevated temperatures is hereinafter referred to as the "one step" method. Alternatively, catalysts comprising more than one transition metal composition, or a transition metal and a secondary metallic element, can be prepared by forming a single precursor on the carbon support, treating the support and precursor at elevated temperatures to produce a transition metal composition, forming a second precursor over the carbon support, and treating the support having the second precursor thereover at elevated temperatures. Such a method for preparing a catalyst comprising two transition metal compositions, or a primary transition metal composition and a secondary catalytic composition, utilizing two treatments at elevated temperatures is hereinafter referred to as the "two step" method.

[00202] In various embodiments when a transition metal composition (s) comprising a transition metal and nitrogen is (are) desired, typically the pretreated carbon support is contacted with any of a variety of nitrogen-containing compounds which may include ammonia, an amine, a nitrile, a nitrogen- containing heterocyclic compound, or combinations thereof. Exemplary nitrogen-containing compounds useful for this purpose include ammonia, dimethylamine, ethylenediamine, isopropylamine, butylamine, melamine, acetonitrile, propionitrile, picolonitrile, pyridine, pyrrole, and combinations thereof.

[00203] Typically, the carbon support having at least one precursor of a transition metal composition formed or deposited thereon is contacted with a nitriding atmosphere which comprises a vapor phase nitrogen-containing compound as set forth above. In a preferred embodiment, the nitrogen-containing compound comprises acetonitrile. Typically, the nitriding atmosphere comprises at least about 5% by volume of nitrogen-containing compound and, more typically, from about 5 to about 20% by volume of the nitrogen-containing compound. Generally, the carbon support is contacted with at least about 100 liters of nitrogen-containing compound per kg of carbon per hour (at least about 3.50 ft³ of nitrogen-containing compound per Ib of carbon per hour) . Preferably, the carbon support is contacted with from about 200 to about 500 liters of nitrogen-containing compound per kg of carbon per hour (from about 7.0 to about 17.7 ft³ of nitrogen-containing compound per Ib of carbon per hour) .

[00204] The nitriding atmosphere optionally includes additional components selected from the group consisting of hydrogen and inert gases such as argon. Hydrogen, where present, generally may be present in a proportion of at least about 1% by volume hydrogen or, more generally, from about 1 to about 10% by volume hydrogen. Additionally or alternatively, the nitriding atmosphere typically comprises at least about 75% by volume argon and, more typically, from about 75 to about 95% by volume argon or other inert gas. In certain embodiments, the nitriding atmosphere comprises at least about 10 liters of hydrogen per kg of carbon support per hour (at least about 0.35 ft³ of hydrogen per Ib of carbon support) . Preferably, such a nitriding atmosphere comprises from about 30 to about 50 liters of hydrogen per kg of carbon support per hour (from about 1.05 to about 1.8 ft³ of hydrogen per Ib of carbon support per hour) . In various other embodiments, the nitriding atmosphere comprises at least about 900 liters of argon or other inert gas per kg of carbon support per hour (at least about 31.5 ft³ of argon per Ib of carbon support) . Preferably, such a nitriding atmosphere comprises from about 1800 to about 4500 liters of argon per kg of carbon support per hour (from about 63 to about 160 ft³ of argon per Ib of carbon support per hour) . In further embodiments, the nitriding atmosphere comprises at least about 10 liters of hydrogen per kg of carbon support per hour (at least about 0.35 ft³ of hydrogen per Ib of carbon support) and at least about 900 liters of argon per kg of carbon support per hour (at least about 31.5 ft³ of argon per Ib of carbon support) .

[00205] The carbon support having at least one precursor of a transition metal composition thereon is typically contacted with the nitrogen-containing compound in a nitride reaction zone under a total pressure of no greater than about 15 psig. Typically, the nitride reaction zone is under a pressure of from about 2 to about 15 psig. The nitrogen-containing compound partial pressure of the nitride reaction zone is typically no greater than about 2 psig and, more typically, from about 1 to about 2 psig. The partial pressure of any hydrogen present in the nitriding zone is typically less than about 1 psig and, more typically, from about 0.1 to about 1 psig. However, if equipment constructed of high temperature alloys is used for contacting the carbon support with a nitrogen-containing compound, higher pressures may be employed.

[00206] When a transition metal composition comprising a transition metal and carbon is desired, typically the pretreated carbon support is contacted with a carbiding atmosphere containing a carbon-containing compound including, for example, hydrocarbons such as methane, ethane, propane, butane, and pentane .

[00207] In certain embodiments, the pretreated carbon support, having a precursor transition metal compound thereon, may be treated to form a transition metal composition comprising both carbon and nitrogen and the transition metal on the carbon support. In such embodiments, the precursor compound on the support may be contacted with a "carbiding-nitriding atmosphere." One method involves contacting the pretreated carbon support with a carbon and nitrogen-containing compound. Suitable carbon and nitrogen-containing compounds include amines, nitriles, nitrogen-containing heterocyclic compounds, or combinations thereof. Such carbon and nitrogen-containing compounds are generally selected from the group consisting of dimethylamine, ethylenediamine, isopropylamine, butylamine, melamine, acetonitrile, propionitrile, picolonitrile, pyridine, pyrrole, and combinations thereof.

[00208] Typically, the carbon support having a precursor of the transition metal composition deposited or formed thereon is contacted with a carbiding-nitriding atmosphere which comprises a vapor phase carbon and nitrogen-containing compound. Typically, the carbiding-nitriding atmosphere comprises at least about 5% by volume of carbon and nitrogen-containing compound and, more typically, from about 5 to about 20% by volume of the carbon and nitrogen-containing compound. Generally, at least about 100 liters of carbon and nitrogen-containing compound per kg of carbon per hour (at least about 3.50 ft³ of carbon and nitrogen-containing compound per Ib of carbon per hour) are contacted with the carbon support. Preferably, from about 200 to about 500 liters of carbon and nitrogen-containing compound per kg of carbon per hour (from about 7.0 to about 17.7 ft³ of carbon and nitrogen-containing compound per Ib of carbon per hour) are contacted with the carbon support.

[00209] The carbiding-nitriding atmosphere optionally includes additional components selected from the group consisting of hydrogen and inert gases such as argon. Hydrogen, where present, is generally present in a proportion of at least about 1% by volume or, more generally, from about 1 to about 5% by volume. In certain embodiments, the carbiding-nitriding atmosphere comprises at least about 10 liters of hydrogen per kg of carbon support per hour (at least about 0.35 ft³ of hydrogen per Ib of carbon support) . Preferably, such a carbiding- nitriding atmosphere comprises from about 30 to about 50 liters of hydrogen per kg of carbon support per hour (from about 1.05 to about 1.8 ft³ of hydrogen per Ib of carbon support per hour) . [00210] In various other embodiments, the carbiding- nitriding atmosphere comprises at least about 900 liters of argon per kg of carbon support per hour (at least about 31.5 ft³ of argon per Ib of carbon support) . Preferably, such a carbiding-nitriding atmosphere comprises from about 1800 to about 4500 liters of argon per kg of carbon support per hour (from about 63 to about 160 ft³ of argon per Ib of carbon support per hour) .

[00211] In further embodiments, the carbiding-nitriding atmosphere comprises at least about 10 liters of hydrogen per kg of carbon support per hour (at least about 0.35 ft³ of hydrogen per Ib of carbon support) and at least about 900 liters of argon per kg of carbon support per hour (at least about 31.5 ft³ of argon per Ib of carbon support) .

[00212] The carbon support having a precursor of the transition metal composition thereon is typically contacted with the carbon and nitrogen-containing compound in a carbide-nitride reaction zone under a total pressure of no greater than about 15 psig. Typically, the carbide-nitride reaction zone is under a pressure of from about 2 to about 15 psig. The carbon and nitrogen-containing compound partial pressure of the carbide- nitride reaction zone is typically no greater than about 2 psig and, more typically, from about 1 to about 2 psig. The partial pressure of any hydrogen present in the carbide-nitride reaction zone is typically less than about 1 psig and, more typically, from about 0.1 to about 1 psig. As with nitriding and carbiding atmospheres, if equipment constructed of high temperature alloys is used for contacting the carbon support with a carbon and nitrogen-containing compound, higher pressures may be employed.

[00213] Additionally or alternatively, a transition metal composition comprising a transition metal, carbon, and nitrogen may be formed by contacting the support and precursor with a nitrogen-containing compound as described above with the carbon of the transition metal composition derived from the supporting structure .

[00214] In further embodiments, the support and precursor of the transition metal composition may be contacted with a nitrogen-containing compound (e.g., ammonia) and a carbon- containing compound (e.g., methane) as set forth above to form a transition metal composition comprising a transition metal, carbon, and nitrogen on and/or over the carbon support.

[00215] In still further embodiments the carbon support is contacted with a compound comprising a transition metal, nitrogen, and carbon to form a precursor of the transition metal composition thereon (i.e., the source compound and carbon and nitrogen-containing compound are provided by one composition) and heated in accordance with the following description to form a transition metal composition comprising a transition metal, nitrogen, and carbon on a carbon support. Typically, such compositions comprise a co-ordination complex comprising nitrogen-containing organic ligands including, for example, nitrogen-containing organic ligands including five or six membered heterocyclic rings comprising nitrogen. Generally, such ligands are selected from the group consisting of porphyrins, porphyrin derivatives, polyacrylonitrile, phthalocyanines, pyrrole, substituted pyrroles, polypyrroles, pyridine, substituted pyridines, bipyridyls, phthalocyanines, imidazole, substituted imidazoles, pyrimidine, substituted pyrimidines, acetonitrile, o-phenylenediamines, bipyridines, salen ligands, p-phenylenediamines, cyclams, and combinations thereof. In certain embodiments, the co-ordination complex comprises phthalocyanine (e.g., a transition metal phthalocyanine) or a phthalocyanine derivative. Certain of these co-ordination complexes are also described in Coleman et al. International Publication No. WO 03/068387 Al and U.S. Patent No. 7,129,373 to Coleman et al . , the entire disclosure of which is hereby incorporated by reference.

[00216] To deposit and/or form the transition metal composition precursor in such embodiments, typically a suspension is prepared comprising the carbon support and the coordination complex which is agitated for a time sufficient for adsorption of the co-ordination compound on the carbon support. Typically, the suspension contains the carbon support in a proportion of from about 5 to about 20 g/liter and the coordination compound in a proportion of from about 2 to about 5. Preferably, the carbon support and co-ordination compound are present in a weight ratio of from about 2 to about 5 and, more preferably, from about 3 to about 4.

[00217] Formation of a transition metal composition on the carbon support proceeds by heating the support and precursor in the presence of an atmosphere described above (i.e., in the presence of a nitrogen-containing, carbon-containing, or nitrogen and carbon-containing compound) . Typically, the carbon support having the precursor thereon is heated using any of a variety of means known in the art including, for example, an electrical resistance furnace or an induction furnace.

[00218] Generally, the transition metal composition precursor may contain a transition metal salt, partially hydrolyzed transition metal, and/or a transition metal oxide. For example, in the case of iron, the precursor may comprise FeCl₃, Fe(OH)₃, Fe(OH)₂ ⁺¹, Fe(OH)⁺², and/or Fe₂O₃. Generally, heating the carbon support having a precursor of the transition metal composition thereon forms the transition metal composition by providing the energy necessary to replace the bond between the transition metal and the other component of the precursor composition (s) with a bond between the transition metal and nitrogen, carbon, or carbon and nitrogen. Additionally or alternatively, the transition metal composition may be formed by reduction of transition metal oxide to transition metal which combines with the carbon and/or nitrogen of the composition present in the nitriding, carbiding, or carbiding-nitriding atmosphere with which the carbon support is contacted to form the transition metal composition.

[00219] Typically, the support (i.e., carbon support having a precursor of a transition metal composition thereon) is heated to a temperature of at least about 600⁰C, more typically to a temperature of at least about 700⁰C, still more typically to a temperature of at least about 800⁰C and, even more typically, to a temperature of at least about 850⁰C to produce the transition metal composition.

[00220] The maximum temperature to which the support is heated is generally sufficient to produce a transition metal nitride, transition metal carbide, or transition metal carbide- nitride. The support can be heated to temperatures greater than 1000°C, greater than 1250°C, or up to about 1500°C. It has been observed, however, that graphitization of the carbon support may occur if the support is heated to temperatures above 1000⁰C or above 1100⁰C. Graphitization may have a detrimental effect on the activity of the catalyst. Thus, preferably, the support is heated to a temperature of no greater than about 1000⁰C. However, active catalysts can be prepared by heating the support and precursor to temperatures in excess of 1000⁰C, regardless of any graphitization which may occur. Preferably, the support is heated to a temperature of from about 600⁰C to about 1000⁰C, more preferably, from about 600 to about 975°C, more preferably from about 700 to about 975°C, even more preferably from about 800 to about 975°C, still more preferably from about 850 to about 975°C and especially to a temperature of from about 850⁰C to about 950°C. [00221] In the case of a carbiding atmosphere comprising a hydrocarbon (e.g., methane), it has been observed that heating the carbon support to temperatures above 700⁰C may cause polymeric carbon to form on the carbon support. Thus, in certain embodiments in which a transition metal composition comprising a transition metal and carbon is desired, it may be preferable to form such a composition by heating the support to temperatures of from about 600 to about 700⁰C. However, it should be understood that formation of a transition metal composition comprising a transition metal and carbon proceeds at temperatures above 700⁰C and such a method produces suitable catalysts for use in accordance with the present invention provided T_max is sufficient for carbide formation (e.g., at least 500°C or at least 600°C) .

[00222] The rate of heating is not narrowly critical. Typically, the support having a precursor deposited or formed thereon is heated at a rate of at least about 2°C/minute, more typically at least about 5°C/minute, still more typically at least about 10°C/minute and, even more typically, at a rate of at least about 12°C/minute. Generally, the support having a precursor thereon is heated at a rate of from about 2 to about 15°C/minute and, more generally, at a rate of from about 5 to about 15°C/minute.

[00223] Likewise, the time at which the catalyst is maintained at the maximum temperature (i.e., the holding time) is not narrowly critical. Typically, the catalyst is maintained at the maximum temperature for at least about 30 minutes, more typically at least about 1 hour and, still more typically, from about 1 to about 3 hours. In various embodiments, the catalyst is maintained at the maximum temperature for about 2 hours.

[00224] Typically, the transition metal catalyst is prepared in a batch process (e.g., in a fluid or fixed bed reaction chamber) over a cycle time (i.e., the period of time which includes heating the support and precursor to its maximum temperature and maintaining at the maximum temperature) of at least about 1 hour, more typically at least about 2 hours and, still more typically, at least about 3 hours. In various embodiments, the cycle time for catalyst preparation is about 4 hours .

[00225] Transition metal catalyst may also be prepared by heating the support and precursor in a continuous fashion using, for example, a kiln through which a heat treatment atmosphere is passed. Various types of kilns may be used including, for example, rotary kilns and tunnel kilns. Typically, the residence time of the catalyst in the kiln is at least about 30 minutes, more typically at least about 1 hour and, still more typically, at least about 2 hours. In various such embodiments, the residence time of the catalyst in the kiln is from about 1 to about 3 hours and, in others, the residence time of the catalyst in the kiln is from about 2 to about 3 hours.

[00226] Another method includes contacting a volatile metal compound and a carbon support at temperatures ranging from about 500 to about 1400⁰C to reduce the volatile metal compound which then reacts with the carbon support to form a carbide. The volatile metal compound is generally an organometallic compound.

[00227] In the transition metal/nitrogen composition, or transition metal/nitrogen/carbon composition, it is believed that the transition metal is bonded to nitrogen atoms by coordination bonds. In at least certain embodiments of the process for preparing the catalyst, a nitrogen-containing compound may be reacted with the carbon substrate, and the product of this reaction further reacted with a transition metal source compound or precursor compound to produce a transition metal composition in which the metal is co-ordinated to the nitrogen. Reaction of the nitrogen-containing compound with the carbon substrate is believed to be incident to many if not most embodiments of the process for preparing the transition metal composition, but can be assured by initially contacting a carbon substrate with the nitrogen-containing compound under pyrolysis conditions in the absence of the transition metal or source thereof, and thereafter cooling the pyrolyzed nitrogen- containing carbon, impregnating the cooled nitrogen-containing carbon with a transition metal precursor compound, and pyrolyzing again. According to this alternative process, during the first pyrolysis step the carbon may be contacted with a nitrogen-containing gas such as ammonia or acetonitrile at greater than 700⁰C, typically about 900⁰C. The second pyrolysis step may be conducted in the presence of an inert or reducing gas (e.g., hydrogen and/or additional nitrogen-containing compound) under the temperature conditions described herein for preparation of a transition metal/nitrogen composition or transition metal/nitrogen/carbon composition on a carbon support. Conveniently, both pyrolysis steps may be conducted by passing a gas of appropriate composition through a fixed or fluid bed comprising a particulate carbon substrate.

[00228] Where nitrogen is combined with the carbon substrate, the nitrogen atoms on the carbon support are understood to be typically of the pyridinic-type wherein nitrogen contributes one π electron to carbon of the support, e.g., to the graphene plane of the carbon, leaving an unshared electron pair for co-ordination to the transition metal. It is further preferred that the concentration of transition metal on the support be not substantially greater than that required to saturate the nitrogen atom co-ordination sites on the carbon. Increasing the transition metal concentration beyond that level may result in the formation of zero valence (metallic form) of the transition metal, which is believed to be catalytically inactive for at least certain reactions. The formation of zero valence transition metal particles on the surface may also induce graphitization around the metal particles. Although the graphite may itself possess catalytic activity for certain reactions, graphitization reduces effective surface area, an effect that, if excessive, may compromise the activity of the transition metal catalyst.

[00229] In various embodiments, a secondary metallic element is deposited on or over a carbon support having a primary transition metal composition formed thereon using a variation of the "two step" method described above. In this variation, the second treatment is not necessarily performed in the presence of a nitrogen-containing compound and/or nitrogen and carbon- containing compound but, rather, is carried out in the presence of a non-oxidizing environment which generally consists essentially of inert gases such as N₂, noble gases (e.g., argon, helium) or mixtures thereof. In certain embodiments the secondary metallic element in elemental or metallic form is deposited on or over the surface of the carbon support and/or on or over the surface of a primary transition metal composition (i.e., a secondary catalytic composition comprising nitrogen and/or carbon is not required) . In such embodiments, the non- oxidizing environment comprises a reducing environment and includes a gas-phase reducing agent, for example, hydrogen, carbon monoxide or combinations thereof. The concentration of hydrogen in a reducing environment may vary, although a hydrogen content of less than 1% by volume is less preferred when reduction of the catalyst surface is desired as such concentrations require a longer time to reduce the catalyst surface. Typically, hydrogen is present in the heat treatment atmosphere at a concentration of from about 1 to about 10% by volume and, more typically, from about 2 to about 5% by volume. The remainder of the gas may consist essentially of a non- oxidizing gas such as nitrogen, argon, or helium. Such non- oxidizing gases may be present in the reducing environment at a concentration of at least about 90% by volume, from about 90 to about 99% by volume, still more typically, from about 95 to about 98% by volume.

D . Transition Metal Catalyst Features

[00230] Generally, it is preferred for the transition metal catalysts of the present invention and the catalysts of catalyst combinations of the present invention to have a high surface area. Formation of a transition metal/nitrogen, transition metal/carbon and/or transition metal/carbon/nitrogen composition on a carbon support typically is associated with some reduction in Langmuir surface area. Loss of surface area may be a result of coating of the carbon surface with a transition metal composition of relatively lower surface area, e.g., in the form of an amorphous film and/or relatively large particles of the transition metal composition. Amorphous transition metal composition may be in the form of either amorphous particles or an amorphous film. Preferably, the sacrifice in surface area is not greater than about 40%. Where the transition metal composition is formed under the preferred conditions described above, the loss in total Langmuir surface area is typically between about 20 and about 40%. Thus, generally, the surface area of a catalyst (i.e., carbon support having one or more transition metal compositions formed thereon) is at least about 60% of the surface area of the carbon support prior to formation of the transition metal composition (s) thereon and, more generally, from about 60 to about 80%. In various embodiments, the surface area of a catalyst is at least about 75% of the surface area of the carbon support prior to formation of the transition metal composition (s) thereon.

[00231] Typically, the transition metal catalyst has a total Langmuir surface area of at least about 500 m²/g, more typically at least about 600 m²/g. Preferably, the total Langmuir surface area of the catalyst is at least about 800 m²/g, more preferably at least about 900 m²/g. It is generally preferred that the total Langmuir surface area of the catalyst remains at a value of at least about 1000 m²/g, more preferably at least about 1100 m²/g, even more preferably at least about 1200 m²/g, after a transition metal composition has been formed on a carbon support. Generally, the catalyst has a total Langmuir surface area of less than about 2000 m²/g, from about 600 to about 1500 m²/g, typically from about 600 to about 1400 m²/g. In certain embodiments, the catalyst has a total Langmuir surface area of from about 800 to about 1200 m²/g. Preferably, the catalyst has a total Langmuir surface area of from about 1000 to about 1400 m²/g, more preferably from about 1100 to about 1400 m²/g and, even more preferably, from about 1200 to about 1400 m²/g.

[00232] The Langmuir surface area of a transition metal catalyst of the present invention attributed to pores having a diameter of less than 20 A (i.e., micropores) is typically at least about 750 m²/g, more typically at least 800 m²/g, still more typically at least about 800 m²/g and, even more typically, at least about 900 m²/g. Preferably, the micropore Langmuir surface area of the catalyst is from about 750 to about 1100 m²/g and, more preferably, from about 750 to about 1000 m²/g.

[00233] The Langmuir surface area of a transition metal catalyst of the present invention attributed to pores having a diameter of from about 20-40 A (i.e., mesopores) and pores having a diameter greater than 40 A (i.e., macropores) is generally at least about 175 m²/g and, more generally, at least about 200 m²/g. Preferably, the combined mesopore and macropore Langmuir surface area of the catalyst is from about 175 to about 300 m²/g and, more preferably, from about 200 to about 300 m²/g. In certain embodiments, the combined mesopore and macropore surface area is from about 175 to about 250 m²/g. [00234] Additionally or alternatively, it is preferred that the micropore Langmuir surface area of the transition metal catalyst remain at a value of at least about 750 m²/g, more preferably at least about 800 m²/g, and the combined mesopore and macropore Langmuir surface area of the catalyst remain at a value of at least about 175 m²/g, more preferably at least about 200 m²/g, after the transition metal composition has been formed.

[00235] It is further preferred that, as compared to the carbon support, the micropore Langmuir surface area be reduced by not more than 45%, more preferably not more than about 40%. Thus, the micropore Langmuir surface area of the transition metal catalyst is generally at least about 55% of the micropore Langmuir surface area of the carbon support prior to formation of the transition metal composition thereon, more generally at least about 60% or at least about 70%, and, still more generally, at least about 80%. Typically, the micropore Langmuir surface area of the catalyst is from about 55 to about 80% of the micropore Langmuir surface area of the carbon support prior to formation of the transition metal composition thereon, more typically from about 60 to about 80% and, still more typically, from about 70 to about 80%.

[00236] In addition to the preferred limitation on the extent to which the micropore surface area is reduced, it is further generally preferred that the combined mesopore and macropore Langmuir surface area be reduced by not more than about 30%, more preferably not more than about 20%, as a result of the formation of the transition metal composition on the carbon support. Thus, generally, the combined mesopore and macropore Langmuir surface area of the transition metal catalyst is generally at least about 70% of the combined mesopore and macropore Langmuir surface area of the carbon support prior to formation of the transition metal composition thereon and, more generally, at least about 80%. Typically, the combined mesopore and macropore Langmuir surface area of the catalyst is from about 70 to about 90% of the combined mesopore and macropore Langmuir surface area of the carbon support prior to formation of the transition metal composition thereon.

[00237] A further advantageous feature of the transition metal catalysts of the present invention is a pore volume sufficient to allow for diffusion of reactants into the pores of the catalyst. Thus, preferably, catalysts of the present invention including a transition metal composition formed on a carbon support typically have a pore volume of at least about 0.1 cm³/g, more typically at least about 0.3 cm³/g and, still more typically at least about 0.5 cm³/g. Generally, the catalyst has a pore volume of from about 0.1 to about 2 cm³/g, more generally from about 0.50 to about 2.0 cm³/g and, still more generally, from about 0.5 to about 1.5 cm³/g.

[00238] In addition to overall pore volume, the pore volume distribution of the transition metal catalysts of the present invention preferably conduces to diffusion of reactants into the pores of the finished catalyst. Preferably, pores having a diameter of less than about 20 A make up no more than about 45% of the overall pore volume of the catalyst and, more preferably, no more than about 30% of the overall pore volume. Pores having a diameter of greater than about 20 A preferably make up at least about 60% of the overall pore volume of the catalyst and, more preferably, at least about 65% of the overall pore volume.

[00239] It has been observed that "mesopores" (i.e., pores having a diameter of from about 20 to about 40 A) allow suitable diffusion of reactants into the pores of the catalyst. Thus, preferably mesopores make up at least about 25% of the overall pore volume and, more preferably, at least about 30% of the overall pore volume. Macropores (i.e., pores having a diameter larger than about 40 A) also allow suitable diffusion of reactants into the pores of the catalyst. Thus, preferably, these pores make up at least about 5% of the overall pore volume and, more preferably, at least about 10% of the overall pore volume of the catalyst.

[00240] In addition to overall pore volume, the pore volume distribution of these catalysts of the present invention preferably conduces to diffusion of reactants into the pores of the finished catalyst. Preferably, pores having a diameter of less than about 20 A make up no more than about 45% of the overall pore volume of the catalyst and, more preferably, no more than about 30% of the overall pore volume. Pores having a diameter of greater than about 20 A preferably make up at least about 60% of the overall pore volume of the catalyst and, more preferably, at least about 65% of the overall pore volume.

[00241] Generally, pore having a diameter greater than 20 A make up at least about 10% or from about 10% to about 405 of the total pore volume of the catalyst.

[00242] It has been observed that "mesopores" (i.e., pores having a diameter of from about 20 to about 40 A) allow suitable diffusion of reactants into the pores of a catalyst. Thus, preferably mesopores make up at least about 25% of the overall pore volume of these catalysts and, more preferably, at least about 30% of the overall pore volume. Macropores (i.e., pores having a diameter larger than about 40 A) also allow suitable diffusion of reactants into the pores of the catalyst. Thus, preferably, these pores make up at least about 5% of the overall pore volume and, more preferably, at least about 10% of the overall pore volume of the catalyst. Generally, such pore constitute from about 5% to about 20% of the total pore volume of the catalyst.

[00243] It is generally preferred for the transition metal composition (e.g., the transition metal carbide or transition metal nitride) to be distributed over the surface of the pores of the carbon particle (e.g., the surface of the pore walls and interstitial passages of the catalyst particles) . Thus, generally it is preferred that the transition metal composition be distributed over all surfaces accessible to fluid with which the catalyst is contacted. More particularly, it is preferred for the transition metal composition to be substantially uniformly distributed over the surface of the pores of the carbon particle.

[00244] Particle size of the transition metal composition, as determined, for example, by X-ray diffraction, affects such uniform distribution and it has been observed that the smaller the size of the particulate crystals of the transition metal composition, the more uniform its deposition. Where a transition metal composition is formed on a carbon support in accordance with a preferred method, in accordance with various embodiments, it is believed that the composition comprises a substantial fraction of very fine particles, e.g., wherein at least about 20 wt . % of the transition metal is in amorphous form or in the form of particles of less than 15 nm, more typically less than 5 nm, more typically 2 nm, as determined by X-ray diffraction .

[00245] In various particularly preferred embodiments of the invention, X-ray diffraction analysis at a detection limit of 1 nm does not detect any significant portion of transition metal composition particles. Thus, it is currently believed that the transition metal composition particles are present on the surface of the carbon support in the form of discrete particles having a particle size of less than 1 nm or are present on the surface of the carbon support in the form of an amorphous film. However, based on the decrease in surface area after formation of the transition metal composition on the carbon support, it is reasonable to infer the transition metal composition may be present at least in part as an amorphous film since an increase in surface area would be expected in the case of deposition of crystallites having a particle size below 1 nm.

[00246] In various embodiments of transition metal catalysts of the present invention, generally at least about 95% by weight of the transition metal composition particles formed on a carbon support have a particle size, in their largest dimension, of less than about 1000 nm. Typically, at least about 80% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 250 nm. More typically, at least about 70% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 200 nm. Still more typically, at least about 60% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 18 nm. Even more typically, at least about 20% by weight, preferably at least about 55% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 15 nm. Preferably, at least about 20% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 5 nm, more preferably, less than about 2 nm, and even more preferably, less than about 1 nm. More preferably, from about 20 to about 95% by weight of the transition metal composition particles have a particle size, in their largest dimension, of less than about 1 nm and, more preferably, from about 20 to about 100% by weight.

[00247] Generally, at least about 75%, on a number basis, of the transition metal composition particles have a particle size, in their largest dimension, of less than about 1000 nm. Typically, at least about 60%, on a number basis, of the transition metal composition particles have a particle size, in their largest dimension, of less than about 250 nm. More typically, at least about 50%, on a number basis, of the transition metal composition particles have a particle size, in their largest dimension, of less than about 200 nm. Still more typically, at least about 40%, on a number basis, of the transition metal composition particles have a particle size, in their largest dimension, of less than about 18 nm. Even more typically, at least about 35%, on a number basis, of the transition metal composition particles have a particle size, in their largest dimension, of less than about 15 nm.

[00248] It has been observed that uniform distribution of the transition metal composition on the carbon support (i.e., reduced clustering of the transition metal and/or suitable distribution of the transition metal composition throughout the pores of the carbon support) may improve catalytic activity of catalysts including a transition metal composition deposited on a carbon support and/or may allow for improved coating of a secondary metal or secondary transition metal composition on the carbon support having a transition metal composition formed on and/or over its surface.

[00249] Fig. 1 is a High Resolution Transmission Electron Microscopy (HRTEM) image of a carbon-supported molybdenum carbide prepared in accordance with the present invention in which molybdenum carbide is present in a proportion of 15% by weight. As shown, a carbon support having molybdenum carbide formed thereon prepared in accordance with the methods described above exhibits uniform dispersion of molybdenum carbide throughout the carbon support.

[00250] Fig. 2 is a Scanning Electron Microscopy (SEM) image of a carbon supported molybdenum carbide prepared in accordance with the present invention in which the carbide is present in a proportion of 10% by weight. As shown, a carbon support having molybdenum carbide formed thereon in a proportion of 10% by weight of the catalyst in accordance with the methods described above exhibits uniform distribution of molybdenum throughout the carbon support. Fig. 3 is a Transmission Electron Microscopy (TEM) image of a carbon supported molybdenum carbide prepared in accordance with the present invention in which the carbide is present in a proportion of 10% by weight. As shown, a carbon support having molybdenum carbide formed thereon in a proportion of 10% by weight of the catalyst in accordance with the above methods exhibits uniformity of molybdenum carbide distribution throughout believed to be due, at least in part, to the particle size distribution of molybdenum carbide.

[00251] Transition metal (M) , carbon and nitrogen containing ions corresponding to the formula MN_xC_y ⁺ are generated and detected when transition metal catalysts of the present invention (e.g., primary catalysts) are analyzed by Time-of- Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A in Example 24.

[00252] In various embodiments, the weighted molar average value of x (determined from the relative intensities of the various ion families detected by ToFSIMS analysis) is generally from about 0.5 to about 8.0, more generally from about 1.0 to about 8.0 and, still more generally, from about 0.5 to about 3.5. Typically, the weighted molar average value of x is from about 0.5 to about 3.0, from about 0.5 to about 2.6, from about 0.5 to about 2.2, from about 0.5 to about 2.1, or from about 0.5 to about 2.0. In various embodiments, the weighted molar average value of x is generally from 1.0 to about 8.0. Typically, the weighted molar average value of x is from 1.0 to about 5.0, more typically from 1.0 to about 3.0, more typically from 1.0 to about 2.10 and, still more typically, from about 1.0 to about 2.0 or from about 1.5 to about 2.0.

[00253] The weight molar average value of y is generally from about 0.5 to about 8.0 or from about 1.0 to about 8.0, more generally from about 0.5 to about 5.0 or from about 1.0 to about 5.0. In various embodiments, the weighted molar average value of y is from about 0.5 to about 2.6, more typically from 1.0 to about 2.6, still more typically from 1.5 to about 2.6 and, still more typically, from about 2.0 to about 2.6.

[00254] In particular, ions corresponding to the formula CoN_xCy⁺ are generated when cobalt-containing catalysts of the present invention are analyzed by ToF SIMS as described in Protocol A in Example 24. Generally, in such embodiments, the weighed molar average value of x is from about 0.5 to about 8.0 or from about 1.0 to about 8.0. Typically, the weighted molar average value of x is from about 0.5 to about 5.0 or from about 1.0 to about 5.0, more typically from about 0.5 to about 3.5, still more typically from about 0.5 to about 3.0 or from about 1.0 to about 3.0, even more typically from about 0.5 to about 2.2. The weighted molar average value of x in such embodiments may also typically be from 1.0 to about 2.1 and, more typically, from 1.0 to about 2.0 or from about 1.5 to about 2.0.

[00255] Further in accordance with embodiments in which the transition metal composition comprises cobalt, the weighted molar average value of y is generally from about 0.5 to about 8.0 or from about 1.0 to about 8.0. Typically, the weighted molar average value of y is from about 1.0 to about 5.0, more typically from 1.0 to about 4.0, still more typically from 1.0 to about 3.0 and, even more typically, from 1.0 to about 2.6 or from 1.0 to about 2.0.

[00256] It is believed that ions corresponding to the formula MN_xCy⁺ in which x is less than 4 provide a greater contribution to the activity of the catalyst than those ions in which x is 4 or greater. Additionally or alternatively, ions in which x is 4 or greater may detract from the activity of the catalyst. Thus, preferably, MN_xCy⁺ ions in which the weighted molar average value of x is from 4.0 to about 8.0 constitute no more than about 25 mole percent, more preferably no more than about 20 mole percent, still more preferably no more than about 15 mole percent, and, even more preferably, no more than about 10 mole percent of MN_xCy⁺ ions generated during the ToF SIMS analysis. The effect of ions of formulae in which x is greater than 4 is likewise observed in the case of ions corresponding to the formula CoN_xCy⁺. Thus, typically preferably CoN_xCy⁺ ions in which the weighted molar average value of x is from 4 to about 8 constitute no more than about 60 mole percent, more typically no more than about 50 mole percent and, still more typically, no more than about 40 mole percent of the CoN_xCy⁺ ions generated during ToF SIMS analysis. Preferably, CoN_xCy⁺ ions in which the weighted molar average value of x is from 4 to about 8 constitute no more than about 30 mole percent, more preferably no more than about 20 mole percent, still more preferably no more than about 15 mole percent and, even more preferably, no more than about 10 mole percent of the CoN_xC_y ⁺ ions generated during ToF SIMS analysis.

[00257] More particularly, it is believed that ions corresponding to the formula MN_xCy⁺ in which x is 1 provide a greater contribution to the activity of the catalyst than those ions in which x is 2 or greater. Thus, in various preferred embodiments, the relative abundance of ions in which x is 1 is typically at least about 20%, more typically at least about 25%, still more typically at least about 30%, even more typically at least about 35% and, even more typically, at least about 42% or at least about 45%. Further in accordance with such embodiments, ions corresponding to the formula MN_xCy⁺ in which x and y are each 1 may provide a greater contribution to the activity of the catalyst than those ions in which either x or y are 2 or greater. Thus, in accordance with certain embodiments, the relative abundance of MN_xCy⁺ ions in which both x and y are 1 may typically be at last about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, or at least about 35%. Further in accordance with such embodiments, the relative abundance of ions in which both x and y are 1 is generally from about 10% to about 40%, from about 15% to about 35%, or from about 20% to about 30%.

[00258] The total exposed metal surface area of catalysts of the present invention may be determined using static carbon monoxide chemisorption analysis, in particular, using the method described in Wan et al. International Publication No. WO 2006/031938, which includes first and second cycles. Transition metal catalysts of the present invention subjected to such analysis are characterized as chemisorbing less than about 2.5 μmoles of carbon monoxide per gram of catalyst, typically less than about 2 μmoles of carbon monoxide per gram of catalyst and, more typically, less than about 1 μmole during the second cycle which is indicative of the total exposed metal (e.g., Co) at the surface of the carbon support.

[00259] Exposed metal surface area (m² per gram catalyst) may be determined from the volume of CO chemisorbed using the following equation:

Metal surface area (m²/g catalyst) = 6.023*10²³ * V/2 * SF * A/22, 414, where:

V = volume of CO chemisorbed (cm³/g STP) (Volume of one mole of gas is 22,414 cm³ STP, i.e., the volume of one μmole of CO is 0.022414 cm³)

SF = stoichiometry factor (assumed to be equal to 1, i.e., one CO molecule per exposed metal atom)

A = effective area of one exposed metal atom (m²/atom) (8xlO^~20 m²/atom of metal)

[00260] Thus, transition metal catalysts of the present invention typically exhibit exposed metal surface area of less than about 0.06 m²/g, more typically less than about 0.048 m²/g and, still more typically, less than about 0.024 m²/g.

[00261] It has been discovered that cobalt-containing catalysts prepared in accordance with the present invention exhibit strong Electron Paramagnetic Resonance (EPR) spectra, in particular strong EPR spectra when analyzed in accordance with Protocol B detailed in Example 35. EPR spectroscopy is a well- known technique for measuring the properties of unpaired electrons in solids and liquids and is described in, for example, Drago, Russell S., "Physical Methods in Chemistry," Saunders Golden Sunburst Series, Chapter 9, W. B. Saunders Company.

[00262] A sample of the cobalt-containing catalyst is placed in a microwave cavity of fixed frequency (e.g., X-band frequency of approximately 9500 MHz, or Q-band frequency of approximately 35 GHz) between the poles of the magnet. The magnetic field is swept through a range chosen to achieve a resonance between the energy required to reverse the electron spin and the microwave frequency of the cavity. The analyses detailed in the present specification and Example 35 used a microwave cavity having a Q- band frequency. The spectra obtained represent the microwave absorption versus the applied magnetic field. To provide a sharper response, these curves are generally presented in terms of the derivative of the microwave absorption versus the applied field. Figs. 109A and 109B represent EPR spectra (of varying spectral windows) obtained for cobalt-containing catalysts of the present invention. The spectra have been adjusted for the setting of the amplifier so that the relative intensity of the spectra are proportional to the EPR responses of the samples.

[00263] It is currently believed that the EPR spectra of the catalysts of the present invention demonstrate that the cobalt is present in the form of a nitride, carbide-nitride, or a combination thereof. As previously noted, EPR is used to analyze substances with unpaired electrons. Thus, the EPR signals are not attributable to any metallic cobalt (i.e., Co⁰) present in the catalysts. Accordingly, the observation of an EPR signal is strong evidence that divalent cobalt (i.e., Co⁺²) is present in the samples since Co⁺³ does not provide an EPR response. Thus, the identification of Co⁺² indicates that the catalyst may contain cobalt oxide, cobalt nitride, or cobalt carbide-nitride .

[00264] However, the nature of the spectra observed is currently believed to rule out the possibility that they are attributable to any cobalt oxide present in the catalyst since the spectra of the cobalt-containing catalysts of the present invention are remarkable in two respects. In particular, the linewidths of the spectra are exceptionally broad, with a peak- to-peak linewidth of over 1000 Gauss in the Q-band spectra, centered near g = 2, with a mixed Gaussian-Lorentzian lineshape. At resonance the microwave energy (hv) is proportional to the applied field, B, but also to a factor, conventionally denoted as g * β, where β is the Bohr magneton. For a description of the g value, and EPR spectroscopy generally, see Transition Ion Electron Paramagnetic Resonance by J. R. Pilbrow, Clarendon Press, Oxford, 1990, pgs 3-7.

[00265] It has been discovered that the spectra linewidths decrease with increasing temperature, a behavior that is known to be characteristic of relatively small ferromagnetic particles (typically less than 10 nm in diameter in their largest dimension) dispersed in a diamagnetic matrix, which exhibit a type of magnetic behavior known as superparamagetism. In this case, activated carbon is the diamagnetic matrix. This phenomenon is described by J. Kliava and R. Berger in the Journal of Magnetism and Magnetic Materials, 1999, 205, 328-42. The narrowing of linewidth with temperature is also described by R. Berger, J. Kliava, J. -C. Bissey, and V Baϊetto in J. Appl . Phys., 2000, 87, 7389-96. Cobalt oxide is not ferromagnetic. Thus, the observation of superparamagnetism rules out assignment of the EPR spectra to cobalt oxide. Accordingly, it is currently believed that the Co⁺² ions are present in a metallic cobalt matrix, which indicates that the counterion, in this case interstitial nitrogen or carbon is present in the metallic matrix too. The second remarkable feature of the EPR spectra of the cobalt-containing catalysts of the present invention is the fact that the observed apparent number of spins per mole of cobalt exceeds Avogadro's number, further proof that the EPR spectra are not attributable to cobalt oxide. In particular, a standard paramagnetic material, C03O₄, was analyzed by Protocol B and found to exhibit spins/mole cobalt generally in accordance with the expected value. This standard has one mole of Co²⁺ and two moles Co³⁺ ions per mole of material, but only the Co²⁺ ions give an EPR signal; thus, in theory, one expects 2.01E23 (0.333 * 6.022E23) spins/mole cobalt with this standard. The standard was found to exhibit approximately 1.64E23 spins per mole cobalt that generally agrees with the spins/mole cobalt expected based on stoichiometry . As shown in Table 38, the intensity of the spectra for the catalysts of the present invention analyzed by Protocol B far exceed this value, providing further proof that the EPR spectra are not attributable to cobalt oxide and, moreover, that the cobalt is present in the form of a cobalt nitride, carbide-nitride, or a combination thereof.

[00266] Furthermore, the fact that the catalysts exhibit more spins than would be predicted based on stoichiometry is evidence that the spins are polarized in a superparamagnetic matrix of a cobalt nitride or carbide-nitride particle since superparamagetism is associated with ferromagnetic materials, which cobalt oxide is not.

[00267] As an overall standard, copper sulfate pentahydrate (CuSO₄ -5H₂O, MW: 249.69 g/mol) was analyzed in Protocol B. The molecular weight of the CuSO₄ ^• 5H₂O sample corresponds to approximately 2.41 * 10²¹ spins per gram catalyst. The spins/gram of this strong pitch (i.e., a solid solution of char in KCl) was measured by Protocol B to be 2.30 * 10²¹ spins per gram catalyst, indicating reliability of the results for the cobalt-containing catalysts analyzed and the conclusions drawn from these results.

[00268] Generally, therefore, cobalt-containing catalysts of the present invention typically exhibit at least about 2.50 x 10²⁵ spins/mole cobalt, at least about 3.00 x 10²⁵ spins/mole cobalt, at least about 3.50 x 10²⁵ spins/mole cobalt, at least about 4.50 x 10²⁵ spins/mole cobalt, at least about 5.50 x 10²⁵ spins/mole cobalt, at least about 6.50 x 10²⁵ spins/mole cobalt, at least about 7.50 x 10²⁵ spins/mole cobalt, at least about 8.50 x 10²⁵ spins/mole cobalt, or at least about 9.50 x 10²⁵ spins/mole cobalt when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B. In various embodiments, catalysts of the present invention exhibit at least about 1.0 x 10²⁶ spins/mole cobalt, at least about 1.25 x 10²⁶ spins/mole cobalt, at least about 1.50 x 10²⁶ spins/mole cobalt, at least about 1.75 x 10²⁶ spins/mole cobalt, at least about 2.0 x 10²⁶ spins/mole cobalt, at least about 2.25 x 10²⁶ spins/mole cobalt, or at least about 2.50 x 10²⁶ spins/mole cobalt when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B. In accordance with any such embodiments, the catalysts of the present invention may be characterized such that the catalyst exhibits less than about 1.0 x 10²⁷ spins/mole cobalt, less than about 7.5 x 10²⁶ spins/mole cobalt, or less than about 5.0 x 10²⁶ spins/mole cobalt when the catalyst is analyzed by EPR Spectroscopy as described in Protocol B.

[00269] Transition metal catalysts of the present invention may exhibit one or more properties described in Ebner et al . , U.S. Patent No. 6,417,133, the entire disclosure of which is hereby incorporated by reference. Such characteristics may be found, for example, at column 3, line 6 to column 7, line 23; column 8, line 27 to column 9, line 24; column 10, lines 53-57; column 11, line 49 to column 14, line 18; column 14, line 50 to column 16, line 3; column 17, line 14 to column 21, line 2; column 26 (Example 2); column 27, lines 21-34 (Example 4); and column 30, line 21 to column 40, line 61 (Examples 7 to 19) .

[00270] Transition metal catalysts of the present invention may include carbon nanotubes on the surface of the carbon support which may contain a certain proportion of the transition metal contained in the catalyst. Additionally or alternatively, the carbon nanotubes may contain a portion of the nitrogen of the transition metal composition. Typically, any such transition metal is present at the root or the tip of the nanotube, however, transition metal may also be present along the length of the nanotube. The carbon nanotubes typically have a diameter of at least about 0.01 μm and, more typically, have a diameter of at least about 0.1 μm. In certain embodiments, the carbon nanotubes have a diameter of less than about 1 μm and, in other embodiments, have a diameter of less than about 0.5 μm.

II. Noble Metal Catalyst

[00271] Generally, the noble metal catalysts utilized in the mixtures and catalyst systems of the present invention include one or more noble metals at a surface of a carbon support. In addition, noble metal catalysts utilized in mixtures of the present invention may include one or more promoter (s) . For example, the noble metal catalysts may be prepared in a manner to exhibit one or more of the properties as described, for example, in U.S. Patent No. 6,417,133, International Publication No. WO 2006/031938, and U.S. Patent No. 6,956,005, the entire contents of which are incorporated herein by reference for all relevant purposes .

[00272] Preferably, the noble metal (s) is selected from the group consisting of platinum (Pt) , palladium (Pd) , ruthenium (Ru) , rhodium (Rh) , iridium (Ir) , silver (Ag) , osmium (Os) , gold (Au) and combinations thereof. In general, platinum and palladium are more preferred, and platinum is most preferred.

[00273] The concentration of noble metal on the carbon support may vary within wide limits. Generally, it is in the range of from about 0.5 to about 20% by weight of the noble metal catalyst. In various embodiments, the concentration of noble metal in the noble metal catalyst is generally in the range of from about 2 to about 10% by weight, preferably from about 2 to about 8% by weight, more preferably from about 4 to about 8% by weight, or even more preferably from about 4 to about 6% by weight of the catalyst. In still other embodiments, the concentration of noble metal ranges from about 2.5% to about 7.5% by weight, or from about 3.5% to about 5% by weight of the noble metal catalyst. Generally, the noble metal constitutes less than about 8% by weight of the catalyst, typically less than about 7% by weight of the catalyst, more typically less than about 6% by weight of the catalyst. In various embodiments, the noble metal typically constitutes from about 1% to about 8% by weight of the catalyst, more typically from about 2% to about 7% by weight of the catalyst and, still more typically, from about 3% to about 6% by weight of the catalyst.

[00274] In general, the carbon supports of the noble metal catalyst of the present invention are well-known in the art and include those described above as suitable for use in a transition metal catalyst as detailed herein. For example, activated, non-graphitized carbon supports are preferred and the form of the carbon support is not critical (e.g., the support may be a monolithic support or a particulate support) .

[00275] In various particularly preferred embodiments, the supports are in the form of particulates . Because particulate supports are especially preferred, most of the following discussion focuses on embodiments which use a particulate support. It should be recognized, however, that the present invention is not limited to the use of particulate supports.

[00276] The specific surface area of the carbon support, measured by the Brunauer-Emmett-Teller (BET) method using N₂, is typically from about 10 to about 3000 m²/g (surface area of carbon support per gram of carbon support) , more typically from about 500 to about 2100 m²/g, and still more typically from about 750 to about 2100 m²/g or from about 1000 to about 2100 m²/g. In certain embodiments, the preferred specific surface area is from about 500 to about 1500 m²/g, 1000 to about 1500 m²/g, from about 1100 to about 1500 m²/g, from about 1200 to about 1500 m²/g, from about 1200 to about 1400 m²/g, or about 1400 m²/g.

[00277] Carbon supports for use in the present invention are commercially available from a number of sources, including those noted above regarding suitable supports for transition metal catalysts .

[00278] As noted, in addition to the noble metal, one or more promoters may be at the surface of the carbon support. Although the promoter typically is deposited onto the surface of the carbon support, other sources of promoter may be used (e.g., the carbon support itself may naturally contain a promoter) . A promoter tends to increase catalyst selectivity, activity, and/or stability. The presence of one or more promoters, particularly when alloyed with the noble metal, tends to reduce noble metal leaching.

[00279] The promoter (s), for example, may be an additional noble metal (s) at the surface of the carbon support. For example, ruthenium and palladium have been found to act as promoters on a catalyst comprising platinum deposited at a carbon support surface. Alternatively, the promoter (s) may be a metal selected from the group consisting of tin (Sn) , cadmium (Cd) , magnesium (Mg) , manganese (Mn) , nickel (Ni) , aluminum (Al), cobalt (Co), bismuth (Bi), lead (Pb), titanium (Ti), antimony (Sb) , selenium (Se) , iron (Fe) , rhenium (Re) , zinc (Zn) cerium (Ce) , zirconium (Zr) , tellurium (Te) , germanium (Ge) and combinations thereof. Preferably, the promoter is selected from the group consisting of iron, bismuth, tin, titanium and cobalt. In a preferred embodiment, the promoter is tin. In an additional preferred embodiment, the promoter is titanium. In various embodiments, a noble metal catalyst is combined in a mixture with a transition metal-containing catalyst that includes a transition metal that may also be utilized as a promoter in the noble metal catalyst (e.g., iron and/or cobalt) . In accordance with this discussion, a promoter refers to a metal provided by a source other than the transition metal catalyst.

[00280] The amount of promoter (s) at the surface of the carbon support for the noble metal (whether promoter (s) are associated with the carbon surface itself, noble metal, or a combination thereof) may vary within wide limits depending on, for example, the noble metal (s) and promoter (s) used. Generally, a promoter is present in a proportion of at least about 0.05 % by weight but less than about 10% by weight of the noble metal catalyst. Proportions of promoter less than 0.05% by weight generally do not promote the activity of the catalyst over an extended period of time. On the other hand, promoter weight percents greater than about 10% tend to decrease the activity of the catalyst. Typically, a promoter is present in a proportion of at least about 0.1% by weight, at least about 0.25% by weight, at least about 0.5% by weight, at least about 0.6% by weight or at least about 0.75% by weight. Generally, a promoter is present in a proportion of from about 0.1 to about 4% by weight, from about 0.25 to about 4% by weight, from about 0.25 to about 3% by weight, from about 0.25 to about 2.5% by weight, from about 0.5 to about 2.5% by weight, from about 0.5 to about 1.5% by weight, or from about 0.5 to about 1% by weight of the catalyst. Typically, at least one surface promoter is present at a concentration of from about 0.05% to about 5%, from about 0.1% to about 2%, or from about 0.1% to about 1% by weight of the noble metal catalyst. Generally, at least one promoter (e.g., iron) constitutes less than about 2% by weight of the catalyst, less than about 1.5% by weight of the catalyst, less than about 1% by weight of the catalyst, less than about 0.5% by weight of the catalyst, or about 0.4% by weight of the catalyst. Typically, at least one promoter constitutes less than about 1% by weight of the catalyst, preferably from about 0.25% to about 0.75% by weight of the catalyst and, more preferably, from about 0.25% to about 0.6% by weight of the catalyst. In various preferred embodiments, the catalyst includes iron as a promoter. Additionally or alternatively, the catalyst includes cobalt as a promoter .

[00281] In various particularly preferred embodiments, the catalyst comprises both iron and cobalt promoters. Use of iron and cobalt generally provides benefits associated with use of iron (e.g., activity and stability with respect to formaldehyde and formic acid oxidation) . However, as compared to the presence of iron alone as a promoter, the presence of cobalt tends to reduce formation of certain by-products during oxidation of a PMIDA substrate (e.g., IDA) . Moreover, IDA formation is believed to be directly related to total iron content of the catalyst. Thus, in various iron/cobalt co- promoter embodiments, iron content is essentially replaced by cobalt to reduce formation of IDA and other by-products while nevertheless providing sufficient activity towards oxidation of formaldehyde and formic acid. For example, as compared to a platinum on carbon catalyst containing 0.5% by weight iron in the absence of cobalt, a similar catalyst containing 0.25% by weight iron and 0.25% by weight cobalt typically provides comparable activity for PMIDA, formaldehyde and formic acid oxidation, while minimizing by-product formation. [00282] In iron/cobalt co-promoter embodiments, the amount of each promoter at the surface of the carbon support of the noble metal catalyst (whether associated with the carbon surface itself, noble metal, or a combination thereof) is typically at least about 0.05% by weight, at least about 0.1% by weight or at least about 0.2% by weight. Furthermore, the amount of iron at the surface of the carbon support is typically from about 0.1 to about 4% by weight of the catalyst, preferably from about 0.1 to about 2% by weight of the catalyst, more preferably from about 0.1 to about 1% by weight of the catalyst and, even more preferably, from about 0.1 to about 0.5% by weight of the catalyst. Similarly, the amount of cobalt at the surface of the carbon support is typically from about 0.1 to about 4% by weight of the catalyst, preferably from about 0.1 to about 2% by weight of the catalyst, more preferably from about 0.2 to about 1% by weight of the catalyst and, even more preferably, from about 0.2 to about 0.5% by weight of the catalyst. In such an embodiment, the weight ratio of iron to cobalt in the catalyst is generally from about 0.1:1 to about 1.5:1 and preferably from about 0.2:1 to about 1:1. For example, the catalyst may comprise about 0.1% by weight iron and about 0.4% by weight cobalt or about 0.2% by weight iron and about 0.2% by weight cobalt.

[00283] As understood by those skilled in the art, the metal content of the catalysts can be freely controlled within the ranges described herein (e.g., by adjusting the concentration and relative proportions of the metal source (s) used in a liquid phase reactive deposition bath) .

A. Noble Metal Catalyst Features

[00284] In particularly preferred embodiments of this invention, the noble metal is alloyed with at least one promoter to form alloyed metal particles. For example, noble metal particles at a surface of the carbon support comprise noble metal atoms alloyed with promoter atoms. In various other preferred embodiments, the noble metal is alloyed with two promoters (e.g., iron and cobalt) . A catalyst comprising a noble metal alloyed with one or more promoters tends to have all the advantages discussed above with respect to catalysts comprising a promoter. However, catalysts comprising a noble metal alloyed with one or more promoters tend to exhibit greater resistance to metal leaching and further stability (e.g., from cycle to cycle) with respect to formaldehyde and formic acid oxidation .

[00285] The term "alloy" encompasses any metal particle comprising a noble metal and at least one promoter, irrespective of the precise manner in which the noble metal and promoter atoms are disposed within the particle (although it is generally preferable to have a portion of the noble metal atoms at the surface of the alloyed metal particle) . The alloy may be, for example, any of the following:

1. An intermetallic compound. An intermetallic compound is compound comprising a noble metal and a promoter (e.g., Pt₃Sn).

2. A substitutional alloy. A substitutional alloy has a single, continuous phase, irrespective of the concentrations of the noble metal and promoter atoms. Typically, a substitutional alloy contains noble metal and promoter atoms which are similar in size (e.g., platinum and silver; or platinum and palladium) . Substitutional alloys are also referred to as "monophasic alloys."

3. A multiphasic alloy. A multiphasic alloy is an alloy that contains at least two discrete phases. Such an alloy may contain, for example Pt₃Sn in one phase, and tin dissolved in platinum in a separate phase.

4. A segregated alloy. A segregated alloy is a metal particle wherein the particle stoichiometry varies with distance from the surface of the metal particle. 5. An interstitial alloy. An interstitial alloy is a metal particle wherein the noble metal and promoter atoms are combined with non-metal atoms, such as boron, carbon, silicon, nitrogen, phosphorus, etc.

[00286] In various embodiments, the noble metal particles comprise noble metal atoms alloyed with at least one promoter (e.g., iron and/or cobalt) in the form of an alloy selected from the group consisting of an intermetallic compound, a substitutional alloy, a multiphasic alloy, an interstitial alloy, and combinations thereof.

[00287] The alloyed metal particles need not have a uniform composition and the compositions may vary from particle to particle, or even within the particles themselves. In addition, the noble metal catalyst may further comprise particles consisting of the noble metal alone or the promoter alone. Nevertheless, it is preferred that the composition of metal particles be substantially uniform from particle to particle and within each particle, and that the number of noble metal atoms in intimate contact with promoter atoms be maximized. It is also preferred, although not essential, that the majority of noble metal atoms at the surface of the carbon support be alloyed with a promoter in the noble metal particles, and more preferred that substantially all of the noble metal atoms at the surface of the carbon support be alloyed with a promoter in the noble metal particles. It is further preferred, although not essential, that the alloyed metal particles be uniformly distributed at the surface of the carbon support.

[00288] As taught by Ebner et al., in U.S. Patent No. 6,417,133, oxygen-containing functional groups (e.g., carboxylic acids, ethers, alcohols, aldehydes, lactones, ketones, esters, amine oxides, and amides) at the surface of the carbon support increase noble metal leaching and potentially increase noble metal sintering during liquid phase oxidation reactions and thus reduce the ability of the catalyst to oxidize oxidizable substrates, particularly formaldehyde during the PMIDA oxidation reaction. As used herein, an oxygen-containing functional group is "at the surface of the carbon support" if it is bound to an atom of the carbon support and is able to chemically or physically interact with compositions within the reaction mixture or with the metal atoms deposited on the carbon support. [00289] Many of the oxygen-containing functional groups that reduce noble metal resistance to leaching and sintering and reduce the activity of the catalyst desorb from the carbon support as carbon monoxide when the catalyst is heated at a high temperature (e.g., 900⁰C) in an inert atmosphere (e.g., helium or argon) . Thus, measuring the amount of CO desorption from a fresh catalyst (i.e., a catalyst that has not previously been used in a liquid phase oxidation reaction) under high temperatures is one method that may be used to analyze the surface of the catalyst to predict noble metal retention and maintenance of catalyst activity. One way to measure CO desorption is by using thermogravimetric analysis with in-line mass spectroscopy ("TGA-MS"). Preferably, no more than about 1.2 mmole of carbon monoxide per gram of catalyst desorb from the catalyst of the present invention when a dry, fresh sample of the catalyst in a helium atmosphere is subjected to a temperature which is increased from about 20⁰C to about 900⁰C at about 10⁰C per minute, and then held constant at about 900⁰C for about 30 minutes. More preferably, no more than about 0.7 mmole of carbon monoxide per gram of fresh catalyst desorb under those conditions, even more preferably no more than about 0.5 mmole of carbon monoxide per gram of fresh catalyst desorb, and most preferably no more than about 0.3 mmole of carbon monoxide per gram of fresh catalyst desorb. A catalyst is considered "dry" when the catalyst has a moisture content of less than about 1% by weight. Typically, a catalyst may be dried by placing it into a N₂ purged vacuum of about 25 inches of Hg and a temperature of about 120⁰C for about 16 hours.

[00290] Measuring the number of oxygen atoms at the surface of a fresh catalyst support is another method to analyze the catalyst to predict noble metal retention and maintenance of catalytic activity. Using, for example, x-ray photoelectron spectroscopy, a surface layer of the support which is about 50 A in thickness is analyzed. Preferably, a ratio of carbon atoms to oxygen atoms at the surface (as measured by currently available equipment for x-ray photoelectron spectroscopy) of at least about 20:1 (carbon atoms: oxygen atoms) is suitable in the noble metal catalysts described herein. More preferably, the ratio is at least about 30:1, even more preferably at least about 40:1, even more preferably at least about 50:1, and most preferably at least about 60:1. In addition, the ratio of oxygen atoms to metal atoms at the surface (again, as measured by currently available equipment for x-ray photoelectron spectroscopy) preferably is less than about 8:1 (oxygen atoms imetal atoms) . More preferably, the ratio is less than 7:1, even more preferably less than about 6:1, and most preferably less than about 5:1.

[00291] Regardless of whether the promoter is alloyed to the noble metal, it is currently believed that the promoter tends to become oxidized if the catalyst is exposed to an oxidant over a period of time. For example, an elemental tin promoter tends to oxidize to form Sn(II)O, and Sn(II)O tends to oxidize to form Sn(IV)O₂. This oxidation may occur, for example, if the catalyst is exposed to air for more than about 1 hour. Although such promoter oxidation has not been observed to have a significant detrimental effect on noble metal leaching, noble metal sintering, catalyst activity, or catalyst stability, it does make analyzing the concentration of detrimental oxygen- containing functional groups at the surface of the carbon support more difficult. For example, as discussed herein, the concentration of detrimental oxygen-containing functional groups (i.e., oxygen-containing functional groups that reduce noble metal resistance to leaching and sintering, and reduce the activity of the catalyst) may be determined by measuring (using, for example, TGA-MS) the amount of CO that desorbs from the catalyst under high temperatures in an inert atmosphere. However, it is currently believed that when an oxidized promoter is present at the surface, the oxygen atoms from the oxidized promoter tend to react with carbon atoms of the support at high temperatures in an inert atmosphere to produce CO, thereby creating the illusion of more detrimental oxygen-containing functional groups at the surface of the support than actually exist. Such oxygen atoms of an oxidized promoter also can interfere with obtaining a reliable prediction of noble metal leaching, noble metal sintering, and catalyst activity from the simple measurement (via, for example, x-ray photoelectron spectroscopy) of oxygen atoms at the catalyst surface.

[00292] Thus, when the noble metal catalyst comprises at least one promoter which has been exposed to an oxidant and thereby has been oxidized (e.g., when the catalyst has been exposed to air for more than about 1 hour) , it is preferred that the promoter first be substantially reduced (thereby removing the oxygen atoms of the oxidized promoter from the surface of the catalyst) before attempting to measure the amount of detrimental oxygen-containing functional groups at the surface of the carbon support. This reduction preferably is achieved by heating the catalyst to a temperature of about 500⁰C for about 1 hour in an atmosphere consisting essentially of H₂. The measurement of detrimental oxygen-containing functional groups at the surface preferably is performed (a) after this reduction, and (b) before the surface is exposed to an oxidant following the reduction. Most preferably, the measurement is taken immediately after the reduction.

[00293] Suitable methods used to prepare noble metal catalysts are described, for example, in Wan et al . International Publication No. WO 2006/031938 and U.S. Patent No. 6,417,133 to Ebner et al . , the entire disclosures of which are incorproated herein by reference for all relevant purposes.

[00294] The total exposed metal surface area of noble metal catalysts may be within the ranges described by Wan et al . as determined using static carbon monoxide chemisorption analysis. For example, noble metal catalysts subjected to such analysis are generally characterized as chemisorbing less than about 50 μmoles of carbon monoxide per gram of catalyst and, more generally, less than about 45 μmoles of carbon monoxide per gram of catalyst. Typically, catalysts of the present invention subjected to such analysis are characterized as chemisorbing less than about 40 μmoles of carbon monoxide per gram of catalyst, preferably less than about 35 μmoles of carbon monoxide per gram of catalyst, more preferably less than about 30 μmoles of carbon monoxide per gram of catalyst, still more preferably less than about 25 μmoles of carbon monoxide per gram of catalyst and especially less than about 20 μmoles of carbon monoxide per gram of catalyst during the second cycle which is indicative of the total exposed noble metal (e.g., Pt) at the surface of the carbon support.

[00295] Exposed metal surface area (m² per gram catalyst) may be determined from the volume of CO chemisorbed using the equation set forth above. Noble metal catalysts suitable for use in accordance with the present invention generally exhibit exposed metal surface area of less than about 1.2 m²/g and, more generally, exhibit exposed metal surface area of less than about 1.1 m²/g. Typically, the noble metal catalysts exhibit exposed metal surface area of less than about 1.0 m²/g, more typically less than about 0.85 m²/g and, even more typically, less than about 0.75 m²/g .

[00296] In addition to the above-noted features, noble metal catalysts utilized in the present invention may exhibit any or all of the additional features set forth in Wan et al . International Publication No. WO 2006/031938.

Ill . Mixtures Including Transition Metal and Noble Metal Catalysts

[00297] As previously noted, the present invention is directed to mixtures including a transition metal-containing catalyst exhibiting one or more of the properties detailed elsewhere herein and a noble metal-containing catalyst prepared as detailed elsewhere herein. For example, in various embodiments, the present invention is directed to a mixture including a catalyst containing approximately 3% cobalt and comprising a transition metal composition as detailed herein along with a catalyst including platinum and iron and/or cobalt at a surface of a carbon support.

[00298] As noted, both the transition metal catalyst and noble metal catalyst are effective to catalyze oxidation of PMIDA and formaldehyde and formic acid by-products of PMIDA oxidation. Often, the transition metal catalyst component of the mixture is more effective for oxidation of PMIDA than the noble metal catalyst component, while the noble metal catalyst component is often more effective for catalyzing by-product oxidation. Combining these catalysts capitalizes on the advantageous properties of each catalyst. For example, as compared to PMIDA oxidation catalyzed by a noble metal- containing catalyst alone, replacement of a portion of the noble metal catalyst with the transition metal catalyst does not result in any unacceptable loss, if any, in PMIDA oxidation effectiveness, while requiring a reduced proportion of costly noble metal. The effectiveness of the noble metal catalyst with regard to by-product oxidation justifies its expense. Likewise, as compared to PMIDA oxidation catalyzed by a transition metal- containing catalyst alone, the effectiveness of the noble metal catalyst for by-product oxidation justifies its expense, while its effectiveness for PMIDA oxidation avoids an unacceptable loss, if any, in PMIDA oxidation activity.

[00299] Generally, the weight ratio of transition metal catalyst to noble metal catalyst is at least about 0.1:1, at least about 0.25:1, at least about 0.5:1, at least about 0.75:1, or at least about 1:1. Typically, the weight ratio of transition metal catalyst to noble metal catalyst in the mixture is from about 0.1:1 to about 20:1, more typically from about 0.5:1 to about 10:1, still more typically from about 0.75:1 to about 5:1 and, even more typically, about 1:1.

[00300] In various embodiments the transition metal catalyst is mixed with used noble metal catalyst (i.e., noble metal catalyst that has been used in one or more previous oxidation reactions) . In various other embodiments, the noble metal catalyst is mixed with used transition metal catalyst.

IV. Use of a Supplemental Promoter

[00301] In accordance with the present invention, it has been discovered that certain metals and/or metal compounds function as supplemental promoters in liquid-phase oxidation reactions catalyzed by a mixture of a transition metal catalyst and a noble metal catalyst.

[00302] Typically, the supplemental promoter (s) comprise a metal selected from the group consisting of tin, cadmium, magnesium, manganese, ruthenium, nickel, copper, aluminum, cobalt, bismuth, lead, titanium, antimony, selenium, iron, rhenium, zinc, cerium, zirconium, tellurium, sodium, potassium, vanadium, gallium, tantalum, niobium, rubidium, cesium, lanthanum, and/or germanium. Additionally or alternatively, the supplemental promoter may comprise a metal compound comprising one or more of these metals. In various embodiments, at least two supplemental promoters are utilized. It is often preferred for the supplemental promoter (s) to be bismuth, lead, germanium, tellurium, titanium, copper and/or nickel. In various preferred embodiments, the promoter comprises bismuth and/or tellurium.

[00303] In particular, it has been found that such supplemental promoters are effective in enhancing the capability of these catalyst mixtures for catalyzing the oxidation of PMIDA substrates and formaldehyde and formic acid by-products of PMIDA oxidation. As previously noted, it is currently believed that the mixtures detailed herein are effective for oxidation of PMIDA substrates and formaldehyde and formic acid by-products by taking advantage of the effectiveness of the transition metal catalyst for oxidation of the PMIDA substrate and the effectiveness of the noble metal catalyst for oxidation of the formaldehyde and formic acid by-products. For example, it is currently believed that the combination of a supplemental promoter and the catalyst mixture enhances PMIDA and by-product oxidation by modestly retarding oxidation of the PMIDA substrate by the noble metal catalyst, thereby providing greater opportunity for oxidation of the by-products by the noble metal catalyst believed to be superior to the transition metal catalyst in this regard. For example, without being bound to a particular theory, the promoter may obstruct access of the PMIDA substrate to the surface of the noble metal catalyst thereby allowing greater access of formaldehyde and/or formic acid. Any retardation of PMIDA oxidation by the noble metal catalyst may be compensated for by the presence of the transition metal catalyst that is effective for this purpose independently of the noble metal catalyst. In addition, it is currently believed that the presence of the supplemental promoter is effective to enhance the catalytic oxidation of these by-products by the noble metal catalyst, especially for the conversion of formic acid to CO2.

[00304] It is to be noted that reference to effectiveness of the transition metal catalyst for oxidation of the PMIDA substrate does not ignore its activity for by-product oxidation, as these catalysts have in fact been shown to be effective for this purpose. Likewise, capitalizing on the activity of the noble metal catalyst for by-product oxidation does not ignore its activity for oxidation of the PMIDA substrate.

[00305] Bismuth as a supplemental promoter may be particularly effective for improving the effectiveness of catalyst mixtures of the present invention for oxidation of formaldehyde and formic acid by-products of PMIDA oxidation. In addition, tellurium as a supplemental promoter has been observed to be effective for modestly retarding the oxidation of the PMIDA substrate, thereby providing greater opportunity for oxidation of by-products by the noble metal-containing catalyst. Without being bound to a particular theory, it is currently believed that tellurium, especially modest amounts, may slightly slow the oxidative cleavage of the PMIDA substrate as compared to conventional noble metal on carbon oxidation catalysts, and mixtures including a transition metal catalyst and a noble metal catalyst in the absence of tellurium as a supplemental promoter. At the same time, tellurium does not substantially effect, or at least diminishes to a much lesser extent, the rate of by-product oxidation by the noble metal catalyst, or mixture of the present invention including a noble metal-containing catalyst and a transition metal-containing catalyst. Various preferred embodiments of the present invention utilize bismuth and tellurium as supplemental promoters to equilibrate the rates of the concurrent reactions of the PMIDA substrate and by-products thereof. More particularly, utilizing bismuth and tellurium may provide a suitable balance between PMIDA substrate and byproduct oxidation to balance productivity concerns and issues associated with less than preferred by-product oxidation (e.g., participation by formaldehyde and formic acid in side reactions that result in a decrease in glyphosate yield) .

[00306] Introduction of bismuth and tellurium to an oxidation reaction medium or mixture as supplemental promoters may occur concurrently or sequentially. However, in various preferred embodiments, introduction of bismuth begins (and may be completed) prior to introduction of tellurium. Addition of bismuth commences capitalizing on its effectiveness with regard to oxidation of formaldehyde and formic acid by-products, while subsequent addition of tellurium and the attendant modest retardation of PMIDA oxidation may equilibrate PMIDA substrate and by-product oxidation rates. The precise manner of sequential introduction of the promoters (e.g., the interval between introduction of each promoter) may be selected depending on the particular reaction conditions that prevail. In addition, depending on the reaction conditions, introduction of tellurium may begin (and may be completed) prior to introduction of bismuth.

[00307] It is to be noted that noble metal-containing catalysts suitable for use in mixtures and systems of the present invention, and previously described as suitable for use in combination with a supplemental promoter, may comprise a promoter along with the noble metal. In various embodiments the noble metal catalyst incorporated in the mixtures and systems of the present invention include platinum along with iron and/or cobalt at a surface of the carbon support. Reference to a "supplemental promoter" herein refers to a promoter that is mixed with the noble metal-containing catalyst or a mixture including the noble metal catalyst, rather than a promoter at the surface of the noble metal-containing catalyst as initially prepared. For example, the supplemental promoter may be mixed with the noble metal-containing catalyst and/or transition metal-containing catalyst directly in an oxidation reaction medium or mixture where an oxidation reaction being catalyzed by the noble metal and/or transition metal catalyst is taking place. Alternatively, for example, this mixing may take place separately from the oxidation reaction, such as in a holding tank. In various instances, the catalyst (s) and supplemental promoter may be mixed in the absence of any liquid medium to form a dry catalyst mixture.

[00308] The mixing of the supplemental promoter (s), transition metal catalyst and/or noble metal catalyst preferably is conducted in a liquid medium. As noted above, this mixing may, for example, be conducted directly in a liquid oxidation reaction medium where an oxidation reaction being catalyzed by the transition metal catalyst and/or noble metal catalyst is taking place. Where, however, the oxidation reaction is carried out under pressure, the reaction vessel is normally sealed and it is consequently often more preferred to mix the catalyst (s) with the supplemental promoter separately from the reaction vessel, such as in a catalyst holding or recycle tank.

[00309] Typically, the supplemental promoter is introduced into the mixing liquid in the form of an inorganic or organic compound containing the supplemental promoter. The promoter- containing compound may be soluble or insoluble in the liquid, but most typically is at least partially soluble. The functional group combined with the supplemental promoter atom is generally not critical (although it preferably is an agronomically acceptable functional group) . Typically, for example, suitable compounds include oxides, hydroxides, salts of inorganic hydracids, salts of inorganic oxy-acids, salts of aliphatic or aromatic organic acids, and phenates. [00310] Suitable bismuth-containing compounds, for example, include inorganic or organic compounds wherein the bismuth atom(s) is at an oxidation level greater than 0 (e.g., 2, 3, 4 or 5), most preferably 3. Examples of such suitable bismuth compounds include:

1. Bismuth oxides. These include, for example, BiO, Bi₂C>3, Bi₂O₄, Bi₂O₅, and the like.

2. Bismuth hydroxides. These include, for example, Bi(OH)₃ and the like.

3. Bismuth salts of inorganic hydracids . These include, for example, bismuth chloride (e.g., BiCl₃) , bismuth bromide (e.g., BiBr₃) , bismuth iodide (e.g., BiI₃) , bismuth telluride (e.g., Bi₂Te₃), and the like. Bismuth halides are typically less preferred because they tend to be corrosive to the process equipment .

4. Bismuth salts of inorganic oxy-acids . These include, for example, bismuth sulphite (e.g., Bi₂ (SO₃) ₃»Bi₂0₃»5H₂0) , bismuth sulphate (e.g. , Bi₂ (SO₄) ₃), bismuthyl sulfate (e.g. , (BiO)HSO₄), bismuthyl nitrite (e.g., (BiO) NO₂»0.5H₂O) , bismuth nitrate (e.g., Bi (NO₃) ₃»5H₂O, also known as "bismuth nitrate pentahydrate") , bismuthyl nitrate (e.g., (BiO)NO₃, also known as "bismuth subnitrate," "bismuth nitrate oxide," and "bismuth oxynitrate") , double nitrate of bismuth and magnesium (e.g.,

2Bi (NO₃) ₃»3Mg (NO₃) ₂»24H₂O) , bismuth phosphite (e.g. , Bi₂ (PO₃H) ₃»3H₂O) , bismuth phosphate (e.g. , BiPO₄), bismuth pyrophosphate (e.g., Bi₄ (P₂O₇) ₃), bismuthyl carbonate (e.g., (BiO)₂CO₃, also known as "bismuth subcarbonate") , bismuth perchlorate (e.g., Bi (ClO₄) ₃»5H₂O) , bismuth antimonate (e.g., BiSbO₄), bismuth arsenate (e.g., Bi (AsO₄) ₃), bismuth selenite (e.g. , Bi₂ (SeO₂) ₃), bismuth titanate (e.g. , Bi₂O₃»2TiO₂) , and the like. These salts also include bismuth salts of oxy-acids derived from transition metals, including, for example, bismuth vanadate (e.g., BiVO₄) , bismuth niobate (e.g., BiNbO₄) , bismuth tantalate (BiTaO₄), bismuth chromate (Bi₂(CrO₄), bismuthyl dichromate (e.g., (BiO)₂Cr₂O₇), bismuthyl chromate (e.g., H(BiO)CrO₄), double chromate of bismuthyl and potassium (e.g., K(BiO)CrO₄), bismuth molybdate (e.g., Bi₂ (MoO₄) ₃), double molybdate of bismuth and sodium (e.g., NaBi (MoO₄) ₂) , bismuth tungstate (e.g., Bi₂ (WO₄) 3), bismuth permanganate (e.g., Bi₂O₂(OH)MnO₄), bismuth zirconate (e.g., 2Bi₂O₃»3ZrO₂) , and the like.

5. Bismuth salts of aliphatic or aromatic organic acids. These include, for example, bismuth acetate (e.g., Bi (C₂H₃O₂) ₃) , bismuthyl propionate (e.g., (BiO)C₃H₅O₂), bismuth benzoate (e.g., C₆H₅CO₂Bi(OH)₂), bismuthyl salicylate (e.g. , C₆H₄CO₂(BiO) (OH)), bismuth oxalate (e.g., (C₂O₄) 3Bi₂), bismuth tartrate (e.g.,

Bi₂ (C₄H₄O₆) ₃»6H₂O) , bismuth lactate (e.g. , (C₆H₉O₅) OBi»7H₂O) , bismuth citrate (e.g., C₆H₅O₇Bi), and the like.

6. Bismuth phenates . These include, for example, bismuth gallate (e.g., C₇H₇O₇Bi) , bismuth pyrogallate (e.g., C₆H₃(OH)₂(OBi) (OH)), and the like.

7. Miscellaneous other organic and inorganic bismuth compounds. These include, for example, bismuth phosphide (e.g., BiP) , bismuth arsenide (Bi₃As₄) , sodium bismuthate (e.g., NaBiO₃) , bismuth-thiocyanic acid (e.g.,

H₂(Bi(BNS)₅)^H₃(Bi(CNS)₆)), sodium salt of bismuth-thiocyanic acid, potassium salt of bismuth-thiocyanic acid, trimethylbismuthine (e.g., Bi (CH₃) 3), triphenylbismuthine (e.g., Bi (C₆H₅) ₃), bismuth oxychloride (e.g., BiOCl), bismuth oxyiodide

(e.g. , BiOI), and the like.

[00311] In various embodiments, the bismuth compound is a bismuth oxide, bismuth hydroxide, or bismuth salt of an inorganic oxy-acid. More preferably, the bismuth compound is bismuth nitrate (e.g., Bi (NO₃) ₃»5H₂O) , bismuthyl carbonate (e.g.,

(BiO)₂CO₃), or bismuth oxide (e.g., Bi₂O₃), with bismuth (III) oxide (i.e., Bi₂Os) being most preferred because it contains no counterion which can contaminate the final reaction product. [00312] Suitable tellurium-containing compounds, for example, include inorganic or organic compounds wherein the tellurium atom(s) is at an oxidation level greater than 0 (e.g., 2, 3, 4, 5 or 6), most preferably 4. Examples of such suitable tellurium compounds include:

1. Tellurium oxides. These include, for example, TeO₂, Te₂O₃, Te₂O₅, TeO₃, and the like.

2. Tellurium salts of inorganic hydracids. These include, for example, tellurium tetrachloride (e.g., TeCl₄) , tellurium tetrabromide (e.g., TeBr₄) , tellurium tetraiodide (e.g., TeI₄) , and the like.

3. Tellurium salts of inorganic oxy-acids. These include, for example, tellurious acid (e.g., H₂TeO₃) , telluric acid (e.g., H₂TeO₄ or Te(OH)₆), tellurium nitrate (e.g. , Te₂O₄^HNO₃), and the like.

4. Miscellaneous other organic and inorganic tellurium compounds. These include, for example, dimethyl tellurium dichloride, lead tellurium oxide, tellurium isopropoxide, ammonium tellurate, tellurium thiourea, and the like.

[00313] In various embodiments, the tellurium compound is a tellurium oxide or tellurium salt of an inorganic hydracid. More preferably, the tellurium compound is tellurium dioxide (e.g., TeO₂) , tellurium tetrachloride (e.g., TeCl₄) , or telluric acid (e.g., Te(OH)₆), with tellurium tetrachloride being most preferred.

[00314] The preferred amount of the supplemental promoter introduced into the reaction zone depends on, for example, the mass of the carbon-supported, noble-metal-containing catalyst (i.e., the total mass of the carbon support, noble metal, and any other component of the catalyst) ; mass of the transition metal catalyst; mass of the total reaction feed mixture; and/or the concentration of the oxidation substrate.

[00315] In general, the ratio of the mass of the metallic component of the supplemental promoter (e.g., bismuth) to the mass of the carbon-supported, noble-metal-containing catalyst or transition metal catalyst charged to the reactor is generally at least about 1:15,000, at least about 1:10,000, or at least about 1:5000. Typically, the mass ratio of the metallic component supplemental promoter to the noble metal catalyst or transition metal catalyst is at least about 1:2500, more typically at least about 1:2000, still more typically at least about 1:1500 and, even more typically, at least about 1:1000. In various embodiments, the mass ratio of the metallic component of the supplemental promoter to both the noble metal catalyst and transition metal catalyst satisfies these limits. Although it is also feasible to practice the present invention without detriment to the oxidation reaction when ratios of the mass of supplemental promoter to the mass of either or both catalyst are as great as about 1:750, about 1:500, about 1:300, and even greater than about 1:200, 1:100, 1:50 or 1:40, the lower ratios noted above are believed to be effective for most applications.

[00316] The ratio of the mass of the supplemental promoter to the total reaction mass charged to the reactor is preferably at least about 1:1,000,000; more preferably at least about 1:100,000; even more preferably at least about 1:40,000; and most preferably from about 1:40,000 to about 1:15,000. Although ratios greater than 1:8,000 may normally be used without detriment to the oxidation reaction, it is generally preferred for the ratio to be less than 1:8,000 (particularly where bismuth is the supplemental promoter) .

[00317] The ratio of the mass of the supplemental promoter to the mass of the oxidation substrate (e.g., PMIDA or a salt thereof) charged to the reactor is preferably at least about 1:100,000; more preferably 1:10,000; even more preferably at least about 1:4,000; and most preferably from about 1:4,000 to about 1:2,000. Although ratios greater than 1:1,000 may normally be used without detriment to the oxidation reaction, it is generally preferred for the ratio to be less than 1:1,000 (particularly where bismuth is the supplemental promoter) .

[00318] Where a mixture of particulate noble metal and transition metal catalysts are used for the reaction, the catalysts and the supplemental promoter may be charged to a liquid reaction medium in which the reaction is conducted. For example, in the preparation of N- (phosphonomethyl) glycine (glyphosate) , the catalysts and supplemental promoter may be charged to an aqueous reaction medium containing N- (phosphonomethyl) iminodiacetic acid (PMIDA), and oxygen then introduced to the reaction medium for catalytic oxidation of PMIDA to glyphosate. The supplemental promoter may be charged in a mass ratio to the catalyst charge of at least about 1:15,000, preferably at least about 1:5000, more preferably at least about 1:2500, and most preferably at least about 1:1000.

[00319] Where the oxidation reactions are conducted in a stirred tank reactor in which the noble metal and/or transition metal catalyst are slurried in the reaction medium, the catalyst is separated from the reaction mixture, preferably by filtration, and recycled to the reactor for further oxidation of PMIDA and the aforesaid by-products. Such a stirred tank reactor system may be operated in either a batch or continuous mode. Alternatively, a fixed or fluidized catalyst bed can be used. In a continuous process, PMIDA, formaldehyde and formic acid are all oxidized in a continuous reaction zone to which an aqueous reaction medium comprising PMIDA is continuously or intermittently supplied and a reaction mixture comprising glyphosate is continuously or intermittently withdrawn, the supplemental promoter being continuously or intermittently introduced into the reaction zone.

[00320] It has been observed that addition of a discrete charge of supplemental promoter to the first batch of a series of successive batch reaction cycles is effective to enhance the activity of a noble metal-containing catalyst and/or a mixture including such a catalyst for oxidation of formic acid and formaldehyde throughout a substantial series of reaction cycles, without further addition of supplemental promoter from any external source. It has further been observed that the supplemental promoter is present in recycled noble metal catalyst, apparently having been deposited thereon by adsorption to the noble metal and/or the carbon support. Only a fraction of the supplemental promoter added to the first batch of the series can be found on the catalyst after multiple cycles. However, when supplemental promoter is introduced into the first batch in the amounts described above, the fraction remaining on the noble metal catalyst is apparently sufficient for promoting the oxidation of formaldehyde and formic acid throughout a substantial series of batches in which the noble metal catalyst recycled from an earlier batch is substantially the sole source of supplemental promoter for the successive batch reaction cycles of the series. It has been found that a single addition of supplemental promoter in a mass ratio to the noble metal and/or transition metal catalyst of approximately 1:2500 is effective for promotion of by-product oxidation in series of 20 or more, typically 50 or more, more typically over 100, batch reaction cycles. Thereafter, a further discrete charge of supplemental promoter optionally may be added to the reaction medium for a subsequent batch constituting the first of another series of batch oxidation reaction cycles in which the recycle catalyst (s) from an earlier batch of such further series becomes substantially the sole source of promoter for the successive batch reaction cycles of the further series of batch reactions.

[00321] Similarly, where supplemental promoter is added to the reaction medium in a continuous stirred tank reactor, addition of supplemental promoter in a single discrete amount is effective to enhance the effectiveness of the noble metal catalyst and/or mixture for formaldehyde and formic acid oxidation throughout multiple turnovers in reactor volume during a continuous reaction run. No further addition of supplemental promoter is made until the start of a second reaction run. For this purpose, a reaction run consists of the period of oxidation of formaldehyde and formic acid from the time of any discrete addition of supplemental promoter to the reaction zone until the time of the next succeeding addition of supplemental promoter to the reaction zone, and may typically consist of 50 or more, more typically over 100, turnovers of the working volume of the reactor.

[00322] As noted, only a fraction of the supplemental promoter added to the first batch of a cycle remains on the noble metal catalyst after multiple cycles of a series of batch reaction runs, or after multiple turnovers of a continuous reaction run. However, the supplemental promoter remains effective to enhance the oxidation of a substrate comprising formaldehyde, or especially formic acid, if the substrate is contacted with the oxidizing agent in a reaction zone which comprises the liquid reaction medium and wherein the mass ratio of supplemental promoter to the noble metal catalyst in such reaction zone is at least about 1:200,000, preferably at least about 1:70,000, more preferably at least about 1:30,000, most preferably at least about 1:15,000. Inasmuch as substantially the sole source of supplemental promoter for the reactor may be recycle catalyst, it is further preferred that the supplemental promoter be present on or in the recycle catalyst in the same mass ratios, i.e., at least about 1:200,000, preferably at least about 1:70,000, more preferably at least about 1:30,000, most preferably at least about 1:15,000.

[00323] The supplemental promoter content of the reaction zone may also be expressed as a mass ratio to the noble metal component of the noble metal catalyst. For example, for a 5% noble metal on carbon catalyst, the ratio of supplemental promoter to noble metal is generally at least about 1:10,000, typically at least about 1:3500, more typically about 1:1800 and, still more typically, about 1:700. These preferences generally prevail over the range of noble metal content of the noble metal on carbon catalyst, which is typically from about 0.5 to 20% noble metal. However, where the noble metal content is relatively high, e.g., approaching 20%, the supplemental promoter may be effective in relatively lower mass ratios to the noble metal component, even as low as 1:40,000.

[00324] The supplemental promoter content of the reaction zone may also be expressed as a mass ratio to the transition metal component of the transition metal catalyst. For example, for a transition metal catalyst including 3% by weight cobalt, the ratio of supplemental promoter to transition metal is generally at least about 1:6000 or at least about 1:4000, typically at least about 1:2000, more typically about 1:1000 and, still more typically, about 1:500.

[00325] Where the supplemental promoter is added in a discrete charge at the start of a series of batch reaction cycles, or at the beginning of a continuous reaction run as defined above, it may be added in a mass ratio to the noble metal component of the catalyst of at least about 1:750, preferably at least about 1:250, more preferably at least about 1:125, most preferably at least about 1:50. As indicated above, the preferred ratio of supplemental promoter to noble metal may vary with the noble metal content of the catalyst. Thus, e.g., when the noble metal content of the catalyst approaches 20% by weight, the supplemental promoter may be effective when added at a mass ratio to noble metal of 1:3000 or higher, more preferably at least about 1:1000, 1:500 or 1:200.

[00326] Periodic discrete additions of supplemental promoter may be advantageous because excessive proportions of supplemental promoter, while maximizing the effectiveness of the noble meal catalyst for the oxidation of formaldehyde and formic acid, as noted, may retard the oxidation of PMIDA. By adding supplemental promoter only periodically, the proportions of supplemental promoter deposited on the catalyst and present in the reaction zone may decay fairly rapidly to a residual quasi- steady state range wherein the supplemental promoter remains effective to enhance catalytic activity for the oxidation of formaldehyde or formic acid without significantly retarding the rate or extent of oxidation of PMIDA. In fact, while the mass ratio preferences stated above apply to the oxidation of formaldehyde and formic acid, the preferred ratio may fall in an intermediate optimum range for a reaction comprising the conversion of PMIDA to glyphosate. Thus, the optimum supplemental promoter content (e.g., weight ratio of metal component of the supplemental promoter to the noble metal catalyst) within the PMIDA oxidation reaction zone, and on the recycle catalyst for such reaction, may be lower than 1:15,000, for example, in a range of 1:65,000 to 1:25,000.

[00327] Deposit of supplemental promoter on the surface of a noble metal on carbon catalyst in the reaction medium results in formation of a novel catalyst complex comprising the catalyst and the promoter. The catalyst component of the noble metal catalyst complex may further comprise a surface promoter comprising a metal different from the supplemental promoter or, in some instances, comprising the same metal. The supplemental promoter is believed to be deposited by adsorption from the reaction medium, and remains desorbable from the catalyst surface into the catalyst medium. While an operative fraction of residual supplemental promoter resists desorption to remain adhered to the catalyst through multiple reaction cycles (or through an extended run of a continuous reaction system) as explained hereinabove, the supplemental promoter is typically more desorbable than the surface promoter which is applied in the catalyst preparation process.

[00328] The noble metal catalyst generally is prepared in the first instance by depositing noble metal and optionally surface promoter onto a carbon support to form a catalyst precursor, then reducing the catalyst precursor to produce the reaction catalyst. The novel catalyst complex is formed by subsequent deposition of supplemental promoter on the catalyst, typically by adsorption to the carbon or noble metal surface. Advantageously, the supplemental promoter is mixed with the catalyst in the reaction medium so that the promoter is deposited from the reaction medium onto the catalyst surface. However, it will be understood that, in the alternative, the supplemental promoter can be premixed with the transition metal and/or noble metal catalyst in another liquid medium to form the catalyst complex, after which the catalyst complex may be introduced into the reaction medium for use in conducting the oxidation reaction.

[00329] It should be recognized that, depending on the desired effects, more than one supplemental promoter may be used (e.g., bismuth and tellurium). In addition, each supplemental promoter may come from more than one source. Further, the carbon-supported, noble-metal-containing catalyst may already contain an amount of metal on its surface which is the same metal as the supplemental promoter, such as where (a) the catalyst is manufactured with such a metal on its surface to act as a catalyst-surface promoter, or (b) the catalyst is a used catalyst which has been recovered from a previous reaction mixture where the metal was present (e.g., as a supplemental promoter) .

[00330] In a particularly preferred embodiment, the carbon-supported, noble-metal-containing catalyst itself also comprises one or more catalyst-surface promoters on its surface, as described above. Where the noble metal catalyst is being used in the oxidation of a PMIDA compound and the supplemental promoter is bismuth, it is particularly preferred for the noble metal catalyst to contain iron and/or cobalt.

[00331] In many instances, after a supplemental promoter and a carbon-supported, noble-metal-containing catalyst have been combined, at least a portion of the supplemental promoter deposits onto the surface of the carbon support and/or noble metal of the catalyst, and is consequently retained by the catalyst. Because the catalyst retains the promoter, the catalyst may typically be recycled for use in catalyzing the oxidation of subsequent amounts of the oxidation substrate (e.g., the catalyst may be used to oxidize additional batches of the oxidation substrate, or may be used in a continuous oxidation process) while still retaining the benefits of the supplemental promoter. And, as the effects of the supplemental promoter decrease over time with use, replenishing amounts of fresh supplemental promoter may periodically be mixed with the noble metal catalyst to revive the effects and/or achieve other desired results (e.g., decreased formic acid levels) . Where, for example, the catalyst is used in multiple batch reactions, such periodic replenishing may, for example, be conducted after the catalyst has been used in at least about 20 batch oxidation reactions (more preferably after it has been used in at least about 30 batch oxidation reactions, and most preferably after it has been used in at least about 100 or more batch oxidation reactions) . Where a catalyst is periodically replenished with fresh supplemental promoter, the mixing for replenishment may be conducted during, or, more preferably, separately from the oxidation reaction being catalyzed by the catalyst.

[00332] In a particularly preferred embodiment, a supplemental promoter is mixed with used catalyst (i.e., catalyst that has been used in one or more previous oxidation reactions) . Typically, the activity and/or desired selectivity of a catalyst decreases with use over several cycles. Thus, for example, the activity of a carbon-supported, noble-metal- containing catalyst for oxidizing byproducts (e.g., formaldehyde and/or formic acid) of the PMIDA oxidation reaction often tends to decrease as the catalyst is used, thereby causing less formic acid and/or formaldehyde to be destroyed, and, consequently, a greater amount of NMG to be produced. Eventually, in fact, this activity will decrease to a level where an unacceptable amount of formic acid and/or formaldehyde is not oxidized, consequently often causing an unacceptable amount of NMG compounds to be produced (i.e., the selectivity of the catalyst for making N- (phosphonomethyl) glycine compounds from PMIDA will decrease to an unacceptable level) . Traditionally, when the catalyst activity for oxidizing the byproducts reaches such a point, the catalyst has been deemed unusable, and, consequently, has either been regenerated (i.e., reactivated) through a time-consuming and sometimes costly process, or discarded altogether. It has been discovered in accordance with this invention, however, that such a catalyst can be "revived" (i.e., the selectivity of the catalyst for making the N- (phosphonomethyl) glycine compound can be increased to an acceptable level) by mixing the catalyst with a supplemental promoter, particularly bismuth or tellurium. In other words, the supplemental promoter can be used to modify the catalyst performance and extend the life of the catalyst.

[00333] As noted, it has been observed that a supplemental promoter (particularly bismuth) may cause a slight decrease in the oxidation rate of PMIDA. In such an instance, the oxidation rate may typically be increased, at least in part, by increasing the amount of oxygen fed into the reacting mixture, maintaining a relatively high oxygen flow rate for an extended period during the reaction, increasing the pressure, and/or adding transition metal catalyst. Where, however, the oxygen flow is increased, it preferably is not increased to an extent which causes the catalyst surface to become detrimentally over-oxidized. Thus, the increased oxygen feed rate preferably is maintained at a level such that at least about 40% (more preferably at least about 60%, even more preferably at least about 80%, and most preferably at least about 90%) of the fed oxygen is utilized.

V. Catalyst Combinations

[00334] In various embodiments, the present invention is directed to catalyst combinations comprising a secondary transition metal-containing catalyst and a primary transition metal-containing catalyst comprising a transition metal composition (e.g., cobalt nitride) formed on a carbon support, prepared generally in accordance with the above discussion and also described in Liu et al . International Publication No. WO 2005/016519, U.S. 2005/0176989 Al, Arhancet et al . International Publication No. WO 2006/089193, and U.S. 2006/0229466 Al, the entire disclosures of which are hereby incorporated by reference. Generally, these combinations are advantageous since the primary catalyst is effective for oxidizing PMIDA, formaldehyde, and formic acid, while not requiring the presence of a costly noble metal, and the secondary catalyst enhances the oxidation of formaldehyde and/or formic acid by products, and is believed to help control the undesired formation of hydrogen. More particularly it is believed that the secondary catalyst is effective to promote oxidation of formaldehyde and formic acid by hydrogen peroxide formed in the reduction of molecular oxygen catalyzed by the primary catalyst. Thus, such a catalyst combination may potentially provide a more economical process.

[00335] In accordance with certain embodiments in which the primary catalyst includes a primary active phase comprising a transition metal composition prepared generally in accordance with the above discussion and described in U.S. Serial No. 10/919,028, the secondary catalyst includes a secondary active phase comprising a secondary catalytic composition formed on a carbon support in accordance with the above discussion. In various particularly preferred embodiments, the secondary transition metal is titanium. Thus, the secondary active phase comprises a secondary transition metal composition which may include any or all of titanium nitride, titanium carbide, or titanium carbide-nitride, in accordance with the discussion set forth above.

[00336] Typically, such a catalyst combination comprises at least about 10% by weight of a secondary catalyst described herein, more typically at least about 20% by weight and, most typically from about 20 to about 50% by weight, basis the catalyst combination as a whole. Additionally, the catalyst combination comprises at least about 10% by weight of the primary catalyst of the present invention, more typically at least about 20% by weight and, most typically, from about 20 to about 50% by weight of the primary catalyst.

[00337] In accordance with various other embodiments of catalyst combinations in which the primary catalyst includes a transition metal composition prepared generally in accordance with the above discussion and described in U.S. Serial No. 10/919,028, the secondary catalyst comprises a titanium- containing zeolite. Typically, such a catalyst combination comprises at least about 10% by weight of a secondary catalyst described herein, more typically at least about 20% by weight and, most typically from about 20 to about 50% by weight, basis the catalyst combination as a whole. Additionally, the catalyst combination comprises at least about 10% by weight of the primary catalyst of the present invention, more typically at least about 20% by weight and, most typically, from about 20 to about 50% by weight of the primary catalyst.

[00338] Generally in such catalysts titanium is incorporated into the lattice or, molecular structure, of a silicon- containing zeolite by replacing silicon atoms of the lattice by isomorphous substitution. Titanium atoms contained in a secondary active phase may be subject to formation of coordination compounds (i.e., chelation) with either N- (phosphonomethyl) iminodiacetic acid or

N- (phosphonomethyl) glycine present in the reaction medium. In particular, titanium atoms present for example, as TiO₂ on a support, and also titanium atoms substituted in the lattice at the exterior of a zeolite particle are believed to be susceptible to chelation and leaching from the lattice. However, titanium substituted in the lattice in the interior of the zeolite particle is generally less subject to leaching than titanium at the exterior, especially where the pore size of the zeolite is within the preferred ranges described hereinbelow. Thus, preferably, the zeolite lattice comprises substantial substitution with titanium atoms in regions of the zeolite lattice located within the interior of the catalyst particle.

[00339] Preferably, the pores of the titanium-containing zeolite are of a size sufficient to permit access of formaldehyde, formic acid and hydrogen peroxide while also allowing egress of carbon dioxide produced by the oxidation of formaldehyde and/or formic acid from the pores. However, the pores are preferably not so large as to permit access of N- (phosphonomethyl) iminodiacetic acid or N- (phosphonomethyl) glycine . Preventing access of these compounds to the interior of the catalyst particle avoids chelation of titanium atoms present in the interior lattice. As a result, leaching of titanium is minimized, but titanium contained within the particle interior remains available and effective for oxidizing low molecular weight compounds such as formaldehyde and formic acid. Preferably, the pores of the titanium-containing zeolite have a pore diameter of less than about 100 A, more preferably less than about 50 A, still more preferably less than about 25 A and, even more preferably, less than about 10 A.

[00340] In certain embodiments, to promote ease of handling the catalyst (e.g., filtering), it is preferred for the zeolite particles to have a size distribution similar to that of the carbon support particles. Typically, at least about 95% of the zeolite particles are from about 10 to about 500 nm in their largest dimension, more typically at least about 95% of the zeolite particles are from about 10 to about 200 nm in their largest dimension and, still more typically, at least about 95% of the zeolite particles are from about 10 to about 100 nm in their largest dimension.

[00341] Titanium-containing catalysts (e.g., synthetic zeolites and molecular sieves containing titanium) have been discovered to be useful in catalysis of various oxidation reactions, particularly in conjunction with hydrogen peroxide as an oxidant. For example, titanium-containing zeolites have been reported as effective for the oxidation of alkanes (P. A. Jacobs et al, Nature, 345, 240-242 (1990)), oxidation of primary alcohols to aldehydes and secondary alcohols to ketones (U.S. Pat. No. 4,480,135), epoxidation of olefins (EP Patent No. 100,119), hydroxylation of aromatic compounds (Great Britain Patent No. 2,116,974 and Tangaraj et al . , Appl . Catal . 57 (1990) Ll), and oxidation of aniline (Tuel et al., Appl. Catal., A: 118(2) 173-186 (1994)) in the presence of hydrogen peroxide as an oxidant. Titanium-containing zeolites are generally prepared by isomorphous substitution of titanium into the framework of a zeolite. Molecular sieves and synthetic zeolites are described, for example, in Kirk-Othmer Encyclopedia of Chemical Technology; 4th Edition, John Wiley & Sons, New York, p. 1330-1333, 1999. Various titanium-containing zeolites are prepared by replacing silicon atoms of "silicalite" with titanium atoms. "Silicalite" is a zeolite structure constituted by pure crystalline SiC>₂ and has been described, for example, by Flanigen E. M. (Nature 271, 512 (1978) ) .

[00342] Titanium-containing silicates of differing crystal structures are known in the art. Suitable titanium-containing zeolites may comprise any of a variety of crystal structures including, for example, TS-I which has a MFI crystal structure (i.e., ZSM-5 zeolite) and TS-2 which has a MEL crystal structure (i.e., ZSM-Il zeolite), and beta (β) crystal structures. MFI (ZSM-5) and MEL (ZSM-Il) zeolite structures are well-known in the art. TS-I has been found to be effective in the oxidation of various organic compounds using aqueous hydrogen peroxide as an oxidant including, for example, oxidation of alkanes, oxidation of primary alcohols to aldehydes and oxidation of secondary alcohols to ketones.

[00343] TS-I includes titanium silicalite having a formula of xTiθ2* (1-x) SiC>2 with x generally being from about 0.0001 to about 0.04. TS-I has an MFI crystal structure. Other titanium- containing zeolites known in the art include TS-2 (titanium silicalite having an MEL crystal structure) and MCM-41. These and other titanium containing zeolites are described, for example, in U.S. Patent No. 3,702,886 to Argauer et al . , U.S. Patent No. 4,410,501 to Taramasso et al . , U.S. Patent No. 4,526,878 to Takegami et al . , U.S. Patent No. 5,098,684 to Kresge et al . , U.S. Patent No. 5,500,199 to Takegami et al . , U.S. Patent No. 5,525,563 to Thiele et al., U.S. Patent No. 5,977,009 to Faraj, U.S. Patent No. 6,106,803 to Hasenzahl et al., U.S. Patent No. 6,391,278 to Pinnavaia et al . , U.S. Patent No. 6,403,514 to Mantegazza et al . , U.S. Patent No. 6,667,023 to Ludvig, U.S. Patent Nos. 6,841,144 and 6,849,570 to Hasenzahl et al . , the entire disclosures of which are hereby incorporated by reference. Suitable secondary catalysts containing titanium silicalite (i.e., TS-I) may be prepared generally in accordance with the procedures described in Yap, N., et al . , "Reactivity and Stability of Au in and on TS-I for Epoxidation of Propylene with H₂ and O₂," Journal of Catalysis, 2004, Pages 156-170, Volume 226, Elsevier Inc. including, for example, TS-I catalysts of varying Si/Ti ratios and/or crystallite size. In various embodiments, TS-I catalysts prepared in this manner may have a Si/Ti ratio of at least about 10, at least about 15, at least about 20, or at least about 30. In various such embodiments the Si/Ti ratio of the TS-I containing catalyst is from about 10 to about 40 or from about 15 to about 30. Additionally or alternatively, TS-I containing catalysts prepared in this manner may have a crystallite size of about 300 x 450 nm, or about 300 x 400 nm.

[00344] In addition to TS-I and TS-2, titanium-containing zeolites described in the above-referenced patents include, for example, EUROTS-I (also described, for example, in J. A. Martens et al., Applied Catalysis A: General, 99 (1993) 71-84) and a titanium substituted analog of β-zeolite (also described, for example, in Corma et al . , J. Chem. Soc. Chem. Commun . , 589-590 (1992)), and titanium-substituted MCM-41 (described, for example, in U.S. Patent No. 6,391,278 to Pinnavaia et al . and U.S. Patent No. 5,098,684 to Kresge et al.).

[00345] The present invention is further directed to catalyst combinations comprising a secondary catalyst (e.g., a catalyst comprising titanium nitride formed on a carbon support or a titanium-containing zeolite) and a noble-metal containing bifunctional catalyst (i.e., a catalyst effective both for oxidation of PMIDA and oxidation of formaldehyde and formic acid byproducts) as described in U.S. Patent No. 6,417,133 to Ebner et al . , the entire disclosure of which is incorporated by reference as stated above. The catalysts described by Ebner et al . have been proven to be highly advantageous and effective for PMIDA oxidation and the further oxidation of by-product formaldehyde and/or formic acid. Secondary catalysts described herein are also effective for oxidation of by-product formaldehyde and/or formic acid. Thus, combination of the catalysts described by Ebner et al . with a secondary catalyst described herein may be advantageous, particularly in the event hydrogen peroxide is generated in PMIDA oxidation catalyzed by a catalyst described by Ebner et al .

[00346] Typically, such a catalyst combination comprises at least about 10% by weight of a bifunctional catalyst as described in U.S. Patent No. 6,417,133, more typically at least about 20% by weight and, most typically from about 10 to about 50% by weight, basis the catalyst combination as a whole. Additionally, the catalyst combination comprises at least about 10% by weight of a secondary transition metal-containing catalyst of the present invention, more typically at least about 20% by weight and, most typically, from about 20 to about 50% by weight of a secondary transition metal-containing catalyst of the present invention.

[00347] The present invention is also directed to catalyst combinations comprising a secondary transition metal-containing catalyst (e.g., a catalyst comprising titanium nitride formed on a carbon support or a titanium-containing zeolite) and an activated carbon catalyst as described in U.S. Patent Nos. 4,264,776 and 4,696,772 to Chou, the entire disclosures of which are hereby incorporated by reference. Generally, the catalysts described in U.S. Patent Nos. 4,264,776 and 4,696,772 comprise activated carbon treated to remove oxides from the surface thereof. Oxides removed include carbon functional groups containing oxygen and hetero atom functional groups containing oxygen. The procedure for removing oxides from particulate activated carbon is typically commenced by contacting the carbon surface with an oxidizing agent selected from the group consisting of liquid nitric acid, nitrogen dioxide, CrC>3, air, oxygen, H₂O₂, hypochlorite, a mixture of gases obtained by vaporizing nitric acid, or combinations thereof to produce labile oxides at the carbon surface. The oxidized carbon is then heated while in contact with an atmosphere comprising nitrogen, steam, carbon dioxide, or combinations thereof. In various embodiments oxides are removed from the surface of the activated carbon catalyst in one step which includes heating the catalyst while in contact with an atmosphere comprising oxygen and a nitrogen-containing compound including, for example, an atmosphere which contains ammonia and water vapor.

[00348] The activated carbon catalyst described by Chou is effective to oxidize PMIDA while the secondary catalyst provides oxidation of formaldehyde and formic acid byproducts, while not requiring the presence of costly noble metal. Thus, combination of the catalysts described by Chou with a secondary catalyst described herein may be advantageous, particularly in the event hydrogen peroxide is generated in PMIDA oxidation catalyzed by a catalyst described by Chou.

[00349] Typically, such a catalyst combination comprises at least about 10% by weight of a catalyst as described in U.S. Patent Nos. 4,264,776 and 4,696,772, more typically at least about 20% by weight and, most typically from about 20 to about 50% by weight, basis the catalyst combination as a whole. Additionally, the catalyst combination comprises at least about 10% by weight of a secondary transition metal-containing catalyst of the present invention, more typically at least about 20% by weight and, most typically, from about 20 to about 50% by weight of a secondary transition metal-containing catalyst of the present invention.

VI . Oxidation Reactions

[00350] Generally, catalysts, mixtures, catalyst systems, and catalyst combinations of the present invention are suitable for use in reactions which may be catalyzed by a noble metal- containing catalyst due to the similarity between the electronic nature of the transition metal composition (e.g., cobalt nitride) and noble metals. More particularly, catalysts, mixtures, catalyst systems, and catalyst combinations of the present invention may be used for liquid phase oxidation reactions. Examples of such reactions include the oxidation of alcohols and polyols to form aldehydes, ketones, and acids

(e.g., the oxidation of 2-propanol to form acetone, and the oxidation of glycerol to form glyceraldehyde, dihydroxyacetone, or glyceric acid) ; the oxidation of aldehydes to form acids

(e.g., the oxidation of formaldehyde to form formic acid, and the oxidation of furfural to form 2-furan carboxylic acid) ; the oxidation of tertiary amines to form secondary amines (e.g., the oxidation of nitrilotriacetic acid ("NTA") to form iminodiacetic acid ("IDA")); the oxidation of secondary amines to form primary amines (e.g., the oxidation of IDA to form glycine); and the oxidation of various acids (e.g., formic acid or acetic acid) to form carbon dioxide and water.

[00351] The catalysts, mixtures, catalyst systems, and catalyst combinations disclosed herein are particularly suited for catalyzing the liquid phase oxidation of a tertiary amine to a secondary amine, for example in the preparation of glyphosate and related compounds and derivatives. For example, the tertiary amine substrate may correspond to a compound of Formula I having the structure:

wherein R¹ is selected from the group consisting of R⁵OC(O)CH₂- and R⁵OCH₂CH₂-, R² is selected from the group consisting of R⁵OC(O)CH₂-, R⁵OCH₂CH₂-, hydrocarbyl, substituted hydrocarbyl, acyl, -CHR⁶PO₃R⁷R⁸, and -CHR⁹SO₃R¹⁰, R⁶, R⁹ and R¹¹ are selected from the group consisting of hydrogen, alkyl, halogen and -NO₂, and R³, R⁴, R⁵, R⁷, R⁸ and R¹⁰ are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl and a metal ion. Preferably, R¹ comprises R⁵OC(O)CH₂-, R¹¹ is hydrogen, R⁵ is selected from hydrogen and an agronomically acceptable cation and R² is selected from the group consisting of R⁵OC(O)CH₂-, acyl, hydrocarbyl and substituted hydrocarbyl. As noted above, transition metal catalysts of the present invention and mixtures including such catalysts are particularly suited for catalyzing the oxidative cleavage of a PMIDA substrate such as

N- (phosphonomethyl) iminodiacetic acid or a salt thereof to form N- (phosphonomethyl) glycine or a salt thereof. In such an embodiment, the transition metal catalyst, mixture, and/or noble metal catalyst included in the mixture are effective for oxidation of byproduct formaldehyde to formic acid, carbon dioxide and/or water.

[00352] For example, in various embodiments, transition metal catalysts of the present invention are characterized by their effectiveness for catalyzing the oxidation of formaldehyde such that a representative aqueous solution having a pH of about 1.5 and containing 0.8% by weight formaldehyde and 0.11% by weight of a transition metal catalyst of the present invention is agitated and sparged with molecular oxygen at a rate of 0.75 cm³ oxygen/minute/gram aqueous mixture at a temperature of about 100⁰C and pressure of about 60 psig, typically at least about 5%, more typically at least about 10%, still more typically at least about 15% and, even more typically, at least about 20% or at least about 30% of the formaldehyde is converted to formic acid, carbon dioxide and/or water. Transition metal catalysts of the present invention are characterized in various embodiments by their effectiveness for oxidation of formaldehyde in the presence of N- (phosphonomethyl) iminodiacetic acid. For example, when a representative aqueous solution having a pH of about 1.5 and containing 0.8% by weight formaldehyde, 5.74% by weight N- (phosphonomethyl) iminodiacetic acid, and 0.11% by weight of a transition metal catalyst of the present invention is agitated and sparged with molecular oxygen at a rate of 0.75 cm³ oxygen/minute/gram aqueous mixture at a temperature of about 100⁰C and pressure of about 60 psig, typically at least about 50%, more typically at least about 60%, still more typically at least about 70%, and, even more typically at least about 80% or at least about 90% of the formaldehyde is converted to formic acid, carbon dioxide and/or water.

[00353] More particularly, it is believed that transition metal-containing catalysts, mixtures and/or catalyst combinations of the present invention provide improved oxidation of formaldehyde and/or formic acid byproducts produced during PMIDA oxidation. In particular, it is believed that peroxides can be generated in the course of catalytic reduction of molecular oxygen during the oxidation of PMIDA to N- (phosphonomethyl) glycine utilizing certain transition metal- containing catalysts. These peroxides include, for example, hydrogen peroxide and may further include peroxide derivatives such as per-acids . Oxidation of PMIDA to glyphosate comprises a four electron transfer in the catalytic reduction of oxygen. However, a portion of molecular oxygen introduced into the reaction medium may undergo only a two electron transfer yielding hydrogen peroxide or other peroxides . Four electron and two electron reduction of molecular oxygen are shown in the following equations, respectively.

O₂ + 4H⁺ + 4e^~ -> 2H₂O E₀ = 1.299 V O₂ + 2H⁺ + 2e^~ -> H₂O₂ E₀ = 0.67 V

[00354] Formation of hydrogen peroxide is generally undesired as it may be reduced to yield hydrogen, an undesired byproduct. Titanium-based catalysts are effective for the oxidation of various substrates, particularly in the presence of hydrogen peroxide as an oxidant. These various substrates include, for example, primary alcohols and aldehydes. Thus, in various preferred embodiments of the present invention, titanium is incorporated as a secondary transition metal into the transition metal catalyst, or a secondary catalyst including titanium is incorporated into a catalyst combination along with the transition metal catalyst in order to utilize the hydrogen peroxide as an oxidant for oxidation of formaldehyde and/or formic acid byproducts to produce carbon dioxide and/or water. Additionally or alternatively, oxidation of formaldehyde in the presence of hydrogen peroxide may proceed via intermediate formation of performic acid, which may also function as an oxidant for formaldehyde oxidation. Advantageously, operation in this manner reduces formaldehyde and formic acid byproduct formation and hydrogen generation.

[00355] Hydrogen peroxide generation has not been identified as an issue in connection with PMIDA oxidation in the presence of noble metal catalysts. Thus, mixtures of the present invention are currently believed to generate lower levels of hydrogen peroxide than those generated in PMIDA oxidation catalyzed by mixtures of the present invention, if any hydrogen peroxide is generated at all. In fact, it is currently believed that the noble metal catalyst of the mixture may be effective to remove any hydrogen peroxide generated in PMIDA oxidation utilizing a mixture in accordance with the present invention. But it should be understood that it is currently believed that hydrogen peroxide generated in connection with mixtures of the present invention may also be effectively dealt with utilizing the strategies detailed herein (e.g., use of a titanium catalyst) .

[00356] It is to be noted that this discussion concerning hydrogen peroxide is based on experimental data for PMIDA utilizing a transition metal catalyst in the absence of any other catalyst, particularly in the absence of a noble metal catalyst. Generation of hydrogen peroxide has not been observed in connection with use of a noble metal catalyst, or a mixture including a transition metal catalyst and a noble metal catalyst. This represents an unpredictable result associated with use of the mixture including the transition metal catalyst since one skilled in the art may expect some hydrogen peroxide generation based on the results for PMIDA oxidation in the presence of the transition metal catalyst alone.

[00357] Transition metal catalysts of the present invention have been observed to combine activity for oxidation of an organic substrate with retention of the transition metal component of the catalyst throughout one or more reaction cycles. This combination of the activity for oxidation with resistance to leaching is defined herein as the ratio of the proportion of transition metal removed from the catalyst during a first or subsequent reaction cycle (s) to the substrate content of the reaction mixture upon completion of a first or subsequent reaction cycle (s) (i.e., the leaching/activity ratio). For example, transition metal catalysts of the present invention may be characterized such that when an aqueous mixture containing 0.15% by weight of the catalyst and about 5.75% by weight N- (phosphonomethyl) iminodiacetic is agitated and sparged with molecular oxygen at a rate of 0.875 cm³ oxygen/minute/gram aqueous mixture and sparged with nitrogen at a rate of 0.875 cm³ nitrogen/minute/gram aqueous mixture at a temperature of about 100⁰C and a pressure of about 60 psig for from 30 to 35 minutes for a first reaction cycle, the transition metal catalyst exhibits a leaching/activity ratio during the first reaction cycle of generally less than about 1, less than about 0.75, less than about 0.50, less than about 0.25, or less than about 0.225. Typically, transition metal catalysts of the present invention exhibit a leaching/activity ratio under such conditions of less than about 0.2, more typically less than about 0.175, still more typically less than about 0.15 or less than about 0.125, even more typically less than about 0.1 or less than about 0.075. In various embodiments, transition metal catalysts of the present invention exhibit a leaching/activity ratio under such conditions of less than about 0.050, less than about 0.025, less than about 0.015, less than about 0.010, or less than about 0.08. Further in accordance with such embodiments, transition metal catalysts of the present invention may generally exhibit a leaching/activity ratio during one or more reaction cycles subsequent a first reaction cycle of less than about 0.5, less than about 0.4, less than about 0.3, less than about 0.2, or less than about 0.1. Typically, transition metal catalysts of the present invention exhibit a leaching/activity ratio during one or more reaction cycles subsequent a first reaction cycle of less than about 0.075, more typically less than about 0.05, still more typically less than about 0.018 or less than about 0.015 and, even more typically, less than about 0.010 or less than about 0.008. A. Reaction Conditions

[00358] The above-described catalysts, mixtures, systems, and catalyst combinations are especially useful in liquid phase oxidation reactions at pH levels less than 7, and in particular, at pH levels less than 3. One such reaction is the oxidation of PMIDA or a salt thereof to form

N- (phosphonomethyl) glycine or a salt thereof in an environment having pH levels in the range of from about 1 to about 2. This reaction is often carried out in the presence of solvents which solubilize noble metals and, in addition, the reactants, intermediates, or products often solubilize noble metals. Various catalysts (and combinations) of the present invention avoid these problems due to the absence of a noble metal.

[00359] The description below discloses with particularity the use of mixtures including catalysts described above containing at least one transition metal composition (e.g., a transition metal nitride, transition metal carbide or transition metal carbide-nitride) or containing a single transition metal composition comprising a plurality of transition metal compositions. The description below likewise applies to the use of catalyst combinations of the present invention including a primary catalyst containing a transition metal composition combined with a secondary catalyst, and mixtures including such a catalyst combination. It should be understood that reference to "catalyst" in the description below refers to individual catalysts, mixtures of catalysts, catalyst systems, and catalyst combinations of the present invention. It should be recognized, however, that the principles disclosed below are generally applicable to other liquid phase oxidative reactions, especially those at pH levels less than 7 and those involving solvents, reactants, intermediates, or products which solubilize noble metals . [00360] As is recognized in the art, the liquid phase oxidation of N- (phosphonomethyl) iminodiacetic acid substrates may be carried out in a batch, semi-batch or continuous reactor system containing one or more oxidation reaction zones. The oxidation reaction zone(s) may be suitably provided by various reactor configurations, including those that have back-mixed characteristics, in the liquid phase and optionally in the gas phase as well, and those that have plug flow characteristics. Suitable reactor configurations having back-mixed characteristics include, for example, stirred tank reactors, ejector nozzle loop reactors (also known as venturi-loop reactors) and fluidized bed reactors. Suitable reactor configurations having plug flow characteristics include those having a packed or fixed catalyst bed (e.g., trickle bed reactors and packed bubble column reactors) and bubble slurry column reactors. Fluidized bed reactors may also be operated in a manner exhibiting plug flow characteristics. The configuration of the oxidation reactor system, including the number of oxidation reaction zones and the oxidation reaction conditions are not critical to the practice of the present invention. Suitable oxidation reactor systems and oxidation reaction conditions for liquid phase catalytic oxidation of an N- (phosphonomethyl) iminodiacetic acid substrate are well-known in the art and described, for example, by Ebner et al . , U.S. Patent No. 6,417,133, by Leiber et al . , U.S. Patent No. 6,586,621, and by Haupfear et al., U.S. Patent No. 7,015,351, the entire disclosures of which are incorporated herein by reference .

[00361] To begin the PMIDA oxidation reaction, it is preferable to charge the reactor with the PMIDA reagent (i.e., PMIDA or a salt thereof), catalyst (e.g., a mixture including a transition metal catalyst and noble metal catalyst) , and a solvent in the presence of oxygen. The solvent is most preferably water, although other solvents (e.g., glacial acetic acid) are suitable as well.

[00362] The reaction may be carried out in a wide variety of batch, semi-batch, and continuous reactor systems. The configuration of the reactor is not critical. Suitable conventional reactor configurations include, for example, stirred tank reactors, fixed bed reactors, trickle bed reactors, fluidized bed reactors, bubble flow reactors, plug flow reactors, and parallel flow reactors.

[00363] When conducted in a continuous reactor system, the residence time in the reaction zone can vary widely depending on the specific catalyst and conditions employed. Typically, the residence time can vary over the range of from about 3 to about 120 minutes. Preferably, the residence time is from about 5 to about 90 minutes, and more preferably from about 5 to about 60 minutes. When conducted in a batch reactor, the reaction time typically varies over the range of from about 15 to about 120 minutes. Preferably, the reaction time is from about 20 to about 90 minutes, and more preferably from about 30 to about 60 minutes .

[00364] In a broad sense, the oxidation reaction may be practiced in accordance with the present invention at a wide range of temperatures, and at pressures ranging from sub- atmospheric to super-atmospheric. Use of mild conditions (e.g., room temperature and atmospheric pressure) has obvious commercial advantages in that less expensive equipment may be used. However, operating at higher temperatures and super- atmospheric pressures, while increasing capital requirements, tends to improve phase transfer between the liquid and gas phase and increase the PMIDA oxidation reaction rate.

[00365] Preferably, the PMIDA reaction is conducted at a temperature of from about 20 to about 180⁰C, more preferably from about 50 to about 140⁰C, and most preferably from about 80 to about 110⁰C. At temperatures greater than about 180⁰C, the raw materials tend to begin to slowly decompose.

[00366] The pressure used during the PMIDA oxidation generally depends on the temperature used. Preferably, the pressure is sufficient to prevent the reaction mixture from boiling. If an oxygen-containing gas is used as the oxygen source, the pressure also preferably is adequate to cause the oxygen to dissolve into the reaction mixture at a rate sufficient such that the PMIDA oxidation is not limited due to an inadequate oxygen supply. The pressure preferably is at least equal to atmospheric pressure. More preferably, the pressure is from about 30 to about 500 psig, and most preferably from about 30 to about 130 psig.

[00367] The catalyst concentration typically is from about 0.1 to about 10 wt . % ([mass of catalyst÷total reaction mass] x 100%) . More typically, the catalyst concentration is from about 0.1 to about 5 wt.%, still more typically from about 0.1 to about 3.0 wt.% and, most typically, from about 0.1 to about 1.5 wt.%. Concentrations greater than about 10 wt.% are difficult to filter. On the other hand, concentrations less than about 0.1 wt.% tend to produce unacceptably low reaction rates.

[00368] The concentration of PMIDA reagent in the feed stream is not critical. Use of a saturated solution of PMIDA reagent in water is preferred, although for ease of operation, the process is also operable at lesser or greater PMIDA reagent concentrations in the feed stream. If catalyst is present in the reaction mixture in a finely divided form, it is preferred to use a concentration of reactants such that all reactants and the N- (phosphonomethyl) glycine product remain in solution so that the catalyst can be recovered for re-use, for example, by filtration. On the other hand, greater concentrations tend to increase reactor through-put. Alternatively, if the catalyst is present as a stationary phase through which the reaction medium and oxygen source are passed, it may be possible to use greater concentrations of reactants such that a portion of the N- (phosphonomethyl) glycine product precipitates.

[00369] Normally, a PMIDA reagent concentration of up to about 50 wt .% ([mass of PMIDA reagent÷total reaction mass] x 100%) may be used (especially at a reaction temperature of from about 20 to about 180⁰C) . Preferably, a PMIDA reagent concentration of up to about 25 wt . % is used (particularly at a reaction temperature of from about 60 to about 150⁰C) . More preferably, a PMIDA reagent concentration of from about 12 to about 18 wt .% is used (particularly at a reaction temperature of from about 100 to about 130⁰C) . PMIDA reagent concentrations below 12 wt . % may be used, but are less economical because a relatively low payload of N- (phosphonomethyl) glycine product is produced in each reactor cycle and more water must be removed and energy used per unit of N- (phosphonomethyl) glycine product produced. Relatively low reaction temperatures (i.e., temperatures less than 100⁰C) often tend to be less advantageous because the solubility of the PMIDA reagent and N- (phosphonomethyl) glycine product are both relatively low at such temperatures .

[00370] The oxygen source for the PMIDA oxidation reaction may be any oxygen-containing gas or a liquid comprising dissolved oxygen. Preferably, the oxygen source is an oxygen- containing gas. As used herein, an "oxygen-containing gas" is any gaseous mixture comprising molecular oxygen which optionally may comprise one or more diluents which are non-reactive with the oxygen or with the reactant or product under the reaction conditions .

[00371] Examples of such gases are air, pure molecular oxygen, or molecular oxygen diluted with helium, argon, nitrogen, or other non-oxidizing gases. For economic reasons, the oxygen source most preferably is air, oxygen-enriched air, or pure molecular oxygen.

[00372] Oxygen may be introduced by any conventional means into the reaction medium in a manner which maintains the dissolved oxygen concentration in the reaction mixture at a desired level. If an oxygen-containing gas is used, it preferably is introduced into the reaction medium in a manner which maximizes the contact of the gas with the reaction solution. Such contact may be obtained, for example, by dispersing the gas through a diffuser such as a porous frit or by stirring, shaking, or other methods known to those skilled in the art.

[00373] The oxygen feed rate preferably is such that the PMIDA oxidation reaction rate is not limited by oxygen supply. Generally, it is preferred to use an oxygen feed rate such that at least about 40% of the oxygen is utilized. More preferably, the oxygen feed rate is such that at least about 60% of the oxygen is utilized. Even more preferably, the oxygen feed rate is such that at least about 80% of the oxygen is utilized. Most preferably, the rate is such that at least about 90% of the oxygen is utilized. As used herein, the percentage of oxygen utilized equals: (the total oxygen consumption rate ÷ oxygen feed rate) x 100%. The term "total oxygen consumption rate" means the sum of: (i) the oxygen consumption rate ("R₁") of the oxidation reaction of the PMIDA reagent to form the N- (phosphonomethyl) glycine product and formaldehyde, (ii) the oxygen consumption rate ("R₁₁") of the oxidation reaction of formaldehyde to form formic acid, and (iii) the oxygen consumption rate ("R₁₁₁") of the oxidation reaction of formic acid to form carbon dioxide and water.

[00374] In various embodiments of this invention, oxygen is fed into the reactor as described above until the bulk of PMIDA reagent has been oxidized, and then a reduced oxygen feed rate is used. This reduced feed rate preferably is used after about 75% of the PMIDA reagent has been consumed. More preferably, the reduced feed rate is used after about 80% of the PMIDA reagent has been consumed. Where oxygen is supplied as pure oxygen or oxygen-enriched air, a reduced feed rate may be achieved by purging the reactor with (non-enriched) air, preferably at a volumetric feed rate which is no greater than the volumetric rate at which the pure molecular oxygen or oxygen-enriched air was fed before the air purge. The reduced oxygen feed rate preferably is maintained for from about 2 to about 40 minutes, more preferably from about 5 to about 20 minutes, and most preferably from about 5 to about 15 minutes. While the oxygen is being fed at the reduced rate, the temperature preferably is maintained at the same temperature or at a temperature less than the temperature at which the reaction was conducted before the air purge. Likewise, the pressure is maintained at the same or at a pressure less than the pressure at which the reaction was conducted before the air purge. Use of a reduced oxygen feed rate near the end of the PMIDA reaction allows the amount of residual formaldehyde present in the reaction solution to be reduced without producing detrimental amounts of AMPA by oxidizing the N- (phosphonomethyl) glycine product .

[00375] In embodiments in which a catalyst mixture comprising a noble metal on carbon catalyst is used, reduced losses of noble metal may be observed with this invention if a sacrificial reducing agent is maintained or introduced into the reaction solution. Suitable reducing agents include formaldehyde, formic acid, and acetaldehyde . Most preferably, formic acid, formaldehyde, or mixtures thereof are used. Experiments conducted in accordance with this invention indicate that if small amounts of formic acid, formaldehyde, or a combination thereof are added to the reaction solution, the catalyst will preferentially effect the oxidation of the formic acid or formaldehyde before it effects the oxidation of the PMIDA reagent, and subsequently will be more active in effecting the oxidation of formic acid and formaldehyde during the PMIDA oxidation. Preferably from about 0.01 to about 5.0 wt . % ([mass of formic acid, formaldehyde, or a combination thereof ÷ total reaction mass] x 100%) of sacrificial reducing agent is added, more preferably from about 0.01 to about 3.0 wt . % of sacrificial reducing agent is added, and most preferably from about 0.01 to about 1.0 wt . % of sacrificial reducing agent is added.

[00376] In certain embodiments, unreacted formaldehyde and formic acid are recycled back into the reaction mixture for use in subsequent cycles. In this instance, an aqueous recycle stream comprising formaldehyde and/or formic acid also may be used to solubilize the PMIDA reagent in the subsequent cycles. Such a recycle stream may be generated by evaporation of water, formaldehyde, and formic acid from the oxidation reaction mixture in order to concentrate and/or crystallize product N- (phosphonomethyl) glycine . Overheads condensate containing formaldehyde and formic acid may be suitable for recycle.

[00377] As noted above, various oxidation catalysts, mixtures, and systems of the present invention comprising one or more metal compositions (e.g., a primary transition metal nitride and/or a secondary metal nitride) are effective for the oxidation of formaldehyde to formic acid, carbon dioxide and water. In particular, catalysts of the present invention are effective for the oxidation of byproduct formaldehyde produced in the oxidation of N- (phosphonomethyl) iminodiacetic acid. More particularly, such catalysts may be characterized by their effectiveness for catalyzing the oxidation of formaldehyde such that when a representative aqueous solution containing about 0.8% by weight formaldehyde and having a pH of about 1.5 is contacted with an oxidizing agent in the presence of the catalyst at a temperature of about 100⁰C, at least about 5%, preferably at least about 10%, more preferably at least about 15%, even more preferably at least about 20% or even at least about 30% by weight of the formaldehyde is converted to formic acid, carbon dioxide and/or water.

[00378] Transition metal catalysts of the present invention are particularly effective in catalyzing the liquid phase oxidation of formaldehyde to formic acid, carbon dioxide and/or water in the presence of a PMIDA reagent such as

N- (phosphonomethyl) iminodiacetic acid. More particularly, such catalysts may be characterized by their effectiveness for catalyzing the oxidation of formaldehyde such that when a representative aqueous solution containing about 0.8% by weight formaldehyde and about 6% by weight of N-

(phosphonomethyl) iminodiacetic acid and having a pH of about 1.5 is contacted with an oxidizing agent in the presence of the catalyst at a temperature of about 100⁰C, at least about 50%, preferably at least about 60%, more preferably at least about 70%, even more preferably at least about 80%, and especially at least about 90% by weight of the formaldehyde is converted to formic acid, carbon dioxide and/or water.

[00379] Typically, the concentration of

N- (phosphonomethyl) glycine in the product mixture may be as great as 40% by weight, or greater. Preferably, the N- (phosphonomethyl) glycine concentration is from about 5 to about 40%, more preferably from about 8 to about 30%, and still more preferably from about 9 to about 15%. Concentrations of formaldehyde in the product mixture are typically less than about 0.5% by weight, more preferably less than about 0.3%, and still more preferably less than about 0.15%. Hydrogen generation

[00380] Modest hydrogen generation may be associated with use of transition metal-containing catalysts detailed herein in PMIDA oxidation. This hydrogen generation can be effectively dealt with using one or more approaches. Hydrogen formation and/or concentration in the reactor is preferably minimized due to its highly flammable and explosive nature. For example, any adverse effect of hydrogen generation can be minimized by dilution of the reactor headspace with nitrogen or carbon dioxide. Alternatives for this purpose include using compressed air as a portion of the oxygen-containing gas introduced as the oxidant for oxidation of the organic substrate, dilution of the headspace with carbon dioxide formed in the oxidation reaction, and recycle into the reactor headspace carbon dioxide formed in a downstream operation, for example, by oxidation of formic acid that has been separated from an oxidation product mixture produced by the catalytic oxidation of PMIDA to glyphosate. Introduction of nitrogen and/or carbon dioxide to the reactor headspace reduces the headspace concentration of hydrogen and oxygen. Use of compressed air as the oxygen-containing gas provides a source of nitrogen which dilutes both the hydrogen and oxygen concentration in the headspace. In accordance with the present invention, it has been discovered that this modest hydrogen generation is not observed in reactions conducted in the presence of mixtures including a transition metal catalyst and a noble metal catalyst. By avoiding the need to for investment of capital to incorporate any of the above-noted strategies in PMIDA oxidation, the absence of hydrogen generation represents a further advantageous feature of the mixtures of the present invention.

[00381] Following the oxidation, the catalyst preferably is subsequently separated by filtration. The N- (phosphonomethyl) glycine product may then be isolated by precipitation, for example, by evaporation of a portion of the water and cooling. In certain embodiments, it should be recognized that the catalyst of this invention (e.g., a catalyst mixture, combination, or component thereof) has the ability to be reused over several cycles. N- (phosphonomethyl) glycine prepared in accordance with the present invention may be further processed in accordance with many well-known methods in the art to produce agronomically acceptable salts of N- (phosphonomethyl) glycine commonly used in herbicidal glyphosate compositions. As used herein, an "agronomically acceptable salt" is defined as a salt which contains a cation (s) that allows agriculturally and economically useful herbicidal activity of an N- (phosphonomethyl) glycine anion. Such a cation may be, for example, an alkali metal cation (e.g., a sodium or potassium ion) , an ammonium ion, an isopropyl ammonium ion, a tetra-alkylammonium ion, a trialkyl sulfonium ion, a protonated primary amine, a protonated secondary amine, or a protonated tertiary amine. A concentrate comprising a salt of N- (phosphonomethyl) glycine in a concentration of, for example, at least 240 gpl, a.e may be prepared. The concentrate may include a surfactant such as, for example, an alkoxylated alkylamine or an alkoxylated etheramine as described, for example, in Zhu et al. International Publication No. WO 2006/034459. The concentrate may also include an alkoxylated alkylamine quaternary surfactant as described, for example, in Zhu et al . International Publication No. WO 2006/034426.

[00382] The present invention is illustrated by the following examples which are merely for the purpose of illustration and not to be regarded as limiting the scope of the invention or the manner in which it may be practiced. Example 1

[00383] This example details the preparation of a carbon- supported iron-containing catalyst precursor.

[00384] A particulate carbon support (10.0 g) designated D1097 having a Langmuir surface area of approximately 1500 m²/g was added to a 1 liter flask containing deionized water (400 ml) to form a carbon support slurry. The D1097 carbon support was supplied to Monsanto by Degussa. The pH of the slurry was approximately 8.0 and its temperature approximately 20⁰C.

[00385] Iron chloride (FeCl₃ ^«6H₂O) (0.489 g) was added to a 100 ml beaker containing deionized water (30 ml) to form a solution. The iron solution was added to the carbon support at a rate of approximately 2 ml/minute over the course of approximately 15 minutes. The pH of the carbon support slurry was maintained at from about 4 to about 4.4 by co-addition of a 0.1% by weight solution of sodium hydroxide (Aldrich Chemical Co., Milwaukee, WI); approximately 5 ml of the 0.1% by weight sodium hydroxide solution was added to the carbon support slurry during addition of the iron solution. The pH of the slurry was monitored using a pH meter (Thermo Orion Model 290) .

[00386] After addition of the iron solution to the carbon support slurry was complete, the resulting mixture was stirred for 30 minutes using a mechanical stirring rod (at 50% output) (IKA-Werke RW16 Basic) ; the pH of the mixture was monitored using the pH meter and maintained at approximately 4.4 by dropwise addition of 0.1% by weight sodium hydroxide or 0.1% by weight HNO₃.

[00387] The mixture was then heated under a nitrogen blanket to 70⁰C at a rate of about 2°C per minute while its pH was maintained at 4.4. Upon reaching 70⁰C, the pH of the mixture was slowly raised by addition of 0.1 % by weight sodium hydroxide (5 ml) according to the following pH profile: the pH was maintained at approximately 5.0 for 10 minutes, increased to 5.5, maintained at 5.5 for approximately 20 minutes at pH 5.5, and stirred for approximately 20 minutes during which time a constant pH of 6.0 was reached.

[00388] The resulting mixture was filtered and washed with a plentiful amount of deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 1.0% by weight iron.

[00389] Iron-containing precursor (5.0 g) was charged into a Hastelloy C tube reactor packed with high temperature insulation material . The reactor was purged with argon introduced to the reactor at a rate of approximately 100 cm³/min at approximately 20⁰C for approximately 15 minutes. A thermocouple was inserted into the center of the reactor for charging the precursor.

[00390] After introduction of the precursor was complete, the temperature of the reactor was increased to approximately 300⁰C over the course of approximately 15 minutes during which time a 10%/90% (v/v) mixture of acetonitrile and argon (Airgas, Inc., Radnor, PA) was introduced to the reactor at a rate of approximately 100 cm³/minute. The temperature of the reactor was then increased to approximately 950⁰C over the course of 30 minutes during which time the 10%/90% (v/v) mixture of acetonitrile and argon flowed through the reactor at a rate of approximately 100 cm³/minute. The reactor was maintained at approximately 950⁰C for approximately 120 minutes. The reactor was cooled to approximately 20⁰C over the course of approximately 90 minutes under a flow of argon at approximately 100 cm³/minute.

[00391] The resulting catalyst contained approximately 1% by weight iron. Example 2

[00392] This example details the use of various noble metal- containing and non-noble metal-containing catalysts in the oxidation of PMIDA to N- (phosphonomethyl) glycine .

[00393] A 0.5% by weight iron-containing catalyst was prepared generally as described in Example 1 using a solution containing iron chloride (FeCl3*6H₂O) (0.245 g) in deionized water (60 ml) that was contacted with the carbon support slurry.

[00394] The 0.5% by weight iron catalyst was used to catalyze the oxidation of PMIDA to glyphosate (curve 6 of Fig. 4) . Its performance was compared to: (1) 2 samples of a 5% platinum, 0.5% iron (5%Pt/0.5%Fe) particulate carbon catalyst prepared in accordance with Ebner et al . , U.S. Patent No. 6,417,133, Samples 1 and 2 (curves 1 and 4, respectively, of Fig. 4); (2) a particulate carbon catalyst prepared in accordance with Chou, U.S. Patent No. 4,696,772 (4,696,772 catalyst) (curve 3 of Fig. 4); (3) a 1% Fe containing catalyst precursor prepared as described in Example 1 using argon (Ar) alone (curve 2 of Fig. 4); and (4) a particulate carbon support having a Langmuir surface area of approximately 1500 m²/g that was treated with acetonitrile in accordance with the procedure set forth above in Example 1 used to prepare the 1% by weight iron catalyst (curve 5 of Fig. 4) .

[00395] In each instance, the PMIDA oxidation was conducted in a 200 ml glass reactor containing a total reaction mass (200 g) that included 5.74% by weight PMIDA (11.48 g) and 0.11% catalyst (0.22 g) . The oxidation was conducted at a temperature of approximately 100⁰C, a pressure of approximately 60 psig, a stir rate of approximately 100 revolutions per minute (rpm) , and an oxygen flow rate of approximately 150 cm³/minute for a run time of approximately 50 minutes. [00396] The maximum CO2 percentage in the exit gas and cumulative CO₂ generated were used as indicators of the degree of oxidation of PMIDA, formaldehyde, and formic acid.

[00397] Fig. 4 shows the percentage of CO₂ in the exit gas during a first reaction cycle using each of the six different catalysts. As shown in Fig. 4, the 0.5% by weight iron catalyst exhibited greater activity than the 4,696, catalyst and exhibited comparable activity as compared to 5%Pt/0.5%Fe catalysts. Also shown in Fig. 4, the acetonitrile-treated carbon support and argon-treated precursor showed little activity. Table 1 shows the CO₂ in the exit gas and cumulative CO₂ generated in the reaction cycle using each of the 6 catalyst samples .

Table 1

[00398] The designation MCN/C used throughout the present specification and examples does not require the presence of a particular transition metal composition. For example, this designation is not limited to compositions comprising molecular species including carbon. Rather, this designation is intended to encompass transition metal compositions including a transition metal and nitrogen (e.g., a transition metal nitride), a transition metal and carbon (e.g., a transition metal carbide) , and/or a transition metal, nitrogen, and carbon (e.g., a transition metal carbide-nitride) . It is currently believed that there is a high probability that molecular species containing both nitrogen and carbon are, in fact, present in catalysts prepared in accordance with the methods detailed in the present specification and examples. There is substantial experimental evidence of the presence of nitride (s) in the transition metal composition comprising cobalt and this evidence is believed to support the conclusion that nitride (s) are present in the transition metal compositions comprising other transition metals as well. With respect to carbon, the belief that carbide (s) are present is based, at least in part, on the presence of a carbon support, the high temperature treatments used to prepare the catalysts, and/or the use of certain carbon- containing heat treatment atmospheres.

[00399] Fig. 5 shows the first cycle CO₂ profiles for the various catalysts prepared generally as described in Example 1. Curve 1 of Fig. 5 corresponds to the first cycle using the 2% Fe catalyst, curve 2 of Fig. 5 corresponds to the first cycle using the 1% Fe catalyst, curve 3 of Fig. 5 corresponds to the first cycle using the 0.75% Fe catalyst, and curve 4 of Fig. 5 corresponds to the first cycle using the 0.5% Fe catalyst. As shown, the catalyst containing 0.5% by weight iron demonstrated the highest activity.

Example 3

[00400] This example details preparation of a carbon- supported cobalt-containing catalyst precursor containing 1% by weight cobalt.

[00401] A particulate carbon support (10.0 g) having a Langmuir surface area of approximately 1500 m²/g was added to a 1 liter flask containing deionized water (400 ml) to form a slurry. The pH of the slurry was approximately 8.0 and the temperature approximately 20⁰C.

[00402] Cobalt chloride (CoCl₂^H₂O) (0.285 g) (Sigma- Aldrich, St. Louis, MO) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution. The cobalt solution was added to the carbon slurry incrementally over the course of 30 minutes (i.e., at a rate of approximately 2 ml/minute). The pH of the carbon slurry was maintained at from about 7.5 to about 8.0 during addition of the cobalt solution by co-addition of a 0.1 wt% solution of sodium hydroxide (Aldrich Chemical Co., Milwaukee, WI) . Approximately 1 ml of 0.1 wt . % sodium hydroxide solution was added to the carbon slurry during addition of the cobalt solution. The pH of the slurry was monitored using a pH meter (Thermo Orion, Model 290) .

[00403] After addition of the cobalt solution to the carbon slurry was complete, the resulting mixture was stirred using a mechanical stirring rod operating at 50% of output (Model IKA- Werke RW16 Basic) for approximately 30 minutes; the pH of the mixture was monitored using the pH meter and maintained at about 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide (1 ml) or 0.1 wt . % HNO3 (1 ml) . The mixture was then heated under a nitrogen blanket to approximately 45°C at a rate of approximately 2°C per minute while maintaining the pH at approximately 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide (1 ml) or 0.1 wt . % HNO₃ (1 ml). Upon reaching 45°C, the mixture was stirred using the mechanical stirring bar described above for approximately 20 minutes at constant temperature of approximately 45°C and a pH of approximately 8.0. The mixture was then heated to approximately 50⁰C and its pH was adjusted to approximately 8.5 by addition of 0.1 wt . % sodium hydroxide solution (5 ml) ; the mixture was maintained at these conditions for approximately 20 minutes. The mixture was then heated to approximately 60⁰C, its pH adjusted to approximately 9.0 by addition of 0.1 wt . % sodium hydroxide solution (5 ml) and maintained at these conditions for approximately 10 minutes.

[00404] The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at 120⁰C. The precursor contained approximately 1.0% by weight cobalt.

[00405] Catalyst precursor (5.0 g) was charged into a Hastelloy C tube reactor packed with high temperature insulation material . The reactor was purged with argon introduced to the reactor at a rate of approximately 100 cm³/min at approximately 20⁰C for approximately 15 minutes. A thermocouple was inserted into the center of the reactor for charging the precursor.

[00406] After the precursor was charged to the reactor, the temperature of the reactor was raised to approximately 700⁰C during which time a 50%/50% (v/v) hydrogen/methane mixture (Airgas, Inc., Radnor, PA) was introduced to the reactor at a rate of approximately 20 cm³/minute; a flow of argon at a rate of approximately 100 cm³/min was also introduced to the reactor. The reactor was maintained at approximately 700⁰C for approximately 120 minutes.

[00407] The reactor was cooled to approximately 20⁰C over the course of 90 minutes under a flow of argon at approximately 100 cm³/minute. The resulting catalyst contained approximately 1% by weight cobalt.

[00408] A 1% cobalt-containing catalyst was also prepared generally as described in Example 1 (i.e., using acetonitrile) .

Example 4

[00409] Catalysts of varying cobalt loadings (0.75%, 1%, 1.5%, and 2%) prepared generally as described in Example 3 were tested in PMIDA oxidation. [00410] The 1% cobalt-containing catalyst was prepared as described in Example 3 using acetonitrile .

[00411] The precursors of the 0.5%, 0.75%, and 2% by weight cobalt catalysts were prepared in accordance with the procedure set forth above in Example 3 using varying amounts of cobalt chloride (C0CI₂ '2H₂O) , depending on the desired catalyst loading. The catalysts were then prepared in accordance with the procedure described in Example 3 using acetonitrile.

[00412] For the catalyst containing 0.75% by weight cobalt, a solution containing cobalt chloride (0.214 g) in deionized water (60 ml) was prepared and contacted with the carbon support slurry .

[00413] For the catalyst containing 1.5% by weight cobalt, a solution containing cobalt chloride (0.428 g) in deionized water (60 ml) was prepared and contacted with the carbon support slurry .

[00414] For the catalyst containing 2.0% by weight cobalt, a solution containing cobalt chloride (0.570 g) was prepared and contacted with the carbon support slurry.

[00415] Each of the catalysts was tested in PMIDA oxidation under the conditions described in Example 2.

[00416] Fig. 6 shows the first cycle CO₂ profiles using the various catalysts. Curve 1 of Fig. 6 corresponds to the first cycle using the 0.75% Co catalyst, curve 2 of Fig. 6 corresponds to the first cycle using the 1% Co catalyst, curve 3 of Fig. 6 corresponds to the first cycle using the 1.50% Co catalyst, and curve 4 of Fig. 6 corresponds to the first cycle using the 2.0% Co catalyst.

[00417] As shown in Fig. 6, catalysts containing from 1-1.5% cobalt demonstrated the highest activity.

[00418] For comparison purposes, a catalyst containing 5% platinum and 0.5% iron on a carbon support (i.e., 5%Pt/0.5%Fe/C) prepared generally as described in Ebner et al., U.S. Patent No. 6,417,133, was tested in PMIDA oxidation under the conditions described in Example 2.

[00419] The HPLC results for the product streams of the four PMIDA reaction cycles using the 1% cobalt catalyst are shown in Table 2. The HPLC results for the first, second, fourth, and sixth reaction cycles using the 5%Pt/0.5%Fe/C catalyst are summarized in Table 2. The table shows the N- (phosphonomethyl) iminodiacetic acid (GI), N-

(phosphonomethyl) glycine (GIy), formaldehyde (FM), formic acid (FA) , iminodiacetic acid (IDA) , aminomethylphosphonic acid and methyl aminomethylphosphonic acid ((M)AMPA), N-methy-N- (phosphonomethyl) glycine (NMG), imino-bis- (methylene) -bis- phosphonic acid (iminobis) , and phosphate ion (PO₄) content of the reaction mixture for the various cycles.

Example 5

[00420] Figs. 7-10 provide reaction testing results for catalysts prepared generally as described above.

[00421] Fig. 7 shows the CO₂ percentage in the exit gas during each of four reaction cycles (labeled accordingly) carried out using a 1% iron catalyst.

[00422] Fig. 8 shows the CO₂ percentage in the exit gas during each of four reaction cycles (labeled accordingly) carried out using a 1% cobalt catalyst.

[00423] Fig. 9 shows the CO₂ percentage in the exit gas during each of six reaction cycles (labeled accordingly) carried out using a 5%Pt/0.5%Fe/C catalyst.

[00424] Fig. 10 shows the CO₂ percentage in the exit gas during each of two reaction cycles (labeled accordingly) carried out using a 4,696,772 catalyst.

Example 6

[00425] This example details the preparation of various carbon-supported metal-containing catalysts.

[00426] Precursors containing vanadium, tellurium, molybdenum, tungsten, ruthenium, and cerium were prepared generally in accordance with Example 1 with variations in the pH and heating schedule depending on the metal to be deposited (detailed below) .

[00427] Preparation of vanadium precursor: Na₃VO₄»10H₂O (0.721 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the vanadium solution, the pH of the carbon support slurry was maintained at from about 3.4 to about 3.7 by co-addition of a 0.1 wt . % solution of nitric acid. Approximately 5 ml of nitric acid was added to the carbon support slurry during addition of the vanadium solution. After addition of the vanadium solution to the carbon support slurry was complete, the resulting mixture was stirred for 30 minutes using mechanical stirring rod operating at 50% of output (Model IKA-Werke RW16 Basic) with the pH of the mixture monitored using the pH meter described above and maintained at approximately 3.6 by addition of nitric acid (0.1 wt .% solution) (2 ml) . The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 1% by weight vanadium.

[00428] Preparation of tellurium precursor: Te(OH)₆ (0.092 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the tellurium solution, the pH of the carbon support slurry was maintained at from about 6.5 to about 6.9 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 2 ml of 0.1 wt . % sodium hydroxide solution was added to the carbon support slurry during addition of the tellurium solution. After addition of the tellurium solution to the carbon support slurry was complete, the resulting mixture was stirred for 30 minutes with the pH of the mixture monitored using the pH meter described above and maintained at approximately 6.7 by addition of 0.1 wt . % sodium hydroxide solution (1-2 ml) . The pH of the mixture was maintained at pHs of 6.0, 5.0, 4.0, 3.0, 2.0, and 1.0 for 10 minutes each. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 1% by weight tellurium.

[00429] Preparation of molybdenum precursor: (NH₄) ₂Mo0₄ (0.207 g) was added to a 100 ml beaker containing deionized water (50 ml) to form a solution that was contacted with the carbon support slurry. During addition of the molybdenum solution, the pH of the carbon support slurry was maintained at from about 1.5 to about 2.0 by co-addition of a 0.1 wt . % solution of nitric acid. Approximately 5 ml of the 0.1 wt . % nitric acid solution was added to the carbon support slurry during addition of the molybdenum solution. After addition of the molybdenum solution to the carbon slurry was complete, the resulting mixture was stirred for approximately 30 minutes with pH of the slurry monitored using the pH meter and maintained at approximately 2.0 by addition of 0.1 wt . % nitric acid. The pH was then increased to approximately 3.0 by addition of 0.1 wt . % sodium hydroxide, maintained at approximately 3.0 for approximately 20 minutes, increased to approximately 4.0 by addition of 0.1 wt . % sodium hydroxide solution, and maintained at approximately 4.0 for approximately 20 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight molybdenum.

[00430] Preparation of tungsten precursor: (NH₄) ₆Wi₂O₃₉»2H₂O (0.135 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the tungsten solution, the pH of the carbon support slurry was maintained at from about 3.0 to about 3.2 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 2 ml of nitric acid was added to the carbon support slurry during addition of the tungsten solution. After addition of the tungsten solution to the carbon support slurry, the resulting mixture was stirred for approximately 30 minutes with pH of the mixture monitored using the pH meter described above and maintained at approximately 3.0 by addition of 0.1 wt . % nitric acid solution. The pH of the mixture was then decreased to approximately 2.5 by addition of 0.1 wt .% nitric acid solution, maintained at approximately 2.5 for 10 minutes, decreased to approximately 2.0 by addition of 0.1 wt . % nitric acid solution, and maintained at approximately 2.0 for 10 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight tungsten.

[00431] Preparation of ruthenium precursor: RuCl₃»2H₂O (0.243 g) was added to a 100 ml beaker containing deionized water (50 ml) to form a solution that was contacted with the carbon support slurry. During addition of the ruthenium solution, the pH of the carbon support slurry was maintained at from about 3.0 to about 3.5 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 1 ml of sodium hydroxide was added to the carbon support slurry during addition of the ruthenium solution. After addition of the ruthenium solution to the carbon support slurry was complete, the resulting mixture was stirred for approximately 30 minutes with the pH of the mixture monitored using the pH meter (described above) and maintained at approximately 3.5 by addition of 0.1 wt . % nitric acid solution. The pH of the mixture was then increased to approximately 4.2 by addition of 0.1 wt . % sodium hydroxide (1 ml), maintained at approximately 4.2 for approximately 10 minutes, increased to approximately 5.0 by addition of 0.1 wt . % sodium hydroxide solution (1 ml), maintained at approximately 5.0 for approximately 10 minutes, increased to approximately 5.7 by addition of 0.1 wt . % sodium hydroxide (1 ml), and maintained at approximately 5.7 for approximately 10 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 1% by weight ruthenium. [00432] Preparation of cerium precursor: Ce (NO₃) 3*6H₂O (0.117 g) was added to a 100 ml beaker containing deionized water (50 ml) to form a solution that was contacted with the carbon support slurry. During addition of the cerium solution, the pH of the carbon support slurry was maintained at from about 7.0 to about 7.5 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 1 ml of sodium hydroxide was added to the carbon support slurry during addition of the cerium solution. After addition of the cerium solution to the carbon support slurry was complete, the resulting mixture was stirred for approximately 30 minutes with pH of the slurry monitored using the pH meter and maintained at approximately 7.5 by addition of 0.1 wt . % sodium hydroxide solution (1 ml) . The pH was then increased to approximately 8.0 by addition of 0.1 wt . % sodium hydroxide (1 ml), maintained at approximately 8.0 for 20 minutes, increased to approximately 9.0 by addition of 0.1 wt . % sodium hydroxide (1 ml), maintained at approximately 9.0 for 20 minutes, increased to approximately 10.0 by addition of 0.1 wt . % sodium hydroxide solution (1 ml), and maintained at approximately 10.0 for 20 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight cerium.

[00433] Precursors were also prepared for catalysts containing nickel, chromium, manganese, magnesium, copper, and silver generally in accordance with Example 3 detailing preparation of a cobalt-containing catalyst precursor with variations in the pH and heating schedule depending on the metal to be deposited (described below) .

[00434] Preparation of nickel precursor: NiCl₂»6H₂O (0.409 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the nickel solution, the pH of the carbon support slurry was maintained at from about 7.5 to about 8.0 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 2 ml of sodium hydroxide was added to the carbon support slurry during addition of the nickel solution. After addition of the nickel solution to the carbon support slurry, the resulting mixture was stirred for approximately 30 minutes with pH of the slurry monitored using the pH meter described above and maintained at approximately 8.0 by addition of 0.1 wt . % sodium hydroxide solution (1 ml) . The mixture was then heated under a nitrogen blanket to approximately 40⁰C at a rate of about 2°C per minute while maintaining its pH at approximately 8.5 by addition of 0.1 wt . % sodium hydroxide solution. Upon reaching approximately 60⁰C, the mixture was stirred for approximately 20 minutes at constant temperature of approximately 40⁰C and a pH of approximately 8.5. The mixture was then heated to approximately 50⁰C and its pH was adjusted to approximately 9.0 by addition of sodium hydroxide solution (2 ml) ; the mixture was maintained at these conditions for approximately 20 minutes. The mixture was then heated to approximately 60⁰C, its pH adjusted to approximately 10.0 by addition of sodium hydroxide solution (2 ml) and maintained at these conditions for approximately 20 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight nickel.

[00435] Preparation of chromium precursor: CrCl₃»6H₂O (0.517 g) was added to a 100 ml beaker containing deionized water (50 ml) to form a solution which was contacted with the carbon support slurry. During addition of the chromium solution, the pH of the carbon support slurry was maintained at from about 7.0 to about 7.5 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 1 ml of sodium hydroxide was added to the carbon support slurry during addition of the chromium solution. After addition of the chromium solution to the carbon support slurry was complete, the resulting mixture was stirred for approximately 30 minutes with pH of the mixture monitored using the pH meter described above and maintained at approximately 7.5 by addition of sodium hydroxide. The mixture was then heated under a nitrogen blanket to approximately 60⁰C at a rate of about 2°C per minute while maintaining its pH at approximately 8.0 by addition of 2 ml of 0.1 wt . % sodium hydroxide. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight chromium.

[00436] Preparation of manganese precursor: MnCl₂MH₂O (0.363 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the manganese solution, the pH of the carbon support slurry was maintained at from about 7.5 to about 8.0 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 1 ml of sodium hydroxide solution was added to the carbon support slurry during addition of the manganese solution. After addition of the manganese solution to the carbon support slurry was complete, the resulting mixture was stirred for approximately 30 minutes with pH of the mixture monitored using the pH meter described above and maintained at approximately 7.4 by addition of sodium hydroxide. The mixture was then heated under a nitrogen blanket to approximately 45°C at a rate of about 2°C per minute while maintaining its pH at approximately 8.0 by addition of 2 ml of 0.1 wt . % sodium hydroxide solution. Upon reaching approximately 60⁰C, the mixture was stirred for approximately 20 minutes at constant temperature of approximately 50⁰C and a pH of approximately 8.5. The mixture was then heated to approximately 55°C and its pH was adjusted to approximately 9.0 by addition of sodium hydroxide solution (2 ml); the mixture was maintained at these conditions for approximately 20 minutes. The mixture was then heated to approximately 60⁰C, its pH adjusted to approximately 9.0 by addition of sodium hydroxide solution (1 ml) and maintained at these conditions for approximately 20 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120 ⁰C. The precursor contained approximately 1% by weight manganese.

[00437] Preparation of magnesium precursor: MgCl₂*6H₂O (0.420 g) was added to a 100 ml beaker containing deionized water (50 ml) to form a solution that was contacted with the carbon support slurry. During addition of the magnesium solution, the pH of the carbon support slurry was maintained at from about 8.5 to about 9.0 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 5 ml of sodium hydroxide solution was added to the carbon support slurry during addition of the magnesium solution. After addition of the magnesium solution to the carbon slurry was complete, the resulting mixture was stirred for 30 minutes with pH of the mixture monitored using the pH meter and maintained at approximately 8.5 by addition of 0.1 wt . % sodium hydroxide solution (1 ml) . The pH of the mixture was then increased to approximately 9.0 by addition of 0.1 wt . % sodium hydroxide solution (1 ml) and maintained at approximately 9.0 for approximately 30 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at 120 ⁰C. The precursor contained approximately 1% by weight magnesium.

[00438] Preparation of copper precursor: CuCl₂ (1.11 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the copper solution, the pH of the carbon support slurry was maintained at from about 6.0 to about 6.5 by co-addition of a 0.1 wt . % solution of sodium hydroxide. Approximately 1 ml of sodium hydroxide was added to the carbon slurry during addition of the copper solution. After addition of the copper solution to the carbon slurry was complete, the slurry was stirred for approximately 30 minutes with pH of the slurry monitored using the pH meter and maintained at approximately 6.5 by addition of sodium hydroxide. The slurry was then heated under a nitrogen blanket to approximately 40⁰C at a rate of about 2°C per minute while maintaining its pH at approximately 7.0 by addition of 0.1 wt . % sodium hydroxide solution. Upon reaching approximately 40⁰C, the slurry was stirred for approximately 20 minutes at constant temperature of approximately 40⁰C and a pH of approximately 7.0. The slurry was then heated to approximately 50⁰C and its pH was adjusted to approximately 7.5 by addition of approximately 0.1 wt . % sodium hydroxide solution (1 ml) ; the slurry was maintained at these conditions for approximately 20 minutes. The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 5% by weight copper.

[00439] Preparation of silver precursor: AgNC>₃ (0.159 g) was added to a 100 ml beaker containing deionized water (60 ml) to form a solution that was contacted with the carbon support slurry. During addition of the silver solution, the pH of the carbon support slurry was maintained at from about 4.0 to about 4.5 by co-addition of a 0.1 wt . % solution of nitric acid. Approximately 2 ml of nitric acid solution was added to the carbon slurry during addition of the silver solution. After addition of the silver solution to the carbon support slurry was complete, the resulting mixture was stirred for approximately 30 minutes with pH of the mixture monitored using the pH meter and maintained at approximately 4.5 by addition of nitric acid solution (2 ml) . The resulting mixture was filtered and washed with deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C. The precursor contained approximately 1% by weight silver. Metal (M), nitrogen and carbon-containing catalysts (MCN/C) containing 1% by weight metal (in the case of copper, 5% by weight) were prepared from each of the catalyst precursors as described above in Example 1.

Example 7

[00440] Each of the catalysts prepared as described in Example 6 was tested in PMIDA oxidation under the conditions described in Example 2.

[00441] The maximum CO₂ percent composition in the exit gas and the total CO₂ generated during the 50 minutes of reaction were used to measure the catalysts' activity. The results are shown in Table 3.

[00442] The carbon-supported cobalt-containing catalyst and chromium-containing catalysts showed the highest PMIDA oxidation activity .

Example 8

[00443] This example details the effectiveness of various carbon-supported carbide-nitride containing catalysts for the oxidation of formaldehyde and formic acid during PMIDA oxidation under the conditions described in Example 2.

[00444] Two methods were employed to evaluate the activity of various carbon-supported metal carbide-nitride catalysts in the oxidation of formaldehyde and formic acid: (1) HPLC analysis of the reaction product and (2) the CO₂ drop-point measurement. The drop-point measurement is the total amount of CO₂ that has passed through the exit gas at the moment a sudden reduction in exit gas CO₂ composition is observed. As shown in Fig. 11, a particulate carbon catalyst containing 5%Pt/l% Fe prepared in accordance with U.S. Patent No. 6,417,133 to Ebner et al . produces a CO₂ drop-point around 1500-1600 cm³ of total CO₂ under the PMIDA oxidation conditions of Example 10 (curve 1 of Fig. 11) . Also shown in Fig. 11, a 1% cobalt-containing catalyst prepared as described above in Example 3 using acetonitrile, exhibits a CO₂ drop point around 1300 cm³ under the PMIDA oxidation conditions of Example 2 (curve 2 of Fig. 11) .

[00445] The approximately 200-300 cm³ increase in total CO₂ generation associated with use of the 5%Pt/l% Fe catalyst prepared in accordance with U.S. Patent No. 6,417,133 to Ebner et al . may be due to greater oxidation of formic acid as compared to the 1% cobalt catalyst.

[00446] Table 4 shows the HPLC results of the PMIDA oxidation product using various carbon-supported carbide-nitride catalysts prepared as described above in Example 7 : 1% by weight cobalt, 1% by weight manganese, 5% by weight copper, 1% by weight magnesium, 1% by weight chromium, 1% by weight molybdenum, and 1% by weight tungsten. The carbon-supported cobalt carbide-nitride catalyst showed the highest formaldehyde oxidation activity. Table 4

[00447] Catalyst mixtures (0.2Ig) containing 50% by weight of the 1% by weight cobalt catalyst prepared as described in Example 3 using acetonitrile and 50% by weight of each of the 1% nickel, 1% vanadium, 1% magnesium, and 1% tellurium catalysts prepared in accordance with Example 7 were prepared and tested under the PMIDA oxidation conditions described in Example 2 to further test the activity toward oxidation of formaldehyde and formic acid. A drop point of approximately 1300 cm³ was observed for each of the 4 catalyst mixtures .

Example 9

[00448] This example details use of various promoters in combination with a 1% cobalt catalyst prepared as described above in Example 3 using acetonitrile in PMIDA oxidation under the conditions described in Example 2. The 1% cobalt catalyst loading was 0.021 g.

[00449] The promoters tested were: bismuth nitrate (Bi (NO₃) ₃), bismuth oxide (Bi₂O₃), tellurium oxide (TeO₂), iron chloride (FeCl₃) , nickel chloride (NiCl₂) , copper sulfate (CuSO₄), ammonium molybdate ( (NH₄) 2MoO₄) , and ammonium tungstate ( (NH₄) _I0Wi₂O_4I) . The promoters were introduced to the reaction mixture at the outset of the reaction cycle. The promoters were introduced to the reaction mixture at varying loadings as shown in Table 5.

[00450] The maximum CO₂ concentration in the exit gas stream and the cumulative CO₂ number were measured to determine the catalytic activity and the CO₂ drop-point measurement was recorded to determine the catalytic formic acid oxidation activity. Table 5 shows the maximum CO₂ in the exit gas and the total CO₂ generated during a first 50 minute reaction cycle. The CO₂ drop points when using each of the six promoters were between about 1300 and 1350 cm³. It is recognized that certain of these promoters qualify as secondary catalysts as described above or, if not, may provide an auxiliary effect for oxidation of one or more substrates (e.g., PMIDA, formaldehyde and/or formic acid) .

Table 5

Example 10

[00451] This Example provides reaction testing results for 1.5% and 1% cobalt catalysts prepared generally as described above .

[00452] As shown in Fig. 12, the 1.5% cobalt catalyst had lower activity than the 1% cobalt catalyst but exhibited greater stability.

Example 11

[00453] This example details use of a 1:1 mixture (0.21 g) of a 5%Pt/0.5%Fe catalyst prepared in accordance with U.S. Patent No. 6,417,133 to Ebner et al . (0.105 g) and a carbon- supported catalyst containing 1% by weight cobalt prepared as described above in Example 3 using acetonitrile (0.105 g) in PMIDA oxidation. The catalyst mixture was tested in PMIDA oxidation under the conditions set forth in Example 2 over the course of six reaction cycles.

[00454] For comparison purposes, a 5%Pt/0.5%Fe catalyst prepared in accordance with U.S. Patent No. 6,417,133 to Ebner et al . (0.21 g) was also tested in PMIDA oxidation under the conditions set forth in Example 2 over the course of six reaction cycles.

[00455] The maximum CO₂ proportion in the exit gas, total CO₂ generated during each of the reaction cycles, remaining formaldehyde content in the reaction mixture, formic acid content in the reaction mixture, and platinum leaching are summarized below in Table 6.

Table 6

[00456] The catalyst mixture performed similarly to the 5%Pt/0.5%Fe catalyst in the first cycle except the catalyst mixture exhibited a lower cumulative CO₂ number, possibly due to less oxidation of formic acid. During the remaining cycles, the catalyst mixture performed in a similar manner to the 1% by weight cobalt catalyst (based on the results set forth in, for example, Example 4) and exhibited deactivation with the accumulation of formic acid. Metal analysis showed minimal Pt leaching, indicating the platinum had been deactivated.

Example 12

[00457] Various carbon-supported cobalt carbide-nitride catalysts were prepared in accordance with the process described above in Example 3 generally by varying the atmosphere introduced to the reactor.

[00458] Methane/hydrogen reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a methane/hydrogen environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 100 cm³/minute of a 50%/50% (v/v) mixture of methane and hydrogen.

[00459] Ammonia reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under an ammonia environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 50 cm³/minute NH₃ and 100 cm³/minute of argon .

[00460] Ammonia reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under an ammonia environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 50 cm³/minute NH₃, 20 cm³/minute hydrogen, and 100 cm³/minute of argon.

[00461] Ammonia/methane reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under an NH₃/CH₄ environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 25 cm³/minute NH₃, 25 cm³/minute of a 50%/50% (v/v/) mixture of hydrogen/methane, and 100 cm³/minute of argon . [00462] Acetonitrile reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under an acetonitrile-containing environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 100 cm³/minute argon and approximately 10 cm³/minute of acetonitrile vapor.

[00463] Butylamine reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a butylamine-containing environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 100 cm³/minute argon and approximately 15 cm³/minute of butylamine vapor.

[00464] Pyridine reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a pyridine-containing environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 100 cm³/minute argon and approximately 3 cm³/minute of pyridine vapor.

[00465] Pyrrole reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a pyrrole- containing environment; catalyst precursor (5.0 g) was treated in the reactor using a flow of 100 cm³/minute argon and approximately 2 cm³/minute of pyrrole vapor.

[00466] Picolonitrile reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a picolonitrile-containing environment; catalyst precursor (5.0 g) and picolonitrile (3 g) were treated in the reactor using a flow of 100 cm³/minute argon.

[00467] Melamine reactor environment: A 1% by weight cobalt catalyst was prepared as described in Example 3 under a melamine-containing environment; catalyst precursor (5.0 g) and melamine (1 g) were treated in the reactor using a flow of 100 cm³/minute argon.

[00468] A carbon-supported cobalt containing catalyst was prepared using an organometallic compound (cobalt (II) phthalocyanine) . A particulate carbon support (5.0 g) having a Langmuir surface area of approximately 1500 m²/g and acetone (200 ml) (Aldrich, Milwaukee, WI) were added to a 1 liter flask to form a slurry. Cobalt (II) phthalocyanine (0.490 g) was dissolved in acetone (200 ml) contained in a 1 liter flask. The cobalt-containing solution was added to the carbon support slurry over the course of approximately 30 to 40 minutes. The resulting mixture was stirred using a mechanical stirring rod at 50% output at approximately 20⁰C for approximately 48 hours under a nitrogen blanket. The mixture was filtered and dried in a vacuum oven for approximately 16 hours at approximately 120⁰C under a small nitrogen flow of approximately 20 cm³/minute. The resulting precursor contained approximately 1% by weight cobalt. Dried catalyst precursor (5.0 g) was charged to the Hastelloy C tube reactor described in Example 1 via a thermocouple inserted into the center of the reactor. The reactor was purged with argon introduced at a rate of approximately 100 cm³/minute at approximately 20⁰C for approximately 15 minutes. After the precursor was charged to the reactor, the temperature of the reactor was increased to approximately 950⁰C over the course of approximately 45 minutes under a flow of argon of 100 cc/min. The temperature of the reactor was maintained at approximately 950⁰C for approximately 120 minutes. The resulting catalyst contained approximately 1% by weight cobalt.

Example 13

[00469] This example details the results of PMIDA oxidations carried out under the conditions described in Example 2 using each of the catalysts prepared as described in Example 12. The results are shown in Table 7. Table 7

[00470] As shown in Table 7, catalysts prepared using CH₄/H₂, NH₃, NH₃ and H₂, and CH₄/H₂ and NH₃ exhibited lower activity as compared to catalysts made from CH₃CN, butylamine, pyridine, pyrrole, picolinonitrile, melamine, and cobalt phthalocyanine. Each cobalt catalyst exhibited formaldehyde oxidation activity when the reaction was driven to greater than 80% PMIDA conversion.

Example 14

[00471] This example details preparation of cobalt- containing catalysts having varying metal loadings and their use in PMIDA oxidation.

[00472] Each catalyst was prepared using an acetonitrile environment in accordance with the procedure set forth above in Example 12 and tested in PMIDA oxidation under the conditions described in Example 2. The results are shown in Table 8. Table 8

[00473] As shown in Table 8, all carbon-supported cobalt carbide-nitride catalysts exhibited good PMIDA oxidation activity. The catalysts also demonstrated higher formaldehyde oxidation activity and much better stability compared to the carbon-supported iron carbide-nitride catalyst. The carbon- supported cobalt carbide-nitride catalyst containing 1-2% by weight cobalt exhibited the best overall reaction performance.

Example 15

[00474] Various carbon-supported transition metal-containing catalysts and carbon supports were analyzed to determine their total Langmuir surface area, Langmuir surface area attributed to pores having a diameter less than 2OA (i.e., micropores), and Langmuir surface area attributed to pores having a diameter greater than 2OA (i.e., mesopores and micropores) . The surface area and pore volume analyses were carried out using a Micromeritics 2010 Micropore analyzer with a one-torr transducer and a Micromeritics 2020 Accelerated Surface Area and Porosimetry System, also with a one-torr transducer. These analysis methods are described in, for example, Analytical Methods in fine Particle Technology, First Edition, 1997, Micromeritics Instrument Corp.; Atlanta, Georgia (USA); and Principles and Practice of Heterogeneous Catalysis, 1997, VCH Publishers, Inc; New York, NY (USA) .

[00475] Catalysts and supports analyzed included: the carbon support described above in Example 1 having a total Langmuir surface area of approximately 1500 m²/g, a l%FeCN/C catalyst prepared in accordance with Example 1, a 1% CoCN/C catalyst prepared in accordance with Example 3, a carbon support having a total Langmuir surface area of approximately 1600 m²/g, and a 1.1% FeTPP/C catalyst prepared in accordance with Coleman et al., International Publication No. WO 03/068387 Al. The results are shown in Table 9.

Table 9

[00476] Fig. 13 shows a comparison of the pore surface area of the of the 1% Fe, 1% Co catalysts, and the carbon support. Fig. 14 compares the pore surface area of the 1.1% FeTPP catalyst and its carbon support. As shown in Fig. 13, the 1% Fe catalyst has a surface area approximately 80% the total surface area of its carbon support while the 1% Co catalyst has a surface area approximately 72% the total surface area of its carbon support. As shown in Fig. 14, the 1.1% FeTPP catalyst has a surface area approximately 55% of the total surface area of its carbon support.

Example 16

[00477] 1% CoCN/C and 1.5% CoCN/C catalysts prepared as described in Example 4 were analyzed by Inductively Coupled Plasma (ICP) analysis to determine their nitrogen and transition metal contents. The analysis was carried out using a Thermo Jarrell Ash (TJA) , IRIS Advantage Duo View inductively coupled plasma optical emission spectrometer. The results are shown in Table 10. Table 10

Example 17

[00478] This example details X-ray powder diffraction (XRD) analysis of various catalysts prepared under different conditions. The catalysts were generally prepared in accordance with the procedures set forth above. The samples and conditions for their preparation are described below in Table 11.

[00479] The powder samples were analyzed by placing them directly onto a zero background holder and then placing them directly into a Philips PW 1800 Θ/Θ diffractometer using Cu radiation at 40 KV/30mA and equipped with a diffracted beam monochromator to remove the floursecent radiation from the cobalt .

[00480] The resulting diffraction patterns for samples 1-8 are shown in Figs. 15-22, respectively. The diffraction patterns for samples 1-4, and 6 (Figs. 15-18, and 20) detected graphite and the face centered cubic (FCC) form of cobalt. Particle size analysis of the cobalt and graphite phases was performed through broadening of the diffraction lines which is sensitive to particles in the 100 A to 2000 A range. The results are summarized below in Table 12.

Table 12

[00481] The diffraction patterns for sample 7 (Fig. 21) detected graphite and iron carbide (Fe₃C) . Particle size analysis provided a particle size of the graphite of >1000 A and approximately 505 A. The diffraction patterns for sample 8 (Fig. 22) detected graphite, chromium nitride (CrN), iron nitide (FeN) , chromium, and iron carbide (Fe₃C) . Particle size analysis provided a particle size of graphite of approximately 124 A, chromium nitride of approximately 183 A, and iron nitride of approximately 210 A.

[00482] Quantitative analysis was carried out on Samples 1 and 2. The preferred internal standard was ZnO since it is well characterized and has no lines that overlap the peaks of interest. Approximately 100 mg of samples 1 and 2 were mixed with 10.7% ZnO (Sample 1) and 4.89% ZnO (Sample 2) and tested using the XRD procedure described above. The resulting diffraction for patterns for Samples 1 and 2 are provided in Figs. 23 and 24, respectively.

[00483] Quantitative analysis was then carried out on Samples 1 and 2 using Rivetfeld refinement to determine the amount of each phase. The Rivetfeld refinement is a whole pattern-fitting program that computes a diffraction pattern based on first principles, compares it to the experimental pattern, computes an error between the two patterns, and then modifies the theoretical pattern until the residual error is minimized. In both cases, the Rivetfeld refinement gave low residual errors in the 5-7% range. The results of the Rivetfeld refinement are set forth below in Table 13.

[00484] An estimate of the weight fractions of Samples 3 and 6 are provided in Table 14.

[00485] Figs. 25 and 26 provide comparisons of the diffraction patterns of Samples 2 and 3, and Samples 3 and 6, respectively .

Example 18

[00486] This example details scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis of Samples 1, 2, 4, 7, and 8 described above in Example 17. The SEM analysis was performed using a JEOL (JEOL USA, Peabody, MA) JSM 6460LV scanning electron microscope operated at 3OkV. The TEM characterizations were carried out using a JEOL 1200 EX transmission electron microscope operated at 120 keV and/or JEOL 2000 EX TEM operated at 200 keV.

[00487] Figs. 27 and 28 are SEM images showing a view of the powder of Sample 1 and a cross-sectional view, respectively. Figs. 29 and 30 are SEM images showing the distribution of carbon nanotubes on the surface of the carbon substrate and the morphology of the carbon nanotubes, respectively. Figs. 31 and 32 are SEM images showing the carbon nanoutubes of the powder sample of Sample 1.

[00488] Figs. 33 and 34 are SEM images showing a view of the powder of Sample 2 and a cross-sectional view, respectively. Figs. 35 and 36 are SEM images showing the distribution of the cobalt particles on the powder sample of Sample 2 and cross- sectional view, respectively. Fig. 37 is an SEM image showing the carbon nanotubes on the surface of the carbon support. Fig. 38 is an Energy dispersive X-ray analysis spectroscopy (EDS) spectrum of the powder sample of Sample 2. The EDS spectrum of Sample 2 was determined using an Oxford energy dispersive X-ray spectroscopy system.

[00489] Figs. 39 and 40 are TEM image images of Sample 4 at low and high magnification, respectively. Fig. 41 is an SEM image of a powder sample of Sample 7. Fig. 42 is a backscattered electron image of the powder sample of Sample 7.

[00490] Figs. 43 and 44 are TEM images showing a cross- sectional view of Sample 7.

[00491] Fig. 45 is an SEM image of a powder sample of Sample 8. Fig. 46 is a backscattered electron image of the powder sample of Sample 8. Figs. 47 and 48 are high magnification SEM images of powder sample 8 showing the growth of carbon nanotubes on the carbon support. Figs. 49 and 50 are TEM images providing a cross-sectional view of Sample 8. Example 19

[00492] This examples details X-ray Photoelectron Spectroscopy Analysis (XPS) of the samples described above in Example 17 (detailed in Table 11) .

[00493] The XPS analysis was performed under the analytical conditions set forth in Table 15.

Table 15

[00494] Surface concentration results (area comment) for Samples 1-6 in terms of Atomic % and Weight % are detailed below in Tables 16 and 17, respectively. The spectra are set forth in Figs. 51 and 52.

Table 16

Table 17

Example 20

[00495] This example details preparation of a carbon- supported cobalt and titanium-containing catalyst precursor containing 1% by weight cobalt and 1% by weight titanium.

[00496] Add a particulate carbon support containing 1% by weight titanium prepared as described above in Example 33 (10.0 g) to a 1 liter flask containing deionized water (400 ml) to form a slurry. The pH of the slurry is approximately 8.0 and the temperature approximately 20⁰C.

[00497] Add cobalt chloride (CoCl₂^H₂O) (0.285 g) (Sigma- Aldrich, St. Louis, MO) to a 100 ml beaker containing deionized water (60 ml) to form a clear solution. Add the cobalt solution to the carbon-supported titanum slurry incrementally over the course of 30 minutes (i.e., at a rate of approximately 2 ml/minute) . Maintain the pH of the carbon slurry at from about 7.5 and about 8.0 during addition of the cobalt solution by co- addition of a 0.1 wt% solution of sodium hydroxide (Aldrich Chemical Co., Milwaukee, WI) . Add approximately 1 ml of 0.1 wt .% sodium hydroxide solution to the carbon slurry during addition of the cobalt solution. Monitor the pH of the slurry a pH meter (Thermo Orion, Model 290) .

[00498] After addition of the cobalt solution to the carbon- supported titanum slurry is complete, stir the slurry using a mechanical stirring rod operating at 50% of output (Model IKA- Werke RW16 Basic) for approximately 30 minutes; monitor the pH of the slurry using the pH meter and maintain at about 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide (1 ml) or 0.1 wt .% HNO3 (1 ml) . Heat the slurry under a nitrogen blanket to 45°C at a rate of about 2°C per minute and maintain the pH at 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide (1 ml) or 0.1 wt . % HNO₃ (1 ml) . Upon reaching 45°C, stir the slurry using the mechanical stirring bar described above for 20 minutes at constant temperature of 45°C and a pH of 8.0. Heat the slurry to 50⁰C and adjust its pH to 8.5 by addition of 0.1 wt . % sodium hydroxide solution (5 ml) ; maintain the slurry at these conditions for approximately 20 minutes. Heat the slurry to 6O⁰C, adjust its pH to 9.0 by addition of 0.1 wt . % sodium hydroxide solution (5 ml) and maintain at these conditions for approximately 10 minutes.

[00499] Filter the resulting mixture and wash with a plentiful amount of deionized water (approximately 500 ml) and dry the wet cake for approximately 16 hours in a vacuum oven at 120 ⁰C. The precursor contains approximately 1.0% by weight cobalt and 1% by weight titanium.

[00500] Charge cobalt and titanium-containing precursor (5.0 g) into a Hastelloy C tube reactor packed with high temperature insulation material. Purge the reactor with argon introduced to the reactor at a rate of approximately 100 cm³/min at approximately 20⁰C for approximately 15 minutes. Insert a thermocouple into the center of the reactor for charging the precursor material.

[00501] Raise the temperature of the reactor to approximately 300⁰C over the course of approximately 15 minutes during which time a 10%/90% (v/v) mixture of acetonitrile and argon (Airgas, Inc., Radnor, PA) is introduced to the reactor at a rate of approximately 100 cm³/minute. Increase the temperature of the reactor to approximately 950⁰C over the course of 30 minutes during which time the 10%/90% (v/v) mixture of acetonitrile and argon flow through the reactor at a rate of approximately 100 cm³/minute. Maintain the temperature of the reactor at approximately 950⁰C for approximately 120 minutes.

[00502] Cool the reactor to approximately 20°C over the course of 90 minutes under a flow of argon at approximately 100 cmVminute . The catalyst contains approximately 1% by weight titanium.

Example 21

[00503] This example details the performance of various cobalt-containing catalysts in the oxidation of PMIDA to N- (phosphonomethyl) glycine .

[00504] Two catalyst samples were prepared as described in Example 6 of International Publication No. WO 03/068387 using cobalt tetramethoxyphenyl prophyrin (TMPP) as the source of cobalt. One sample contained 1.5% cobalt on a carbon support designated MC-IO and the other 1.5% cobalt on a carbon support designated CP-117. Hereinafter, the catalysts are designated 1.5%CoTMPP/MC-10 and 1.5%CoTMPP/CP-117, respectively. MC-10 carbon support is described, for example, in Examples 1, 4, and 5 of International Publication No. WO 03/068387 and in U.S. Patent No. 4,696,772 to Chou .

[00505] The performance of these catalysts was compared to the performance of a 1.5%CoCN/C catalyst prepared as described in Example 4 above. MC-IO carbon support was also tested in PMIDA oxidation. All catalyst samples were tested in PMIDA oxidation under the conditions set forth above in Example 10. The maximum CO₂ percentage in the exit gas and the cumulative amount of CO₂ generated were used as indices of catalyst performance. The results are shown in Table 18. Table 18

[00506] As shown in Table 18, the 1.5% CoCN/C prepared as described in Example 4 using CH₃CN exhibited high activity for oxidation of both PMIDA and formaldehyde.

The 1.5%CoTMPP/CP117 and 1.5%CoTMPP/MC10 samples exhibited much lower formaldehyde oxidation activity than this sample. The 1.5%CoTMPP/CP117 sample also exhibited much lower activity for PMIDA oxidation activity as compared to the 1.5%CoCN/C prepared as described in Example 4. Although the 1.5%CoTMPP/MC10 appeared to demonstrate similar PMIDA oxidation activity as compared to the 1.5%CoCN/C sample, it is presently believed that a substantial amount of the PMIDA activity of this catalyst was attributable to the MC-10 support. To test the effectiveness of the MC-10 carbon support for PMIDA oxidation, some modifications were made to the standard testing conditions: either runtime was increased or catalyst loading was increased. At a similar PMIDA conversion level, the MClO catalyst demonstrated similar formaldehyde oxidation activity as the 1.5%CoTMPP/MC10 catalyst.

Example 22

[00507] Various carbon-supported transition metal-containing catalysts and their supports were analyzed to determine their Langmuir surface areas as described in Example 15. The analysis of the catalyst and carbon support surface areas included the total Langmuir surface area, Langmuir surface area attributed to micropores, and Langmuir surface area attributed to mesopores and macropores.

[00508] Catalysts and supports tested included: (1) a carbon support having a Langmuir surface area of approximately 1600 m²/g; (2) a l%FeCN/C catalyst prepared on support (1) as described in Example 1; (3) a 1.5%CoCN/C catalyst prepared on support (1) as described in Example 4; (4) a 1% cobalt phthalocyanine (CoPLCN) catalyst prepared on support (1) prepared as described in Examples 12 and 13; (5) a particulate carbon support sold under the trade name CP-117 (Engelhard Corp., Iselin, NJ) and described in Example 2 of International Publication No. WO 03/068387; (6) a 1.1% FeTPP (iron tetraphenylporphyrin) catalyst prepared on the CP-117 support as described in Example 2 of International Publication No. WO 03/068387; (7) a 1.5% cobalt tetramethoxyphenyl porphyrin (TMPP) catalyst prepared on a CP-117 support as described in Example 6 of International Publication No. WO 03/068387; (8) a particulate carbon catalyst designated MC-IO prepared in accordance with U.S. Patent No. 4,696,772 to Chou and described in Example 1 of International Publication No. WO 03/068387; and (9) a 1.5% cobalt tetramethoxyphenyl porphyrin (TMPP) catalyst prepared on a MC-IO support as described in Example 6 of International Publication No. WO 03/068387. The results are shown in Table 19.

Iron catalysts

[00509] For the Fe-based catalysts with similar metal loading, the l%FeCN/C prepared using CH₃CN exhibited significantly higher total Langmuir surface area as compared to the l%FeTPP/CP117 catalyst (1164 vs. 888 m²/g) . The l%FeCN/C catalyst prepared using CH₃CN possessed 72.9% of the total surface area of the carbon support; the 1. l%FeTPP/CP117 catalysts possessed 55.4% of the total surface area of CP117. These results indicate the l%FeCN/C catalyst exhibited higher metal dispersion than 1. l%FeTPP/CP117 catalyst.

[00510] The pore surface area analysis demonstrated the decrease in surface area between the two catalysts is due primarily to the substantial loss of micropore surface area (i.e., surface area attributed to pores having a diameter of less than 20 A) and some loss in mesopore and macropore surface area (i.e., pores having a diameter between 20 and 80 A).

[00511] The l%FeCN/C catalyst exhibited a micropore surface area of 935 m²/g while the 1. l%FeTPP/CP117 catalyst exhibited a micropore surface area of 696 m²/g. It is presently believed the l%FeCN/C catalyst contained a much higher proportion of micropores, mesopores and macropores than the 1. l%FeTPP/CP117 catalyst .

Cobalt catalysts

[00512] For the Co-based catalysts with similar metal loading, the 1.5%CoCN/C catalyst prepared using CH₃CN exhibited much higher total Langmuir surface area than the 1.5%CoTMPP/CP117 catalyst prepared from the CoTMPP organometallic precursor (1336 vs. 1163 m²/g) . The 1.5%CoCN/C catalyst possessed 83.7% of the total Langmuir surface area of its carbon support; the 1.5%CoTMPP/CP117 catalyst possessed 72.6% of the total surface area of the CP117 support. These results indicated the 1.5%CoCN/C catalyst exhibited higher metal dispersion than the 1.5%CoTMPP/CP117 catalyst. The pore surface area analysis demonstrated the reduced surface area of the 1.5%CoTMPP/CP117 catalyst was primarily due to the loss of micropore surface area and some loss in mesopore and macropore surface area.

[00513] The 1.5%CoCN/C catalyst exhibited a micropore surface area of 1066 m²/g while the 1.5%CoTMPP/CP117 catalyst exhibited a micropore surface area of 915 m²/g. The higher micropore SA observed in 1.5%CoCN/C implies the catalyst has much more micropore than 1.5%CoTMPP/CP117. The results also showed 1.5%CoCN/C had similar amount of meso- and macropore as 1.5%CoTMPP/CP117. It is presently believed the 1.5%CoCN/C catalyst contained a much higher proportion of micropores, mesopores and macropores than the 1.5%CoTMPP/CP117 catalyst.

[00514] Comparison of the 1.5%CoTMPP/MC10 catalyst with the 1.5%CoCN/C catalyst is difficult due to MClO having a much higher surface area than the carbon support used for the 1.5%CoCN/C catalyst. However, useful information can be extracted if we compare the catalysts' surface area as a percentage of the surface area of its carbon support. The 1.5%CoCN/C catalyst possessed 83.7% of the total surface area of its carbon support; the 1.5%CoTMPP/MC10 possessed 75.6% of the total surface area of the MClO carbon support. These results suggested that the 1.5%CoCN/C catalysts have higher metal dispersion than the 1.5%CoTMPP/MC10 catalysts. This conclusion is supported by the microscopy study of these catalysts described in Example 25.

[00515] Based on the foregoing, it is currently believed that metal carbide-nitride or, carbo-nitride, catalysts prepared in accordance with the present invention using CH₃CN exhibit significantly higher surface area and metal dispersion than catalysts prepared from porphyrin or organometallic precursors. Moreover, metal carbide-nitride or, carbo-nitride, catalysts also exhibit a greater proportion of micropores than catalysts prepared from porphyrin or organometallic precursors.

Example 23

[00516] Various catalysts were analyzed by Inductively Coupled Plasma (ICP) analysis to determine their nitrogen and transition metal content. The analysis was carried out using a Thermo Jarrell Ash (TJA) , IRIS Advantage Duo View inductively coupled plasma optical emission spectrometer. The results are shown in Table 20. Catalyst samples analyzed included: (1) a 1.1% FeTPP (iron tetraphenylporphyrin) catalyst on a CP- 117 support prepared generally as described in Example 2 of International Publication No. WO 03/068387; (2) a l%FeCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g; prepared generally as described in Example 1; (3) a 1.5% cobalt tetramethoxyphenyl porphyrin (TMPP) catalyst on a CP-117 support prepared generally as described in Example 6 of International Publication No. WO 03/068387; (4) a 1.5% cobalt tetramethoxyphenyl porphyrin (TMPP) catalyst on a MC-IO support prepared generally as described in Example 6 of International Publication No. WO 03/068387; (5) a 1% cobalt phthalocyanine (CoPLCN) catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Examples 12 and 13; (6) a 1.5% cobalt phthalocyanine (CoPLCN) catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Examples 12 and 13, with precursor deposition modified to provide 1.5% CoPLCN loading; (7) a 5% cobalt phthalocyanine (CoPLCN) catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Examples 12 and 13, with precursor deposition modified to provide 5% CoPLCN loading; (8) a 1%COCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4; (9) a 1.5%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4; (10) a 3%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4, with precursor deposition modified to provide 3% cobalt loading; (11) a 5%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4, with precursor deposition modified to provide 5% cobalt loading; and (12) a 10%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4, with precursor deposition modified to provide 10% cobalt loading.

Table 20

a. Catalysts were synthesized by depositing organometallic compounds on carbon; the precursors were then calcined at 800⁰C under argon for 2 hours as described in Examples 1,2 and 6 of International Publication No. WO 03/068387. b. Catalysts were synthesized by depositing C0CI₂ on carbon; the precursors were then calcined at 950⁰C under an CH₃CN environment for 2 hours. c. Catalysts were synthesized by depositing the organometallic compound on carbon; the precursors were then calcined at 950⁰C under argon for 2 hours.

Example 24

[00517] Various catalysts were characterized by Time-of- Flight Secondary Ion Mass Spectrometry (ToF SIMS) . Catalyst samples analyzed included: (1) a 1.1% FeTPP/CP117 catalyst prepared generally as described in Example 2 of International Publication No. WO 03/068387; (2) a l%FeCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g; prepared generally as described in Example 1; (3) a 1.5%CoTMPP/CP117 catalyst prepared generally as described in Example 6 of International Publication No. WO 03/068387; (4) a 1.5% CoTMPP/MClO catalyst prepared generally as described in Example 6 of International Publication No. WO 03/068387; (5) a 1%COCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4; (6) a 1.5%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4; (7) a 5%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4, with precursor deposition modified to provide 5% cobalt loading; and (8) a 10%CoCN/C catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Example 4, with precursor deposition modified to provide 10% cobalt loading. (9) a 1% cobalt phthalocyanine (CoPLCN) catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Examples 12 and 13.

[00518] The surface of each catalyst sample was secured to double sided tape and analyzed by ToF SIMS (Charles-Evans and Associates) under the following conditions. The ToF SIMS analysis depth was ~10 A. The method described in this example is referenced in this specification and appended claims as "Protocol A. "

Instrument: Physical Electronics TRIFT III Primary Ion Beam: ⁶⁹Ga LMIG (bunched) Primary Beam Potential: 18kV Primary Ion Current (DC) : ~ 2 nA Nominal Analysis Region: 300 x 300 μm Charge Neutralization (~20 eV) : Yes Post Acceleration: 5 kV Masses Blanked: No Energy Filter/Contrast Diaphragm: No/No

[00519] ToF SIMS analysis is also described, for example, in LEFEVRE, M., et al . , "O₂ Reduction in PEM Fuel Cells: Activity and Active Site Structural Information for Catalysts Obtained by the Pyrolysis at High Temperature of Fe Precursors," Journal of Physical Chemistry B, 2000, Pages 11238-11247, Volume 104, American Chemical Society; and LEFEVRE, M., et al . , "Molecular Oxygen Reduction in PEM Fuel Cells: Evidence for the Simultaneous Presence of Two Active Sites in Fe-Based Catalysts," Journal of Physical Chemistry, 2002, Pages 8705- 8713, Volume 106.

[00520] The results for samples (1) and (2) are shown below in Table 21 and the results for samples (3) -(8) are shown below in Table 22.

[00521] Figs. 54 and 55 show the intensities of ion species detected during analysis of the 1. l%FeTPP/CP117 and l%FeCN/C samples, respectively. The relative intensity in Table 21 indicates the proportion of the total intensity associated with each species .

Table 21

[00522] As shown in Table 21, for the 1. l%FeTPP/CP117 prepared using a FeTPP organometallic precursor, the majority of

^Nx^y Υ FeN₂C_y and FeN₄Cv A minor portion of FeN₃Cy⁺ ions was also detected. For the l%FeCN/C catalyst prepared using acetonitrile, the majority of the FeN_xCy ions existed in the form of FeNCyy⁺,' FeN₂C or FeN₃Cy ions. Analysis of the l%FeCN/C catalyst prepared using acetonitrile did not detect FeN₄Cy⁺ ions.

[00523] Table 22 shows the relative intensity of various detectable ions and the relative abundance of different ion families for Co-based catalysts. Table 22

[00524] Fig. 53 shows the ToF SIMS spectrum for the 1.5%CoCN/C sample. Fig. 56 shows the intensities of ion species detected during analysis of the 1.5%CoTMPP/CP117 sample. Fig. 57 shows the intensities of ion species detected during analysis of the 1.0%CoCN/C sample. Fig. 58 shows the intensities of ion species detected during analysis of the 1.5%CoCN/C sample. Fig. 59 shows the intensities of ion species detected during analysis of the 5%CoCN/C sample. Fig. 60 shows the intensities of ion species detected during analysis of the 10%CoCN/C sample. Fig. 61 shows the intensities of ion species detected during analysis of the 1.0%CoPLCN/C sample. Relative intensities for each of the samples (given in Table 22) were determined as described above for the iron samples.

[00525] As shown in Table 22, for the 1.5%CoTMPP/CP117 catalyst prepared using a CoTMPP organometallic precursor, the majority of the CoN_xCy⁺ ions existed in the form of CoN₄Cy⁺ ions along with a minor portion of CoNCy⁺ and CoN₃Cy⁺ ions. CoN₂Cy⁺ ions were not detected in the analysis of the 1.5%CoTMPP/CP117 catalyst .

[00526] For the 1.5%CoTMPP/MC10 catalyst, CoN_xCy⁺ ion signals were not identified, possibly due to the high surface area (2704 m²/g) of the MClO carbon support. Although the 1.5%CoTMPP/CP117 and 1.5%CoTMPP/MC10 catalysts have the same cobalt loading, the 1.5%CoTMPP/MC10 catalyst will exhibit less cobalt species than the 1.5%CoTMPP/CP117 catalyst when comparison is made on a normalized surface area due to the higher surface area MClO carbon support. ToF SIMS is a surface sensitive technique which collects signals from a fixed surface area for different samples. Thus, the results for the 1.5%CoTMPP/MC10 catalyst are likely due to the effect of the support surface area on cobalt density. However, a similar CoN_xC_y ⁺ ion population would be expected in for both 1.5%CoTMPP/MC10 and 1.5%CoTMPP/CP117 as the surface area of the support is not expected to affect ion formation and distribution.

[00527] Regardless of the carbon support used, existence of a major portion of CoN₄C_y ⁺ species in the CoTMPP catalysts is not surprising due to the nature of the metal porphyrin in which the metal centers are coordinated to four nitrogen atoms on the porphyrin rings .

[00528] Similar CoN_xCy⁺ ions and ion distribution were observed for the 1.0%CoCN/C and 1.5%CoCN/C catalysts. For each, the majority of the CoN_xCy⁺ ions existed as CoNCy⁺ and CoN₂Cy⁺ ions along with CoN₃Cy⁺ ions. CoN₄Cy⁺ ions were not detected in analysis of either sample.

[00529] As cobalt loading increased, the proportion of CoNCy⁺ ions decreased and CoN₄Cy⁺ ions were observed in analysis of the 5%CoCN/C and 10%CoCN/C samples. Significant amounts of CoN₂Cy⁺ and CoN₃Cy⁺ ions were detected for each of these samples.

[00530] As shown in Example 21, the CoCN/C catalysts exhibited superior reaction performance (i.e., higher PMIDA and formaldehyde oxidation activity) as compared to the CoTMPP/C catalysts .

[00531] As shown in Example 14, reaction performance of CoCN/C catalysts decreased slightly as cobalt loading increased (i.e., those CoCN/C samples in which CoN₄Cy⁺ ions were observed exhibited decreased performance as compared to those CoCN/C samples in which CoN₄Cy⁺ ions were not observed) . Based on these results, it is believed that the CoNC_y ⁺ are the major catalytic sites for PMIDA and formaldehyde oxidation with CoNC_y ⁺ also contributing catalytic activity.

Example 25

[00532] This example details transmission electron microscopy (TEM) analysis of various catalyst samples following the procedure described in Example 18. Samples analyzed included: (1) a 1% cobalt phthalocyanine (CoPLCN) catalyst on a carbon support having a Langmuir surface area of approximately 1600 m²/g prepared generally as described in Examples 12 and 13; (2) a 1.5%CoTMPP/MC10 catalyst prepared generally as described in Example 6 of International Publication No. WO 03/068387; (3) a 1.5% COTMPP/CP117 catalyst prepared generally as described in Example 6 of International Publication No. WO 03/068387.

[00533] Figs. 62A, 62B, 63A and 63B are TEM images for the 1% CoPLCN/C sample. High magnification TEM analysis reveals that most of the Co-related particles are associated with some graphitic features (see Fig. 62A), suggesting that during the catalyst preparation process, Co stimulates the graphitization of the carbon substrates (see Figs. 63A and 63B). From some low-density carbon substrates, larger cobalt-based particles of 10-16 nm in diameter have been observed.

[00534] Figs. 64A and 64B are TEM images for the

1.5%CoTMPP/MC10 sample. Many larger particles of from 18-20 nm in diameter were detected in the TEM analysis for the 1.5%CoTMPP/MC10 sample. In contrast, as shown in Figs. 27-33 (Example 31), Co-based particles of a size above the detection limit (1 nm in diameter) of this SEM analysis were not detected for the 1.5%CoCN/C catalyst. Based on the foregoing, it is currently believed that the cobalt species in this sample likely exist in an amorphous form or in particles of a size below 1 nm.

[00535] Figs. 65A and 65B are TEM images for the 1.5%CoTMPP/CP117 sample. No Co-based particles within our TEM detecting limit of 1 nm in diameter were detected (see Figs. 65A and 65B) .

Example 26

[00536] A 1.5% cobalt catalyst prepared as described in Examples 3 and 4 and a catalyst prepared as described in Wan et al. International Publication No. WO 2006/031938 containing 5% platinum and 0.5% iron deposited on a carbon support (5%Pt/0.5%Fe catalyst) were tested in the oxidation of N- (phosphonomethyl) iminodiacetic acid (PMIDA).

[00537] The PMIDA oxidation was conducted in a 200 ml glass reactor containing a total reaction mass (200 g) which included water (188.3 g) , 5.74% by weight PMIDA (11.48 g) and 0.11% catalyst (0.21 g) . The oxidation was conducted at a temperature of 100⁰C, a pressure of 60 psig, (a stir rate of 1000 revolutions per minute (rpm) ) , under an oxygen flow of 100 cm³/minute and under a nitrogen flow of 100 cm³/min.

[00538] As shown in Table 23, 6 reaction cycles to varying degrees of conversion (i.e., varying residual PMIDA concentration in the reactor) were carried out with each of the catalysts. Oxidation of PMIDA was monitored by electrochemical detection (ECD) using a dual probe ECD electrode mounted in the bottom of the reactor. The voltage required to maintain a select current density between the electrodes was monitored throughout the cycle to the varied residual PMIDA contents in the reaction mixture. The change in ECD values (i.e., ΔECD) was determined from the maximum and minimum ECD voltages observed during each cycle. The results are provided in Table 23.

[00539] The performance of each of the catalyst samples in PMIDA oxidation (under the conditions set forth above) was analyzed by allowing the reaction to proceed to pre-determined ΔECD values; the ΔECD value endpoints selected were those corresponding to a residual PMIDA content in the reactor of approximately 0.1% by weight as shown in Table 23 above. The ΔECD value for the 1.5% cobalt catalyst was approximately 1.00V and the ΔECD value for the 5%Pt/0.5%Fe catalyst was approximately 1.18V. 5 reaction cycles were carried out using the 1.5% Co catalyst while 6 cycles were carried out using the 5%Pt/0.5%Fe catalyst.

[00540] Fig. 66 shows a plot of time to reach the target ΔECD value versus reaction cycle (i.e., reaction runtime plot) as an indicator of catalyst stability with stability increasing as the slope of the plot decreases. The slope of the plot for the 1.5% Co catalyst was 1.42 while the slope of the plot for the 5%Pt/0.5%Fe catalyst was 1.46. Table 24 provides a comparison of the selectivity of the catalysts to conversion of PMIDA, N- formylglyphosate (NFG) , formaldehyde (FM) , formic acid (FA) , iminodiacetic acid (IDA) , aminomethylphosphonic acid (AMPA) , N- methy-N- (phosphonomethyl) glycine (NMG) , imino-bis- (methylene) -bis- phosphonic acid (iminobis) , phosphate ion (PO₄) , glycine and methyl aminomethylphosphonic acid (MAMPA) based on the endpoint concentration of each of these components in the reaction mixture (determined by High Performance Liquid Chromatography) observed when using each of the catalysts.

[00541] The performance of each of the catalyst samples in PMIDA oxidation (under the conditions set forth above) was also analyzed by allowing the reaction to proceed for an additional 12 minutes after reaching the pre-determined ΔECD value endpoints described above. 7 reaction cycles were carried out using each of the catalysts. Fig. 67 shows the reaction endpoint runtime plots; the slope of the plot for the 1.5% cobalt catalyst was 1.85 while the slope of the plot for the 5%Pt/0.5%Fe catalyst was 1.61. Table 25 provides a comparison of the selectivity towards oxidation of the various compounds set forth above based on the endpoint concentration of the compounds at the reaction endpoint (as determined by HPLC) observed when using each of the catalysts.

Example 27

[00542] A particulate carbon support designated D1097 (10.00 g) having a Langmuir surface area of approximately 1500 m²/g was added to a 1 liter flask containing deionized water (400 ml) to form a slurry.

[00543] Cobalt nitrate hexahydrate (Co (NO₃) ₂ • 6H₂O) (0.773 g) (available from Aldrich Chemical Co., Milwaukee, WI) was introduced to 60 ml of a 50/50 (v/v) mixture of diglyme (diethylene glycol dimethyl ether) (also available from Aldrich Chemical Co., Milwaukee, WI) and deionized water in a 100 ml beaker.

[00544] The cobalt-diglyme mixture was added to the carbon slurry incrementally over the course of approximately 30 minutes (i.e., at a rate of approximately 2 ml/minute) to produce a cobalt-diglyme-carbon mixture. The pH of the carbon slurry was maintained at from about 7.5 to about 8.0 during addition of the cobalt solution by co-addition of a 0.1 wt% solution of sodium hydroxide (Aldrich Chemical Co., Milwaukee, WI) . Approximately 1 ml of 0.1 wt .% sodium hydroxide solution was added to the carbon slurry during addition of the cobalt solution. The pH of the slurry was monitored using a pH meter (Thermo Orion, Model 290) .

[00545] The cobalt-diglyme-carbon mixture was stirred using a mechanical stirring rod operating at 50% of output (Model IKA- Werke RW16 Basic) for approximately 30 minutes; the pH of the mixture was monitored using the pH meter and maintained at approximately 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide or 0.1 wt . % HNO₃. The mixture was then heated under a nitrogen blanket to approximately 45°C at a rate of approximately 2°C per minute while maintaining the pH at approximately 8.0 by dropwise addition of 0.1 wt . % sodium hydroxide or 0.1 wt . % HNO3. Upon reaching approximately 45°C, the mixture was stirred using the mechanical stirring bar described above for 20 minutes at a constant temperature of approximately 45°C and a pH of approximately 8.0. The mixture was then heated to approximately 50⁰C and its pH was adjusted to approximately 8.5 by addition of 0.1 wt .% sodium hydroxide solution; the mixture was maintained at these conditions for approximately 20 minutes. The slurry was then heated to approximately 60⁰C, its pH adjusted to 9.0 by addition of 0.1 wt . % sodium hydroxide solution (5 ml) and maintained at these conditions for approximately 10 minutes.

[00546] The resulting mixture was filtered and washed with a plentiful amount of deionized water (approximately 500 ml) and the wet cake was dried for approximately 16 hours in a vacuum oven at approximately 120⁰C to provide a catalyst precursor.

[00547] Cobalt-containing catalyst precursor (5 g) was charged into the center of a Hastelloy C tube reactor packed with high temperature insulation material; thermocouple was inserted to monitor the temperature. The reactor was purged with argon that was introduced to the reactor at a rate of approximately 100 cm³/min at approximately 20⁰C for approximately 15 minutes.

[00548] The temperature of the reactor was then raised to approximately 30⁰C during which time acetonitrile (available from Aldrich Chemical Co. (Milwaukee, WI) was introduced to the reactor at a rate of approximately 10 cm³/minute. The reactor was maintained at approximately 950⁰C for approximately 120 minutes .

[00549] The reactor was cooled to approximately 20⁰C over the course of 90 minutes under a flow of argon at approximately 100 cmVminute.

[00550] The resulting catalyst contained approximately 1.5% by weight cobalt.

[00551] A second catalyst containing approximately 3% by weight cobalt was prepared in this manner by doubling the amount of cobalt source (i.e., 1.545 g of cobalt nitrate hexahydrate) . [00552] The 1.5% and 3% cobalt catalysts prepared using diglyme were tested in PMIDA oxidation under the conditions set forth in Example 26 that was monitored by electrochemical detection (ECD) and their performance was compared to that of the 5%Pt/0.5%Fe catalyst prepared as described in Wan et al . International Publication No. WO 2006/031938. The target ΔECD value for the 1.5% cobalt and 3% cobalt catalysts was approximately 1.00 V. As in Example 26, the ΔECD value for the 5%Pt/0.5%Fe catalyst was approximately 1.18V.

[00553] The cobalt-containing catalysts were tested in each of 6 PMIDA reaction cycles while the 5%Pt/0.5%Fe catalyst was tested in each of 8 reaction cycles. Fig. 68 shows the reaction endpoint runtime plots for each catalyst. The slope of the plot for the 1.5% cobalt catalyst was 1.81, the slope of the plot for the 5%Pt/0.5%Fe catalyst was 1.61 while the slope of the plot for the 3% cobalt catalyst was 1.09.

[00554] Another catalyst (1) containing 3% cobalt was prepared as described above using diglyme. Two catalysts containing 3% cobalt were also prepared as described above using tetraglyme (2) and polyglyme (3) rather than diglyme. Each of the catalysts was tested in PMIDA oxidation under the conditions set forth in Example 49 in each of 5 reaction cycles. For each reaction cycle, the reaction was carried out for an additional 12 minutes after reaching the predetermined ΔECD value of 1.00 V for each of the catalysts. Fig. 69 shows a plot of time to reach the predetermined endpoint versus reaction cycle for each of the catalysts. As shown in Fig. 69, the time axis-intercept for the plot for the catalyst prepared using diglyme was approximately 32.7 and its slope was approximately 1.23; the time axis-intercept for the plot for the catalyst prepared using tetraglyme was approximately 27.7 and its slope was approximately 1.95; the time axis-intercept for the plot for the catalyst prepared using polyglyme was approximately 35.3 and its slope was approximately 0.80.

Example 28

[00555] This Example details preparation of various iron and cobalt-containing catalysts prepared generally as described in Example 27.

[00556] Catalysts containing 3% iron were prepared generally in accordance with the method described in Example 27. A particulate carbon support (1Og) having a Langmuir surface area of approximately 1500 m²/g described in Example 27 was was added to a 1 liter flask containing deionized water (400 ml) to form a slurry. Iron chloride (FeCl₃«H₂O) (1.497 g) (available from Aldrich Chemical Co., Milwaukee, WI) was introduced to 60 ml of a 50/50 (v/v) mixture of diglyme (diethylene glycol dimethyl ether) (also available from Aldrich Chemical Co., Milwaukee, WI) and deionized water in a 100 ml beaker. The iron-diglyme mixture was added to the carbon slurry incrementally over the course of approximately 30 minutes (i.e., at a rate of approximately 2 ml/minute) to produce an iron-diglyme-carbon mixture. The pH of the carbon slurry was maintained at from about 4.0 and about 4.4 during addition of the iron-diglyme mixture to the carbon slurry by co-addition of sodium hydroxide solution (Aldrich Chemical Co., Milwaukee, WI) . The iron- diglyme-carbon mixture was stirred using a mechanical stirring rod operating at 50% of output (Model IKA-Werke RW16 Basic) for approximately 30 minutes; the pH of the mixture was monitored using the pH meter and maintained at approximately 4.4 by dropwise addition of 0.1 wt . % sodium hydroxide. The mixture was then heated under a nitrogen blanket to approximately 70⁰C at a rate of approximately 2°C per minute while maintaining the pH at approximately 4.4 by dropwise addition of 0.1 wt . % sodium hydroxid. Upon reaching approximately 70⁰C, the pH of the mixture was raised by addition of a 0.1 wt . % sodium hydroxide solution according to the following pH profile: 10 minutes at pH of approximately 5.0, 20 minutes at pH of approximately 5.5, followed by continued stirring at pH of 6.0 until the pH became relatively constant. The resulting mixture was filtered and washed with a plentiful amount of deionized water and the wet cake was dried for approximately 16 hours in a vacuum oven at 120⁰C to provide a catalyst precursor. Iron-containing catalyst precursor (5 g) was charged into the Hastelloy C tube reactor and heat treated as described above regarding preparation of the cobalt-containing catalysts . A catalyst containing 3% iron was also prepared using this method using polyglyme in place of diglyme. (Entries 1 and 2 in Table 26)

[00557] Catalysts containing 3% cobalt were also prepared in accordance with the method detailed in Example 27 using various liquid media. For each 3% cobalt catalyst, cobalt nitrate hexahydrate (1.545 g) was introduced to 60 ml of a 50/50 (v/v) of water and an additional component.

[00558] The liquid media used included 50/50 (v/v) mixtures of water and diethylene glycol diethyl ether, diethylene glycol ethyl ether acetate, Dipropylene glycol methyl ether, 12-crown-4 (1, 4, 7, 10-tetraoxacyclododecane) (a crown analog to polygylme) , 18-crown-6 (1, 4, 7, 10, 13, 16- hexaoxacylclooctadecane, and tetraethylene glycol. (Entries 6, 7, and 9-12 in Table 26) (Entries 3 and 16 in Table 26 correspond to 3% Co catalysts prepared as described in Example 27 using diglyme while entries 4 and 5 correspond to 3% Co catalysts prepared using tetraglyme and polyglyme, respectively)

[00559] A catalyst containing 0.5% Co was prepared by introducing cobalt nitrate hexahydrate (0.258 g) to 60 ml of a 50/50 (v/v) mixture of water and N, N, N', N', N" Pentamethyldiethylenetriamine . (Entry 8 in Table 26) [00560] In addition, a 3% Co catalyst was prepared by introducing cobalt nitrate hexahydrate (1.545 g) to a mixture containing 30 ml of a 50/50 (v/v) mixture of water and ethanol and 30 ml of diglyme. (Entry 13 in Table 26)

[00561] A 3% Co catalyst was also prepared by introducing cobalt nitrate hexahydrate (1.545 g) to 60 ml of a 50/50 (v/v) mixture of ethanol and diglyme. (Entry 14 in Table 26) A 3% Co catalyst was also prepared by introducing cobalt nitrate hexahydrate (1.545 g) to 60 ml of ethanol. (Entry 15 in Table 26)

[00562] A 4% Co catalyst was prepared generally as described in Example 50 by introducing cobalt nitrate hexahydrate (2.06 g) to 60 ml of a 50/50 (v/v) mixture of polyglyme and deionized water. (Entry 17 in Table 26)

[00563] A catalyst containing 3% Co and 1% nickel was prepared by introducing cobalt nitrate hexahydrate (1.545 g) and nickel dichloride hexahydrate (NiCl₂'6H₂O) (0.422 g) to a 50/50 (v/v) mixture of diglyme and deionized water. (Entry 18 in Table 26)

[00564] A 3% Co catalyst was also prepared by introducing cobalt nitrate hexahydrate (1.545 g) to 60 ml of n-butanol. (Entry 19 in Table 26)

[00565] Each of the catalysts was tested in PMIDA oxidation was conducted in a 200 ml glass reactor containing a total reaction mass (200 g) which included water (188.3 g) , 5.74% by weight PMIDA (11.48 g) and 0.15% catalyst (0.30 g) . The oxidation was conducted at a temperature of 100⁰C, a pressure of 60 psig, (a stir rate of 1000 revolutions per minute (rpm) ) , under an oxygen flow of 175 cm³/minute and under a nitrogen flow of 175 cm³/min. The performance of each of the catalyst samples in PMIDA oxidation was analyzed over the course of 6 reaction cycles by allowing the reaction to proceed to 12 minutes past the pre-determined ΔECD values determined as set forth above in Example 26. The predetermined ΔECD value for each of the catalyst samples was 1.00 V. The intercepts and slopes of the plots of time to reach the predetermined ΔECD value versus reaction cycle are provided in Table 31.

Table 26

Ethanol (EtOH)

1 Diglyme

2 Polyglyme (with an averaged Mn of 1000)

3 Tetraglyme

4 Diethylene glycol diethyl ether

5 Diethylene glycol ethyl ether acetate

6 N, N, N ',N ',N" Pentamethyldiethylenetriamine

7 Dipropylene glycol methyl ether

8 12-crown-4 (1, 4, 7, 10-tetraoxacyclododecane) (a crown analog to polygylme)

9 18-crown-6 (1, 4, 7, 10, 13, 16-hexaoxacylclooctadecane

10 Tetraethylene glycol

[00566] l%FeCN/C, 1.5.%CoCN/C, 1. l%FeTPP/CP117, and 1.5%CoTMPP/CP117 catalysts were also tested in PMIDA oxidation; these catalysts exhibited lower activity and stability than those catalysts set forth in Table 26.

Example 29

[00567] The catalysts prepared as described in Examples 27 and 28 were analyzed to determine their Langmuir surface areas (e.g., total Langmuir surface area, Langmuir surface area attributed to micropores, and Langmuir surface area attributed to mesopores and macropores) as described in Example 15. The results are shown in Table 27.

[00568] For comparison purposes, a catalyst prepared as described in Example 27 by introducing cobalt nitrate (1.545 g) to 60 ml of diglyme was prepared and analyzed; neat carbon support used in Examples 27 and 28 was heat treated as described in Example 27 was also analyzed. Table 27 (Entry Nos. are with reference to Table 26)

[00569] Fig. 70 shows the pore volume distribution for samples the carbon support, the acetonitrile-treated support, the 3% Co catalyst prepared using 100% diglyme, and Entry Nos. 3-5.

[00570] Table 28 shows the pore volume distribution (pore surface areas, PSA) for Entry Nos. 6, 8, 9, 10, 14, and 15 in Table 26. Table 28

[00571] Table 29 provides a comparison of the samples analyzed to determine their surface areas in this Example and Examples 15 and 22. Table 29

Example 30

[00572] Catalysts prepared as described in Examples 28 and 29 were analyzed by Inductively Coupled Plasma (ICP) analysis as described in Example 16 to determine their transition metal and nitrogen content. The results are shown in Table 30.

Example 31

[00573] This example details scanning electron microscopy (SEM) and transmission electron microscopy (TEM) of various catalysts prepared as described in Examples 27 and 28. Table 31 lists the catalysts analyzed and the corresponding Figs, providing the results. A 3% Co catalyt prepared generally as described in Example 27 in which the cobalt source was introduced to a liquid medium consisting of water was also prepared and analyzed.

Example 32

[00574] Various catalysts prepared as described in Examples 27, 28, and 31 were analyzed by small angle X-ray scattering (SAXS) analysis. FeTPP/CP117, CoTMPP/CP117, and CoTMPP/MCIO catalysts prepared in accordance with Examples 2 and 6 of International Publication No. WO 03/068387 were also analyzed by SAXS. SAXS is a technique for studying structural features of nanoparticles . It is performed by focusing a low divergence x- ray beam onto a sample and observing a coherent scattering pattern that arises from electron density inhomogeneities within the sample. Since the dimensions typically analyzed are much larger than the wavelength of the typical x-ray used (e.g., 1.54°, for Cu), dimensions from tens to thousands of angstroms can be analyzed within a narrow angular scattering range. This angular range or pattern is analyzed using the inverse relationship between particle size and scattering angle to distinguish characteristic shape and size features within a given sample. The instrument used for the SAXS analysis was the Rigaku Ultima III X-ray diffraction and/or scattering system configured with a line source for standard and high-resolution materials analysis. The system has variable slits, which are ideal for low angle diffraction or scattering. The stages include a six position sample changer, thin-film stage and a small-angle transmission stage. A two-bounce germanium monochromator makes the system suitable for high resolution rocking curves and reflectivity, and a multilayer mirror for grazing incident studies or reflectomatry can also condition the incident beam. For the SAXS analysis, the X-ray is generated from a copper target operated at 4OkV and 10OmA, and the irradiated area is approximately 100 mm². The scanning speed of the X-ray beam is 0.1 degree per minute. The dry catalyst powder can be directly analyzed and no special sample preparation is required.

[00575] Table 32 shows the samples analyzed and the corresponding Figure (s) showing the observed particle size distribution .

[00576] Table 32A provides particle size distributions for various catalysts analyzed by SAXS.

Example 33

[00577] This example details X-ray Photoelectron Spectroscopy (XPS) analysis of various catalysts prepared as described in Example 29 under the conditions set forth in Table 33. The samples analyzed and the Figs, providing the corresponding spectra are set forth in Table 34. An iron- contiaining catalyst prepared as described in Example 1 above and a FeTPP/CP117 catalyst prepared in accordance with Example 2 of International Publication No. WO 03/068387 were also analyzed .

Table 33

Example 34

[00578] Various catalysts prepared in accordance with one of the preceding examples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Example 24. The samples analyzed and the corresponding tables providing ion family information and corresponding figures showing intensity of ion species are shown in Table 35. Fig. 108 shows the average relative intensity for various ion species for various samples analyzed.

Table 35

Example 35

[00579] This example details Electron Paramagnetic Resonance (EPR) Spectroscopy analysis of various catalysts prepared as described in Examples 27 and 28. Entry Nos. 3-6, 8-10, 14, and 15 of Table 26 above were analyzed. For comparison purposes, the following samples were analyzed as well:

(1) a carbon support having a Langmuir surface area of approximately 1500 m²/g impregnated with Co phthalocyanine that was calcined in Argon for 2 hours;

(2) a 1.5%CoTMPP/MC10 catalyst prepared in accordance with Example 6 of WO 03/068387; and

(3) catalysts containing 1.5% and 3% cobalt prepared in accordance with Example 27 in which the cobalt source was mixed with the carbon support in a liquid medium consisting of deionized water prior to heat treatment.

[00580] Each catalyst was dried to obtain a constant amount of catalyst per centimeter in the EPR tube. A catalyst sample (0.05 g) was diluted 10:1 on a weight basis with silica gel (Grade 15, Aldrich stock no. 21,448-8, 30-60 mesh) in a vial that was vigorously shaken. The diluted catalyst sample was then ground for further mixing of the catalyst and diluent.

[00581] Q-band EPR spectra for each sample were collected at room temperature (approximately 20-25⁰C) using a Varian E-15 spectrometer Q-band having a TEOIl cavity. The magnetic fields were calibrated using a Varian NMR Gaussmeter and the microwave frequency was measured with an EIP Model 578 frequency counter equipped with a high-frequency option.

[00582] The EPR signal for each catalyst is a first derivative curve that is integrated once to provide an absorption signal and integrated once more to provide the area under the absorption curve that corresponds to the EPR signal intensity. Thus, EPR signal intensity is reported as a "double integral." Accordingly, the EPR signal intensity varies as the inverse square of the linewidth if the shape of the line does not change.

[00583] The samples were analyzed using a spectral window of either from 7000 to 17,000 Gauss or from 6806 to 15,376 Gauss. The absorbance for the samples extended beyond the spectral window. The absorbances were modeled using a mixed Gaussian- Lorentzian lineshape. The thus modeled lineshapes were highly anisotropic, particularly with respect to their linewidth. Figs. 109A and 109B show the spectra thus obtained.

[00584] The number of spins/gram for each sample was determined. As a standard, copper sulfate pentahydrate (CuSO₄ -5H₂O, MW: 249.69 g/mol) was analyzed. The molecular weight of the CuSO₄-SH₂O sample corresponds to approximately 2.41 * 10²¹ spins per gram based on the number of Cu²⁺ ions per gram of the compound. The spins/gram of this strong pitch standard was measured by the above method to be 2.30 * 10²¹ spins per gram was measured. A Cθ3θ₄ standard was also analyzed and, as shown in Table 38, exhibited approximately 1.64E23 spins per mole cobalt that also generally agrees with the spins/mole cobalt expected based on stoichiometry . That is, the standard has one mole of Co²⁺ and two moles Co³⁺ ions per mole of material, but only the Co²⁺ ions give an EPR signal; thus, in theory, one expects 2.01E23 (0.333 * 6.022E23) spins/mole cobalt.

[00585] As shown in Table 38, spins/gram catalyst and spins/mole cobalt readings were not detected for the Co phthalocyanine-impregnated support and the 1.5%CoTMPP/MC10 catalyst. The observed spins/gram catalyst and spins/mole cobalt for the remaining samples were found to be higher than would be expected based on the stoichiometry. [00586] The method described in this example is referenced s specification and appended claims as "Protocol B."

Table 38

1. Double integral over the spectral window divided by the gain

2. Distance (in Gauss) between the positive and negative peaks in the derivative spectrum

A = Signal too weak to quantify B = 7000-17, 000 Gauss C = 6806-15, 376 Gauss

Example 36

[00587] A 3%CoCN/C catalyst prepared as described in Example 50 and 1.5%CoTMPP/MC10 and 1.5%CoTMPP/CP117 catalysts prepared in accordance with Example 6 of WO 03/068387 were tested in PMIDA oxidation under the conditions set forth in Example 28.

[00588] The reaction was run for the times set forth in Table 39 for each of 6 cycles for the 3%CoCN/C catalyst and for the times set forth in Table 39 for each of 3 reaction cycles for the 1.5%CoTMPP/MC10 catalyst. The metal content of the reaction mixture was determined upon completion of each reaction cycle. For the 1.5%CoTMPP/CP117 catalyst, the reaction was discontinued after a reaction time of approximately 100 minutes due to plugging of the gas frit used to sparge the oxygen and nitrogen into the reaction. The metal content of the reaction mixture was determined after the reaction was discontinued. The metal content of the reaction mixtures was determined by ICP-MS using using a VG PQ ExCeIl Inductively Coupled Plasma-Mass Spectrometer .

[00589] As shown in Table 39, the 3%CoCN/C catalyst exhibited low metal leaching over the course of the 6 reaction cycles while the 1.5%CoTMPP/MC10 catalyst exhibited significantly higher metal leaching during its first reaction as compared to the 3%CoCN/C catalyst. The 1.5%CoTMPP/CP117 exhibited relatively low metal leaching; however, this is currently believed to be due the fact that the reaction medium had not yet reached a relatively high oxidation potential associated with a relatively high conversion of PMIDA that tends to promote metal leaching. In contrast, the degree of conversion achieved with the 3%CoCN/C catalyst would subject the catalyst to a relatively high reaction potential. However, this catalyst exhibited resistance to metal leaching under these conditions .

Example 37

[00590] This example details hydrogen generation during PMIDA oxidation conducted under the conditions set forth in Example 26 using different catalysts. The catalysts tested included a 3% cobalt catalyst prepared as described in Example 27, a 5%Pt/0.5%Fe catalyst prepared as described in Wan et al . International Publication No. WO 2006/031938, and a particulate carbon catalyst described in U.S. Patent No. 4,696,772 to Chou .

[00591] Fig. 110 shows the hydrogen generation profiles for the 3% cobalt catalyst over the course of the 6 reaction cycles.

[00592] Fig. Ill shows the first cycle hydrogen generation profile for each of the three catalysts for a reaction time of approximately 50 minutes. At this reaction time, very low residual levels of PMIDA were observed with the 3% cobalt catalyst and the 5%Pt/0.5%Fe catalyst. [00593] Fig. 112 shows the first cycle hydrogen generation profile for the 3% cobalt catalyst and the 4,696,772 catalyst at similar PMIDA conversion levels (i.e., at a reaction time of approximately 50 minutes for the 3% cobalt catalyst and a reaction time of approximately 95 minutes for the 4,696,772 catalyst) The maximum hydrogen generation for the 3% cobalt catalyst was approximately three times that of the 4,696,772 catalyst while the total amount of hydrogen generated with the 3% cobalt catalyst was approximately 37% higher than observed with the 4,696,772 catalyst.

Example 38

[00594] This example details detection of hydrogen peroxide in the PMIDA reaction product of PMIDA oxidation catalyzed using a 3%CoCN/C catalyst prepared using diglyme as described in Example 27. The protocol relies on oxidation of VO⁺² by hydrogen peroxide to produce a diperoxo anion (e.g., VO(O-O₂)]^' in a neutral medium yielding a yellowish medium and oxidation to produce a diperoxo cation (e.g., VO(O-O)J⁺ in an acidic medium to produce a reddish medium.

[00595] 20 ml of the reaction product (taken at a reaction time of approximately 50 minutes) was mixed with 10 ml of an aqueous solution containing 1% VOSO₄ and the color of the resulting solution was recorded. The color of the solution was yellowish green, indicating hydrogen peroxide was present in the reaction product. As an estimate of the hydrogen peroxide content, a solution of similar color was prepared by mixing approximately 625 ppm of hydrogen peroxide with the VOSO₄ solution .

[00596] IR spectra of the reaction product were determined. Two wavelengths of hydrogen peroxide (e.g., 2828 and 1362 cm^'1) were used to determine the presence of hydrogen peroxide. No clear hydrogen peroxide peaks were identified, possibly due to the presence of glyphosate and other reaction products in the samples. Since the detection limit of hydrogen peroxide was estimated to be approximately 3000 ppm and based on the 625 ppm used to prepare the yellowish green solution, the hydrogen peroxide concentration in the 50 minute reaction runtime product was estimated to be from approximately 625 to approximately 3000 ppm.

Example 39

[00597] A catalyst containing approximately 1.5% by weight cobalt prepared as described above in Example 4 was tested for oxidation of PMIDA under the conditions set forth above in Example 2. A 1.5% cobalt catalyst of this type which was heated in an argon atmosphere at approximately 1050⁰C for approximately 3 hours was also tested in PMIDA oxidation.

[00598] The maximum carbon dioxide generation and reaction time, respectively, are set forth in Table 40. Based on these results, the performance of the annealed catalyst represented a drop in activity as compared to the fresh catalyst of approximately 60%.

Table 40

[00599] The fresh and annealed catalyst was also characterized by electron microscopy generally in accordance with the method set forth in Example 25. Photomicrographs for the fresh and annealed catalysts are shown in Figs. 113A and 113B, respectively. As noted in Example 25 in connection with similar samples, microscopy analysis of the fresh catalyst did not detect metal-containing particles. In contrast, microscopy of the annealed catalyst detected metal-containing particles having a largest dimension in the range of from approximately 20 nm to 60 nm.

[00600] Based on the activity and microscopy results for the fresh and annealed catalysts, it is currently believed that the active, fresh catalyst includes a cobalt-containing active phase at least a portion of which is in an amorphous form and/or includes metal-containing particles of a size below the microscopy detection limit.

Example 40

[00601] A catalyst containing approximately 3% by weight cobalt prepared as described above in Example 27 was tested for oxidation of PMIDA for 42 reaction cycles. The PMIDA oxidation was conducted in a reactor containing a total reaction mass (180 g) which included water (157.3 g) , 12.1% PMIDA (21.8 g) , and 0.5% catalyst (0.9 g) . The oxidation was conducted at a temperature of approximately 100⁰C, a pressure of approximately 110 psig, and under an oxygen flow of approximately 600 cm³/min. Used catalyst was also tested under these conditions. The activity of the used catalyst was approximately 1/3 of the fresh catalyst activity.

[00602] Fresh and used catalyst was characterized by electron microscopy generally in accordance with the method set forth in Example 25. Photomicrographs for the fresh and annealed catalysts are shown in Figs. 114A and 114B, respectively .

[00603] The microscopy data were used to calculate an average particle size for the fresh catalyst of approximately 14 nm and an average particle density of approximately 78 particles/μm² and an average particle size for the used catalyst of approximately 20 nm and an average particle density of approximately 162 particles/μm². The increase in average particle size is currently believed to suggest sintering of undetected fresh catalyst particles during oxidation testing. In combination with the lower activity of the used catalyst, it is currently believed that these results suggest that at least a portion of the activity of the fresh catalyst is provided by a cobalt-containing active phase in an amorphous form and/or including metal-containing particles of a size below the microscopy detection limit.

Example 41

[00604] Table 41 summarizes the results of testing of various catalysts under the conditions set forth in Example 10. The catalyst material tested included:

(1) a 5wt% platinum/0.5 wt% iron catalyst prepared generally in accordance with U.S. Patent No. 6,417,133 to Ebner et al . and Wan et al. International Publication No. WO 2006/031938;

(2) a 50:50 (wt/wt) mixture of Catalyst 1 and a 1.5% Co catalyst prepared as described in Example 1 (e.g., the mixture described in Example 11) ;

(3) a 1% Co catalyst prepared generally utilizing the method described in Example 4 that also included approximately 2.5 wt% platinum deposited in accordance with methods known in the art;

(4) a 1% Co catalyst prepared generally utilizing the method described in Example 4 that also included approximately 2.5 wt% platinum deposited and 0.3 wt% iron deposited in accordance with methods known in the art; and

(5) a 1% Co catalyst prepared generally utilizing the method described in Example 4.

[00605] Results for testing of (1) and (2) also appear in Table 6 in Example 11.

Example 42

[00606] This Example provides the results of testing of various catalysts for oxidation of PMIDA under the following conditions. The PMIDA oxidation was conducted in reactor containing a total reaction mass (180 g) which included water (168.2 g) , 5.74 wt% PMIDA (11.48 g) , and 0.16 wt% (0.3 g) catalyst or a mixture of catalysts. The PMIDA oxidation was conducted at a temperature of approximately 100⁰C, a pressure of approximately 60 psig, and an oxygen flow rate of approximately 150 cm³/min. The reaction was stopped at a predetermined endpoint of residual PMIDA concentration of less than approximately 500 ppm, or proceeded for 12 minutes past reaching this predetermined endpoint.

[00607] The catalysts tested included:

(1) a 5%Pt/0.5% Fe on carbon support catalyst prepared generally in accordance with Wan et al. International Publication No. WO 2006/031938; (2) a 50/50 (wt/wt) mixture of catalyst (1) and a 3% Co catalyst prepared as described in Example 27;

(3) catalyst (2) for 12 minutes past the predetermined endpoint;

(4) a 3% Co catalyst prepared as described in Example 27; and

(5) catalyst (4) for an additional 12 minutes past the predetermined endpoint.

[00608] These results indicate that terminating the reaction at the predetermined endpoint provided greater stability with respect to formic acid oxidation as compared to continuing operation beyond the predetermined endpoint.

Example 43

[00609] This example details the testing of various materials and combinations thereof in PMIDA oxidation. The materials were tested in PMIDA oxidation in a reactor containing a total reaction mass (180 g) which included water (154.8 g) , 12% PMIDA (21.6 g) , 2% (3.6 g) catalyst material. The reaction was conducted at a temperature of approximately 100⁰C, a pressure of 60 psig, under an oxygen flow of approximately 100 cm³/min to a predetermined endpoint as described in Example 26. The source of bismuth was introduced to the reactor along with the PMIDA. [00610] The material tested included:

(1) a 5%Pt/0.5% Fe on carbon support catalyst prepared generally in accordance with Wan et al. International Publication No. WO 2006/031938;

(2) a 50/50 (wt/wt) mixture of catalyst (1) and a 3% Co catalyst prepared as described in Example 27;

(3) catalyst (2) along w/ Bi₂C>₃ (2 mg) (500 ppm Bi, basis total reaction mass) ;

(4) a 50/50 (wt/wt) mixture of catalyst of the type (1) previously used in PMIDA oxidation testing under the conditions set forth above and a 3% Co catalyst prepared as described in Example 27.

[00611] Fig. 115 provides the time required to reach a predetermined endpoint of residual PMIDA concentration of less than approximately 500 ppm for each of the catalysts. As shown, the 5%Pt/0.5% Fe catalyst provided a reaction time of approximately 42 minutes while the mixture of the 5%Pt/0.5% Fe and 3% Co catalyst provided a reaction time of approximately 23 minutes. Addition of bismuth to this mixture increased the reaction time to approximately 28 minutes.

[00612] Table 43 shows HPLC results for the various product mixtures .

Table 43

[00613] As shown in Table 43, the catalyst mixture along with bismuth provided advantageous selectivity for PMIDA oxidation, and the presence of bismuth appeared to contribute to oxidation of formaldehyde and formic acid (based on a comparison the results for the mixture that did not include bismuth) .

Example 44

[00614] This example details testing of materials in PMIDA oxidation and monitoring generation of hydrogen.

[00615] A 3% cobalt catalyst prepared generally as described in Example 27 (2.85 g, 1.9% total reaction mass) was tested in a reactor including a total reaction mass (150 g) which included water (129.15 g) , 12% PMIDA (18.0 g) . The reaction was conducted at a temperature of approximately 100⁰C, a pressure of 60 psig, under an oxygen flow of approximately 100 cm³/min. Hydrogen generation was monitored during the reaction and results are shown in Fig. 116. Up to 1.6% (by volume) hydrogen was detected in the reaction off-gas.

[00616] After determining the amount of hydrogen generated, 5%Pt/0.5%Fe catalyst (0.15 g) was added the reaction mass to provide a mixture including the 3% Co catalyst and 5% Pt catalyst at a weight ratio of approximately 95:5, and a reaction mass including approximately 2 wt% catalyst material. Peak hydrogen generation for this mixture as shown in Fig. 116 was approximately 0.2%.

[00617] Bismuth oxide (1 mg, 7 ppm basis total reaction mass) was then added to the reaction mass including the mixture. Hydrogen generation results for this combination were similar to those for the mixture.

Example 45

[00618] A 50/50 (wt/wt) mixture of a 3% cobalt catalyst prepared generally as described in Example 27 and a 5%Pt/0.5%Fe catalyst prepared generally in accordance with Wan et al . International Publication No. WO 2006/031938 was tested in PMIDA oxidation under the following conditions: 1.8 wt % mixture, 14 wt% PMIDA, total reaction mass of 50Og. Testing was conducted under a pressure of 110 psig.

[00619] The temperature of the testing was varied during the first approximately 20 minutes of testing in accordance with the following schedule: 80⁰C for approximately 3 minutes; increase to approximately 90⁰C over the course of 4 minutes and hold for 3 minutes, increase to approximately 100⁰C over the course of 4 minutes and hold for approximately 3 minutes; increase to approximately 110⁰C over the course of 4 minutes and hold for the remainder of the testing.

[00620] The reaction was conducted to an endpoint determined as set forth in Example 26 to a residual PMIDA content of less than approximately 500 ppm. The reaction runtime was approximately 42 minutes.

[00621] The mixture was tested at various combinations of oxygen flow rate, manner of oxygen delivery, and/or addition of Bi₂θ3 at varying concentrations. 8 different combinations of catalyst/ mixture, oxygen flow rates, and/or Bi₂θ3 addition were tested:

(0) 5%Pt/0.5% Fe catalyst, initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(1) mixture, initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(2) mixture, initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(3) mixture, addition of Bi₂C>3 to provide Bi at a concentration of 2 ppm (total reaction mass) and initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(4) mixture, addition of Bi₂C>3 to provide Bi at a concentration of 5 ppm (total reaction mass) and initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(5) mixture, addition of Bi₂C>3 to provide Bi at a concentration of 5 ppm (total reaction mass) and initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(6) mixture, addition of Bi₂O₃ to provide Bi at a concentration of 10 ppm (total reaction mass) and initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(7) mixture, addition of Bi₂O₃ to provide Bi at a concentration of 10 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively, and utilizing dual frits for oxygen introduction; and

(8) repeat (6) .

[00622] Fig. 117 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00623] Fig. 118 shows residual PMIDA concentration.

[00624] Fig. 119 shows IDA selectivity.

[00625] Fig. 120 shows formaldehyde selectivity.

[00626] Fig. 121 shows formic acid selectivity. [00627] Fig. 122 shows N-methyl-N- (phosphonomethyl) glycine (NMG) selectivity.

[00628] Fig. 123 shows N-formylglyphosate (NFG) selectivity.

[00629] Fig. 124 shows glycine selectivity.

[00630] As shown in Figs. 120 and 121, incremental addition of bismuth improved formaldehyde and formic acid selectivity for the catalyst mixture. In addition, introducing Bi at a concentration of 10 ppm provided lower residual formic acid concentration than observed in connection with use of the 5%Pt/0.5%Fe catalyst alone.

Table 44

Example 46

[00631] This example details testing of a 5%Pt/0.5%Fe catalyst prepared generally in accordance with Wan et al . International Publication No. WO 2006/031938 and a 50/50 (wt/wt) mixture of a 3% cobalt catalyst prepared as described in Example 27 and the 5%Pt/0.5%Fe catalyst in PMIDA oxidation under the conditions set forth in Example 45. The platinum-containing catalyst was present in the reaction mass at a concentration of 0.9 wt% and the mixture was tested at a concentration of 1.8 wt% of the total reaction mass.

[00632] As in Example 45, addition of Bi₂C>3 to provide varying concentrations of Bi was also tested. The initial oxygen flow rate was 480 cm³/min and the final flow rate was 120 cmVrnin, and the point during the reaction at which the flow was reduced was selected to provide a reaction time of approximately 42 minutes. The conditions of the testing were as follows:

(0) 0.9 wt% 5%Pt/0.5%Fe catalyst, reduction of oxygen flow rate from 480 cm³/min to 120 cm³/min began after 23 minutes of reaction;

(1) 0.9 wt% 5%Pt/0.5%Fe catalyst, initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(2) 0.9 wt% 5%Pt/0.5%Fe catalyst, addition of Bi₂O₃ to provide Bi at a concentration of 250 ppm (total reaction mass), initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(3) 0.9 wt% 5%Pt/0.5%Fe catalyst, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass) , reduction of oxygen flow rate from 480 cm³/min to 120 cm³/min began after 23 minutes of reaction;

(4) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass) , reduction of oxygen flow rate from 480 cm³/min to 120 cm³/min began after 23 minutes of reaction;

(5) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(6) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 750 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(7) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 1000 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively; and

(8) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 1500 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively .

[00633] Fig. 125 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00634] Fig. 126 shows formaldehyde selectivity.

[00635] Fig. 127 shows formic acid selectivity.

[00636] Fig. 128 shows NMG selectivity.

[00637] Fig. 129 shows NFG selectivity.

[00638] Fig. 130 shows IDA selectivity.

[00639] Fig. 131 shows glycine selectivity.

[00640] A comparison of addition of Bi at concentrations of 500 ppm and 750 ppm indicate that residual formaldehyde content was similar, but the residual concentrations of formic acid, NMG, and NFG were lower with Bi addition at 750 ppm.

Example 47

[00641] This example details testing under the conditions and utilizing the catalysts and mixtures described in Examples 45 and 46 for the following combinations of conditions:

(0) 0.9 wt% 5%Pt/0.5%Fe catalyst, initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(1) 1.8 wt% mixture, initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(2) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(3) 1.8 wt% mixture, addition of Bi₂O₃ to provide Bi at a concentration of 750 ppm (total reaction mass), initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively; (4) 1.8 wt% mixture, addition of Bi₂θ3 to provide Bi at a concentration of 750 ppm (total reaction mass), initial and final oxygen flow rates of 320 cm³/min and 80 cm³/min, respectively; and

(5) 1.8 wt% mixture, addition of Bi₂C>3 to provide Bi at a concentration of 750 ppm (total reaction mass), initial and final oxygen flow rates of 400 cm³/min and 100 cm³/min, respectively .

[00642] Fig. 132 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00643] Fig. 133 shows formaldehyde selectivity.

[00644] Fig. 134 shows formic acid selectivity.

[00645] Fig. 135 shows NMG selectivity.

[00646] Fig. 136 shows NFG selectivity.

[00647] Fig. 137 shows IDA selectivity.

[00648] Fig. 138 shows glycine selectivity.

[00649] A comparison of the results for addition of Bi at concentrations of 750 ppm and 500 ppm indicate lower residual formic acid concentration for addition at 750 ppm, but higher residual formaldehyde concentration. Generally, reduction in initial and final oxygen flow rates provided reduced residual formaldehyde concentrations .

Example 48

[00650] This example details testing under the conditions and utilizing the catalysts and mixtures described in Examples 45 and 46 for the following combinations of conditions:

(0) 1.8 wt% 5%Pt/0.5%Fe catalyst, initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(1) 1.8 wt% 5%Pt/0.5%Fe catalyst, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass), initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(2) 1.8 wt% 5%Pt/0.5%Fe catalyst, addition of Bi₂O₃ to provide Bi at a concentration of 750 ppm (total reaction mass), initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively;

(3) 1.8 wt% 5%Pt/0.5%Fe catalyst, initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively; and

(4) 1.8 wt% 5%Pt/0.5%Fe catalyst, addition of Bi₂O₃ to provide Bi at a concentration of 500 ppm (total reaction mass), initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively .

[00651] Fig. 139 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00652] Fig. 140 shows formaldehyde selectivity.

[00653] Fig. 141 shows formic acid selectivity.

[00654] Fig. 142 shows NMG selectivity.

[00655] Fig. 143 shows NFG selectivity.

[00656] Fig. 144 shows IDA selectivity.

[00657] Fig. 145 shows glycine selectivity.

[00658] These results indicate a similar effect with addition of Bi at concentrations up to 750 ppm with a 5%Pt/0/5%Fe catalyst as observed and noted above with a catalyst mixture. Specifically, reduced residual formaldehyde and formic acid content, and reduced concentrations of NMG, NFG, IDA, and glycine .

Example 49

[00659] In preceding Examples 45-48 bismuth was provided by introduction of Bi₂O₃ in solid form along with the PMIDA. This compares addition of solid Bi₂O₃ and mixing the Bi₂O₃ in a liquid medium including PMIDA prior to introduction into the reactor. [00660] PMIDA oxidation was conducted under the conditions set forth above in Examples 45-48 with the following combination of catalysts described in these Examples, bismuth concentration, and oxygen flow rates :

(0) 1.8 wt% mixture, initial and final oxygen flow rates of 480 cmVrnin and 120 cm³/min, respectively;

(1) 1.8 wt% mixture, addition of Bi₂C>3 to provide Bi at a concentration of 500 ppm (total reaction mass), initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively .

[00661] Fig. 146 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00662] Fig. 147 shows formaldehyde selectivity.

[00663] Fig. 148 shows formic acid selectivity.

[00664] Fig. 149 shows NMG selectivity.

[00665] Fig. 150 shows NFG selectivity.

[00666] These results indicate similar performance with addition of a solid source of Bi and dilution of the Bi source prior to addition.

Example 50

[00667] This example details testing of use of tellurium in combination with a mixture of a platinum-containing catalyst and a cobalt-containing catalyst described in Examples 45-49 in PMIDA oxidation under the conditions set forth in Examples 45- 49. The combinations of catalyst, tellurium addition, and oxygen flow rates were as follows:

(1) 1.8 wt% mixture, addition of TeC>₂ to provide Te at a concentration of 391 ppm (total reaction mass), initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively;

(2) 1.8 wt% mixture, addition of TeO₂ to provide Te at a concentration of 764 ppm (total reaction mass) , initial and final oxygen flow rates of 480 cm³/min and 120 cm³/min, respectively .

[00668] Fig. 151 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00669] Fig. 152 shows formaldehyde selectivity.

[00670] Fig. 153 shows formic acid selectivity.

[00671] Fig. 154 shows NMG selectivity.

[00672] Fig. 155 shows NFG selectivity.

[00673] Fig. 156 shows IDA selectivity.

[00674] Fig. 157 shows glycine selectivity.

[00675] As shown, selectivity for each of the products shown in Figs. 152-157 generally decreased with increasing Te content, while the lower level of Te addition provided similar formaldehyde and formic acid selectivity to those noted above concerning addition of Bi.

Example 51

[00676] This example details testing of a mixture including a 3% Co catalyst prepared as detailed in Example 27 and a catalyst including 5%Pt/0.5%Fe catalyst prepared generally in accordance with Wan et al . International Publication No. WO 2006/031938 in PMIDA oxidation under the conditions described in Examples 45 and 46 for the following combinations of conditions:

(0) 1.8 wt% 5%Pt/0.5%Fe catalyst, initial and final oxygen flow rates of 320 cm³/min and 160 cm³/min, respectively; and

[00677] Fig. 158 shows total reaction time and the time at which reduction from the initial to final oxygen flow rate began .

[00678] Fig. 159 shows formaldehyde selectivity.

[00679] Fig. 160 shows formic acid selectivity.

[00680] Fig. 161 shows NMG selectivity.

[00681] Fig. 162 shows NFG selectivity.

[00682] Fig. 163 shows IDA selectivity.

[00683] Fig. 164 shows glycine selectivity.

[00684] Similar byproduct selectivities were achieved as compared to those noted above for the combination of a 5%Pt/0.5%Fe catalyst and 3% Co catalyst.

Example 52

[00685] This example provides results of testing of various promoters in conjunction with 1.5%Co catalyst prepared generally as described above. The catalyst/promoter combinations were tested in PMIDA oxidation generally under the conditions set forth in Example 26 to a fixed reaction time of 50 minutes. Carbon dioxide (CO₂) generation results are set forth in Table 46. Table 46

Table 46 First cycle results from 1.5%CoCN/C catalyst doped with promoters under 50 min fixed runtime*

[00686] This example also provide results of testing of various promoters in conjunction with 3%Co catalyst prepared generally as described above. The catalyst/promoter combinations were tested in PMIDA oxidation generally under the conditions set forth in Example 26 at a ΔECD value of 1.0. Runtime, CO₂ generation, and H₂ generation results are set forth in Table 47.

Example 53

[00687] This example provides results of testing of the combination of a 1.5%Co catalyst prepared generally as detailed above in combination with a titanium-containing zeolite (i.e., a TS-I titanium zeolite) . The combination was tested in PMIDA oxidation generally under the conditions set forth above. The results are shown in Table 48. Results of testing of the TS-I catalyst for oxidation of formic acid (FA) in the presence of hydrogen peroxide are shown in Table 49. Table 48

11.48g PMIDA, 20Og total reaction mass, 60psi, 100°C, 100 cc/min O₂ + 100 cc/min N₂ flow

Table 49

2g FA, 2g (lwt%) H₂O₂, 20Og total reaction mass, 60 psi, 100⁰C, 100 cc/min N₂ flow

******

[00688] The present invention is not limited to the above embodiments and can be variously modified. The above description of the preferred embodiments, including the Examples, is intended only to acquaint others skilled in the art with the invention, its principles, and its practical application so that others skilled in the art may adapt and apply the invention in its numerous forms, as may be best suited to the requirements of a particular use. [00689] With reference to the use of the word(s) comprise or comprises or comprising in this entire specification (including the claims below) , unless the context requires otherwise, those words are used on the basis and clear understanding that they are to be interpreted inclusively, rather than exclusively, and applicants intend each of those words to be so interpreted in construing this entire specification.

Claims

WHAT IS CLAIMED IS:

1. A process for the oxidation of an organic substrate, the process comprising: contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of a transition metal catalyst and a noble metal catalyst, wherein: transition metal catalyst comprises a transition metal composition on a carbon support, wherein the transition metal composition comprises a transition metal and nitrogen and the transition metal constitutes greater than 1% by weight of the transition metal catalyst; and the noble metal catalyst comprises a noble metal at a surface of a carbon support.

2. The process as set forth in claim 1 wherein the transition metal catalyst comprises an activated carbon support and the transition metal constitutes at least 1.6% by weight of the catalyst.

3. The process as set forth in claim 1 wherein the carbon support of the transition metal catalyst has a Langmuir surface area of from about 500 m²/g to about 2100 m²/g, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

4. A process as set forth in claim 1 wherein: the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A, the weighted molar average value of x being from about 0.5 to 2.0 and the weighted molar average value of y being from about 0.5 to about 8.0, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

5. The process as set forth in claim 1 wherein: the transition metal (M) constitutes greater than 2% by weight of the transition metal catalyst, and the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the transition metal catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A; the weighted molar average value of x being from about 0.5 to about 8 and the weighted molar average value of y being from about 0.5 to about 8.

6. The process as set forth in claim 5 wherein the weighted molar average value of x is from about 0.5 to 2.2.

7. The process as set forth in claim 1 wherein: the transition metal (M) is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof, and the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the transition metal catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A, wherein the relative abundance of ions in which x is 1 is at least 42%.

8. The process as set forth in claim 1 wherein the micropore Langmuir surface area of said transition metal catalyst is at least about 70% of the micropore Langmuir surface area of said carbon support of said transition metal catalyst prior to formation of said transition metal composition thereon, and the transition metal constitutes at least 1.6% by weight of the catalyst.

9. The process as set forth in claim 1 wherein the transition metal constitutes at least about 2% by weight of the transition metal catalyst, and the micropore Langmuir surface area of said transition metal catalyst is from about 60^ to less than 80% of the micropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

10. The process as set forth in claim 1 wherein the transition metal constitutes from about 2% to less than 5% by weight of the transition metal catalyst, and the micropore Langmuir surface area of said transition metal catalyst is at least about 60% of the micropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

11. The process as set forth in claim 1 wherein: the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the transition metal constitutes at least about 2% by weight of the transition metal catalyst; and the total Langmuir surface area of said transition metal catalyst is at least about 60% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

12. The process as set forth in claim 1 wherein: the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the total Langmuir surface area of said transition metal catalyst is less than about 2000 m²/g; the total Langmuir surface area of said transition metal catalyst is at least about 75% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon; and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

13. The process as set forth in claim 1 wherein: the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; the transition metal constitutes at least about 2% by weight of the transition metal catalyst; the total Langmuir surface area of said transition metal catalyst is less than about 2000 m²/g; and the total Langmuir surface area of said transition metal catalyst is at least about 60% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

14. The process as set forth in any one of claims 1 to 13 wherein the organic substrate is contacted with the oxidizing agent in the presence of the transition metal catalyst, the noble metal catalyst, and a supplemental promoter.

15. A process for the oxidation of an organic substrate, the process comprising: contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of a supplemental promoter, a transition metal catalyst, and a noble metal catalyst, wherein: the transition metal catalyst comprises a transition metal composition on a carbon support, wherein the transition metal composition comprises a transition metal and nitrogen; and the noble metal catalyst comprises a noble metal at a surface of a carbon support.

16. The process as set forth in any one of claims 1 to 15 wherein the transition metal catalyst is introduced into a liquid reaction medium comprising the organic substrate and the noble metal catalyst.

17. The process as set forth in claim 16 wherein the liquid reaction medium into which the transition metal catalyst is introduced further comprises the supplemental promoter.

18. The process as set forth in any one of claims 1 to 15 wherein the noble metal catalyst is introduced into a liquid reaction medium comprising the organic substrate and the transition metal catalyst.

19. The process as set forth in claim 18 wherein the liquid reaction medium into which the noble metal catalyst is introduced further comprises the supplemental promoter.

20. The process as set forth in claim 14 or 15 wherein the supplemental promoter is introduced into a liquid reaction medium comprising the organic substrate and the noble metal catalyst .

21. The process as set forth in claim 14 or 15 wherein the supplemental promoter is introduced into a liquid reaction medium comprising the organic substrate and the transition metal catalyst .

22. The process as set forth in any one of claims 1 to 15 wherein a catalyst mixture comprised by the transition metal catalyst and noble metal catalyst is introduced into a liquid reaction medium comprising the organic substrate.

23. The process as set forth in claim 22 wherein the supplemental promoter is introduced into the liquid reaction medium comprising the catalyst mixture and the organic substrate .

24. The process as set forth in any one of claims 1 to 23 wherein the noble metal catalyst has been used in one or more previous oxidation reactions.

25. The process as set forth in any one of claims 1 to 24 wherein the transition metal catalyst has been used in one or more previous oxidation reactions.

26. The process as set forth in any one of claims 14 to 25 wherein the supplemental promoter comprises a metal or a metal compound, and the weight ratio of the metal or metal compound to the transition metal catalyst in the liquid reaction medium is at least about 1:2500, at least about 1:2000, at least about 1:1500, or at least about 1:1000.

27. The process as set forth in any one of claims 14 to 25 wherein the supplemental promoter comprises a metal or a metal compound, and the weight ratio of the metal or metal compound to the transition metal catalyst in the reaction medium is less than about 1:10000, less than about 1:8000, less than about 1:6000, or less than about 1:4000.

28. The process as set forth in any one of claims 14 to 27 wherein the supplemental promoter comprises a metal or a metal compound, and the weight ratio of the metal or metal compound to the noble metal catalyst in the reaction medium is at least about 1:2500, at least about 1:2000, at least about 1:1500, or at least about 1:1000.

29. The process as set forth in any one of claims 14 to 27 wherein the supplemental promoter comprises a metal or a metal compound, and the weight ratio of the metal or metal compound to the noble metal catalyst in the reaction medium is less than about 1:10000, less than about 1:8000, less than about 1:6000, or less than about 1:4000.

30. The process as set forth in any one of claims 1 to 29 wherein the weight ratio of transition metal catalyst to noble metal catalyst in the reaction medium is at least about 0.1:1, at least about 0.5:1, or at least about 1:1.

31. The process as set forth in any one of claims 1 to 30 wherein the weight ratio of transition metal catalyst to noble metal catalyst in the reaction medium is from about 0.1:1 to about 20:1, from about 0.5:1 to about 10:1, from about 0.75:1 to about 5:1, or about 1:1.

32. The process as set forth in any one of claims 1 to 31 wherein the organic substrate and oxidizing agent are contacted in a reaction zone.

33. The process as set forth in any one of claims 14 to 32 wherein the organic substrate and oxidizing agent are contacted in a reaction zone comprising a flow reaction zone that is not substantially axially backmixed, and the supplemental promoter is introduced to the reaction zone along with the organic substrate .

34. The process as set forth in any one of claims 14 to 32 wherein the organic substrate and oxidizing agent are contacted in a reaction zone comprising a flow reaction zone that is not substantially axially backmixed, and the supplemental promoter is added to the reaction zone at a point downstream from addition of the organic substrate.

35. The process as set forth in any one of claims 14 to 34 wherein the organic substrate and oxidizing agent are contacted in multiple reaction zones in series, wherein the supplemental promoter is introduced into the first reaction zone in the series.

36. The process as set forth in any one of claims 14 to 35 wherein the organic substrate and oxidizing agent are contacted in a series of multiple reaction zones, wherein the supplemental promoter is introduced into a reaction zone other than the first in the series.

37. The process as set forth in claim 35 or 36 wherein each of said multiple reaction zones of said series is provided by continuous stirred tank reactors.

38. The process as set forth in any one of claims 32 to 37 further comprising: withdrawing a reaction mixture effluent from a reaction zone; separating transition metal catalyst and noble metal catalyst from the reaction mixture effluent; and introducing the supplemental promoter, used transition metal catalyst, and used noble metal catalyst to a reaction zone wherein a further quantity of an oxidation reaction substrate is contacted with an oxidizing agent in the presence of said catalysts and said supplemental promoter.

39. The process as set forth in any one of claims 1 to 38 wherein the transition metal catalyst is particulate.

40. The process as set forth in any one of claims 1 to 39 wherein the transition metal catalyst is slurried in the reaction medium.

41. The process as set forth in any one of claims 1 to 40 wherein the noble metal catalyst is particulate.

42. The process as set forth in any one of claims 1 to 41 wherein the noble metal catalyst is slurried in the reaction medium.

43. The process as set forth in any one of claims 14 to 42 wherein the supplemental promoter is particulate.

44. The process as set forth in any one of claims 14 to 43 wherein the supplemental promoter is slurried in the reaction medium.

45. The process as set forth in any one of claims 14 to 44 wherein the supplemental promoter is mixed with a liquid medium to provide a supplemental promoter mixture that is introduced into the liquid reaction medium.

46. The process as set forth in claim 45 wherein the liquid medium with which the supplemental promoter is mixed comprises the organic substrate.

47. The process as set forth in any one of claims 14 to 46 wherein the supplemental promoter comprises a metal selected from the group consisting of bismuth, lead, germanium, tellurium, titanium, copper, nickel, and combinations thereof.

48. The process as set forth in claim 47 wherein the supplemental promoter comprises bismuth.

49. The process as set forth in claim 48 wherein bismuth is introduced into the reaction medium in the form of bismuth oxide, bismuth hydroxide, bismuth chloride, bismuth bromide, bismuth iodide, bismuth sulphide, bismuth selenide, bismuth telluride, bismuth sulphite, bismuth sulphate, bismuthyl sulfate, bismuthyl nitrite, bismuth nitrate, bismuthyl nitrate, double nitrate of bismuth and magnesium, bismuth phosphite, bismuth phosphate, bismuth pyrophosphate, bismuthyl carbonate, bismuth perchlorate, bismuth antimonate, bismuth arsenate, bismuth selenite, bismuth titanate, bismuth vanadate, bismuth niobate, bismuth tantalate, bismuth chromate, bismuthyl dichromate, bismuthyl chromate, double chromate of bismuthyl and potassium, bismuth molybdate, double molybdate of bismuth and sodium, bismuth tungstate, bismuth permanganate, bismuth zirconate, bismuth acetate, bismuthyl propionate, bismuth benzoate, bismuthyl salicylate, bismuth oxalate, bismuth tartrate, bismuth lactate, bismuth citrate, bismuth gallate, bismuth pyrogallate, bismuth phosphide, bismuth arsenide, sodium bismuthate, bismuth-thiocyanic acid, sodium salt of bismuth- thiocyanic acid, potassium salt bismuth-thiocyanic acid, trimethylbismuthine, triphenylbismuthine, bismuth oxychloride, or bismuth oxyiodide.

50. The process as set forth in claim 49 wherein bismuth is introduced into the liquid medium in the form of Bi₂C>3.

51. The process as set forth in claim 47 wherein the supplemental promoter comprises tellurium.

52. The process as set forth in claim 47 wherein tellurium is introduced into the reaction medium in the form of a tellurium oxide, a tellurium chloride, a tellurium fluoride, a tellurium bromide, a tellurium iodide, a tellurium dioxide or a tellurium nitrate.

53. The process as set forth in claim 52 wherein tellurium is introduced into the liquid medium in the form of TeO₂.

54. The process as set forth in claim 52 wherein tellurium is introduced into the liquid medium in the form of TeCl₄.

55. The process as set forth in claim 52 wherein tellurium is introduced into the liquid medium in the form of Te(OH)₆.

56. The process as set forth in any one of claims 14 to 55 wherein the reaction medium is contacted with the oxidizing agent in the presence of at least two supplemental promoters.

57. The process as set forth in claim 56 wherein the at least two supplemental promoters comprise bismuth and tellurium.

58. The process as set forth in any one of claims 14 to 57 wherein the supplemental or at least two supplemental promoters reduce noble metal leaching from the carbon support of the noble metal catalyst.

59. The process as set forth in any one of claims 1 to 58 wherein the oxidizing agent is contacted with the reaction medium at an initial oxygen flow rate and a final oxygen flow rate .

60. The process as set forth in claim 59 wherein the reaction medium is contacted with the oxidizing agent in the presence of the transition metal catalyst, the noble metal catalyst, and a supplemental promoter.

61. The process as set forth in claim 59 or 60 wherein the final oxygen flow rate is no more than about 50%, no more than about 40%, no more than about 30%, no more than about 20%, or no more than about 10% of the initial oxygen flow rate.

62. The process as set forth in any one of claims 59 to 61 wherein the initial oxygen flow rate is from about 0.1 to about 2, from about 0.25 to about 1.5, or from about 0.5 to about 1 m³/minute per m³ reaction medium.

63. The process as set forth in any one of claims 59 to 62 wherein the final oxygen flow rate is from about 0.05 to about

1, from about 0.1 to about 0.75, or from about 0.2 to about 0.5 m³/minute per m³ reaction medium.

64. The process as set forth in any one of claims 59 to 63 wherein the initial oxygen flow rate is from about 0.1 to about

2, from about 0.25 to about 1.5, or from about 0.5 to about 1 m³/minute per kg transition metal catalyst.

65. The process as set forth in any one of claims 59 to 64 wherein the final oxygen flow rate is from about 0.05 to about 1, from about 0.2 to about 0.75, or from about 0.2 to about 0.5 mVminute per kg transition metal catalyst.

66. The process as set forth in any one of claims 59 to 65 wherein the initial oxygen flow rate is from about 0.1 to about

2, from about 0.25 to about 1.5, or from about 0.5 to about 1 mVminute per kg noble metal metal catalyst.

67. The process as set forth in any one of claims 59 to 66 wherein the final oxygen flow rate is from about 0.05 to about 1, from about 0.2 to about 0.75, or from about 0.2 to about 0.5 mVminute per kg noble metal catalyst.

68. The process as set forth in any one of claims 59 to 67 wherein the initial oxygen flow rate is from about 0.001 to about 0.01, from about 0.002 to about 0.01, or from about 0.004 to about 0.01 mVminute per initial kg organic substrate.

69. The process as set forth in any one of claims 59 to 68 wherein the final oxygen flow rate is from about 0.001 to about 0.005, from about 0.001 to about 0.004, or from about 0.001 to about 0.003 mVminute per kg organic substrate.

70. The process as set forth in any one of claims 59 to 69 comprising a transition point during said contacting at which substantial conversion of the PMIDA substrate is achieved.

71. The process as set forth in any one of claims 59 to 70 comprising a transition point during said contacting at which the concentration of organic substrate in the reaction medium is no more than about 10% by weight, no more than about 8% by weight, no more than about 6% by weight, no more than about 4% by weight, or no more than about 2% by weight.

72. The process as set forth in any one of claims 59 to 71 comprising a transition point during said contacting at which the concentration of organic substrate in the reaction medium is from about 0.5% to about 10% by weight, from about 1% to about 8% by weight, from about 1% to about 6% by weight, from about 1% to about 4%, or from about 1% to about 3% by weight.

73. The process as set forth in any one of claims 59 to 72 comprising a transition point during said contacting at which an organic substrate conversion of at least about 70%, at least about 75%, at least about 80%, or at least about 85% is achieved.

74. The process as set forth in any one of claims 59 to 73 comprising a transition point during said contacting at which an organic substrate conversion of from about 70% to about 95%, from about 75% to about 90%, or from about 80% to about 95% is achieved.

75. The process as set forth in any one of claims 1 to 74 wherein the organic substrate is selected from the group consisting of alcohols, aldehydes, tertiary amines, secondary amines, acids, and combinations thereof.

76. A process as set forth in claim 75 wherein said substrate comprises a tertiary amine which is oxidized to a secondary amine.

77. A process as set forth in claim 76 wherein said substrate corresponds to a compound of Formula II having the structure :

[Formula II] wherein R¹ is selected from the group consisting of R⁵OC(O)CH₂- and R⁵OCH₂CH₂-, R² is selected from the group consisting of R⁵OC(O)CH₂-, R⁵OCH₂CH₂-, hydrocarbyl, substituted hydrocarbyl, acyl, -CHR⁶PO₃R⁷R⁸, and -CHR⁹SO₃R¹⁰, R⁶, R⁹ and R¹¹ are selected from the group consisting of hydrogen, alkyl, halogen and -NO₂, and R³, R⁴, R⁵, R⁷, R⁸ and R¹⁰ are independently selected from the group consisting of hydrogen, hydrocarbyl, substituted hydrocarbyl and a metal ion .

78. A process as set forth in claim 77 wherein R¹ comprises R⁵OC(O)CH₂-, R¹¹ is hydrogen, and R⁵ is selected from hydrogen and an agronomically acceptable cation.

79. A process as set forth in claim 78 wherein R² is selected from the group consisting of R⁵OC(O)CH₂-, acyl, hydrocarbyl and substituted hydrocarbyl.

80. A process as set forth in claim 77 wherein said substrate comprises N- (phosphonomethyl) iminodiacetic acid or a salt thereof and is oxidized to form N- (phosphonomethyl) glycine or a salt thereof.

81. A process as set forth in claim 80 wherein said oxidation catalyst is effective for oxidation of byproduct formaldehyde produced in the oxidation of N- (phosphonomethyl) iminodiacetic acid or a salt thereof.

82. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein: the transition metal catalyst comprises a transition metal composition on a carbon support, wherein the transition metal composition comprises a transition metal and nitrogen and the transition metal constitutes greater than 1% by weight of the transition metal catalyst; and the noble metal catalyst comprises a noble metal at a surface of a carbon support.

83. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises an activated carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, wherein the transition metal constitutes at least 1.6% by weight of the catalyst.

84. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, the carbon support of the transition metal catalyst has a

Langmuir surface area of from about 500 m²/g to about 2100 m²/g, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

85. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal (M) and nitrogen, wherein: the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A, the weighted molar average value of x being from about 0.5 to 2.0 and the weighted molar average value of y being from about 0.5 to about 8.0, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

86. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a transition metal composition comprising a transition metal (M) and nitrogen, wherein: the transition metal (M) constitutes greater than 2% by weight of the transition metal catalyst; and the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the transition metal catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in

Protocol A; the weighted molar average value of x being from about 0.5 to about 8 and the weighted molar average value of y being from about 0.5 to about 8.

87. A mixture as set forth in claim 86 wherein the weighted molar average value of x is from about 0.5 to 2.2.

88. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a transition metal composition comprising a transition metal (M) and nitrogen, wherein: the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof; and the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xC_y ⁺ when the transition metal catalyst is analyzed by Time-of-Flight

Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A, wherein the relative abundance of ions in which x is 1 is at least 42%.

89. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, wherein: the micropore Langmuir surface area of said transition metal catalyst is at least about 70% of the micropore Langmuir surface area of said carbon support of said transition metal catalyst prior to formation of said transition metal composition thereon, and the transition metal constitutes at least 1.6% by weight of the catalyst.

90. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a transition metal composition comprising a transition metal and nitrogen, wherein: the transition metal constitutes at least about 2% by weight of the transition metal catalyst, and the micropore Langmuir surface area of said transition metal catalyst is from about 60% to less than 80% of the micropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

91. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, wherein: the transition metal constitutes from about 2% to less than 5% by weight of the transition metal catalyst, and the micropore Langmuir surface area of said transition metal catalyst is at least about 60% of the micropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon .

92. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, the transition metal being selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof, wherein : the transition metal constitutes at least about 2% by weight of the transition metal catalyst, and the total Langmuir surface area of said transition metal catalyst is at least about 60% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

93. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a carbon support having formed thereon a transition metal composition comprising a transition metal and nitrogen, the transition metal being selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof, wherein : the total Langmuir surface area of said transition metal catalyst is less than about 2000 m²/g, the total Langmuir surface area of said transition metal catalyst is at least about 75% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon, and the transition metal constitutes at least 1.6% by weight of the transition metal catalyst.

94. A mixture comprising a transition metal catalyst and a noble metal catalyst, wherein the transition metal catalyst comprises a transition metal composition comprising a transition metal and nitrogen, the transition metal being selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, cerium, and combinations thereof, wherein: the transition metal constitutes at least about 2% by weight of the transition metal catalyst, the total Langmuir surface area of said transition metal catalyst is less than about 2000 m²/g, and the total Langmuir surface area of said transition metal catalyst is at least about 60% of the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

95. The mixture of any of claims 82 to 94 further comprising a supplemental promoter.

96. A catalyst system comprising a liquid medium having a transition metal catalyst, a noble metal catalyst, and a supplemental promoter dispersed therein, wherein: the transition metal catalyst comprises a transition metal composition on a carbon support, wherein the transition metal composition comprises a transition metal and nitrogen; and the noble metal catalyst comprises a noble metal at a surface of a carbon support.

97. The mixture or system as set forth in claim 95 or 96 wherein the supplemental promoter comprises a metal selected from the group consisting of bismuth, lead, germanium, tellurium, titanium, copper, nickel, and combinations thereof.

98. The mixture or system as set forth in claim 97 wherein the supplemental promoter comprises bismuth.

99. The mixture or system as set forth in 97 wherein the supplemental promoter comprises tellurium.

100. The mixture or system as set forth in claim 95 or 96 comprising at least two supplemental promoters.

101. The mixture or system as set forth in claim 100 wherein the at least two supplemental promoters comprise bismuth and tellurium.

102. The mixture or system as set forth in any one of claims 97 to 101 wherein bismuth is provided by a metal compound comprising bismuth oxide, bismuth hydroxide, bismuth chloride, bismuth bromide, bismuth iodide, bismuth sulphide, bismuth selenide, bismuth telluride, bismuth sulphite, bismuth sulphate, bismuthyl sulfate, bismuthyl nitrite, bismuth nitrate, bismuthyl nitrate, double nitrate of bismuth and magnesium, bismuth phosphite, bismuth phosphate, bismuth pyrophosphate, bismuthyl carbonate, bismuth perchlorate, bismuth antimonate, bismuth arsenate, bismuth selenite, bismuth titanate, bismuth vanadate, bismuth niobate, bismuth tantalate, bismuth chromate, bismuthyl dichromate, bismuthyl chromate, double chromate of bismuthyl and potassium, bismuth molybdate, double molybdate of bismuth and sodium, bismuth tungstate, bismuth permanganate, bismuth zirconate, bismuth acetate, bismuthyl propionate, bismuth benzoate, bismuthyl salicylate, bismuth oxalate, bismuth tartrate, bismuth lactate, bismuth citrate, bismuth gallate, bismuth pyrogallate, bismuth phosphide, bismuth arsenide, sodium bismuthate, bismuth-thiocyanic acid, sodium salt of bismuth- thiocyanic acid, potassium salt bismuth-thiocyanic acid, trimethylbismuthine, triphenylbismuthine, bismuth oxychloride, bismuth oxyiodide, or a combination thereof.

103. The mixture or system as set forth in claim 102 wherein bismuth is provided by Bi₂C>₃.

104. The mixture or system as set forth in any one of claims 97 to 103 wherein tellurium is provided by a metal compound comprising a tellurium oxide, a tellurium chloride, a tellurium fluoride, a tellurium bromide, a tellurium iodide, a tellurium dioxide, a tellurium nitrate, or a combination thereof .

105. The system as set forth in claim 104 wherein tellurium is provided by TeO₂, TeCl₄, Te(OH)₆, or a combination thereof.

106. The mixture or system as set forth in any one of claims 82 to 105 wherein the transition metal catalyst is in particulate form.

107. The mixture or system as set forth in any one or claims 82 to 106 wherein the transition metal catalyst is in powder form.

108. The mixture or system as set forth in any one of claims 82 to 107 wherein the noble metal catalyst is in particulate form.

109. The mixture or system as set forth in any one of claims 82 to 108 wherein the noble metal catalyst is in powder form.

110. The mixture or system as set forth in any one of claims 97 to 109 wherein the supplemental promoter is in particulate form.

111. The mixture or system as set forth in any one of claims 97 to 110 wherein the supplemental promoter is in powder form.

112. The mixture or system as set forth in any one of claims 97 to 111 wherein the weight ratio of supplemental promoter to transition metal catalyst is at least about 0.0001:1, at least about 0.001:1, or at least about 0.01:1.

113. The mixture or system as set forth in any one of claims 97 to 112 wherein the supplemental promoter comprises a metal or a metal compound, and the weight ratio of the metal or metal compound to the transition metal catalyst is from about 0.0001:1 to about 2.5:1, from about 0.001:1 to about 1:1, or from about 0.01:1 to about 0.5:1.

114. The mixture or system as set forth in any one of claims 97 to 113 wherein the supplemental promoter comprises a metal or metal compound, and the weight ratio of the metal or metal compound to the noble metal catalyst is at least about 0.0001:1, at least about 0.001:1, or at least about 0.01:1.

115. The mixture or system as set forth in any one of claims 82 to 114 wherein the weight ratio of the metal or metal compound to the noble metal catalyst is from about 0.0001:1 to about 2.5:1, from about 0.001:1 to about 1:1, or from about 0.01:1 to about 0.5:1.

116. The mixture or system as set forth in any one of claims 82 to 115 wherein the weight ratio of transition metal catalyst to noble metal catalyst is from about 0.1:1 to about 20:1, from about 0.2:1 to about 15:1, from about 0.3:1 to about 10:1, from about 0.5:1 to about 5:1, from about 0.75:1 to about 2.5:1, or about 1:1.

117. The process, mixture or system as set forth in any one of claims 1 to 116 wherein the carbon support of the transition metal catalyst comprises activated carbon.

118. The process, mixture or system as set forth in any one of claims 1 to 117 wherein the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon is at least about 1000 m²/g.

119. The process, mixture or system as set forth in any one of claims 1 to 118 wherein the total Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon is from about 1000 m²/g to about 1600 m²/g.

120. The process, mixture or system as set forth in any one of claims 1 to 119 wherein the transition metal catalyst has a total Langmuir surface area of at least about 600 m²/g.

121. The process, mixture or system as set forth in any one of claims 1 to 120 wherein the transition metal catalyst has a total Langmuir surface area of from about 600 m²/g to about 1400 m²/g.

122. The process, mixture or system as set forth in any one of claims 1 to 121 wherein the total Langmuir surface area of said transition metal catalyst is at least about 60% of the total Langmuir surface area of said carbon support of the transition metal composition prior to formation of said transition metal composition thereon.

123. The process, mixture or system as set forth in any one of claims 1 to 122 wherein the total Langmuir surface area of said transition metal catalyst is from about 60% to about 80% of the total Langmuir surface area of said carbon support of the transition metal composition prior to formation of said transition metal composition thereon.

124. The process, mixture or system as set forth in any of claims 1 to 123 wherein the micropore Langmuir surface area of said transition metal catalyst is at least about 750 m²/g.

125. The process, mixture or system as set forth in any one of claims 1 to 124 wherein the micropore Langmuir surface area of said transition metal catalyst is from about 750 m²/g to about 1100 m²/g.

126. The process, mixture or system as set forth in any one of claims 1 to 125 wherein the micropore Langmuir surface area of said transition metal catalyst is at least about 55% of said transition metal composition thereon.

127. The process, mixture or system as set forth in any one of claims 1 to 126 wherein the micropore Langmuir surface area of said transition metal catalyst is from about 55% to about 80% of said carbon support prior to formation of said transition metal composition thereon.

128. The process, mixture or system as set forth in any one of claims 1 to 127 wherein the combined mesopore and macropore Langmuir surface area of said transition metal catalyst is at least about 175 m²/g.

129. The process, mixture or system as set forth in any one of claims 1 to 128 wherein the combined mesopore and macropore Langmuir surface area of said transition metal catalyst is from about 175 to about 300 m²/g.

130. The process, mixture or system as set forth in any one of claims 1 to 129 wherein the combined mesopore and macropore Langmuir surface area of said transition metal catalyst is at least about 70% of the combined mesopore and macropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon .

131. The process, mixture or system as set forth in any one of claims 1 to 130 wherein the combined mesopore and macropore Langmuir surface area of said transition metal catalyst is from about 70% to about 90% of the combined mesopore and macropore Langmuir surface area of said carbon support of the transition metal catalyst prior to formation of said transition metal composition thereon.

132. The process, mixture or system as set forth in any one of claims 1 to 131 wherein the transition metal constitutes at least 0.5%, at least 1.0%, or at least 1.5% by weight of the transition metal catalyst.

133. The process, mixture or system as set forth in any one of claims 1 to 132 wherein the transition metal constitutes at least 1.6%, at least 1.8%, or at least about 2.0% by weight of the transition metal catalyst.

134. The process, mixture or system as set forth in any one of claims 1 to 133 wherein the transition metal constitutes about 3% by weight of the transition metal catalyst.

135. The process, mixture or system as set forth in any one of claims 1 to 134 wherein the transition metal constitutes less than about 10% by weight of the catalyst or less than about 5% by weight of the transition metal catalyst.

136. The process, mixture or system as set forth in any one of claims 1 to 135 wherein the transition metal constitutes between 1.6% and 5% by weight of the catalyst or between 2% and 5% by weight of the transition metal catalyst.

137. The process, mixture or system as set forth in any one of claims 1 to 136 wherein the transition metal constitutes from about 0.5% to about 3.0%, from about 1% to about 3%, or from about 1.5% to about 3% by weight of the transition metal catalyst.

138. The process, mixture or system as set forth in any one of claims 1 to 137 wherein said nitrogen of said transition metal composition formed on said carbon support of the transition metal catalyst is present in a proportion of at least about 0.1% by weight of the transition metal catalyst.

139. The process, mixture or system as set forth in any one of claims 1 to 138 wherein said nitrogen of said transition metal composition formed on said carbon support of the transition metal composition is present in a proportion of from about 0.1% to about 20% by weight of the transition metal catalyst .

140. The process, mixture or system as set forth in any one of claims 1 to 139 wherein the transition metal composition further comprises carbon.

141. The process, mixture or system as set forth in any one of claims 1 to 140 wherein the transition metal composition comprises a transition metal nitride, a transition metal carbide, a transition metal carbide-nitride, or a combination thereof.

142. The process, mixture or system as set forth in claim 141 wherein the transition metal composition comprises a transition metal nitride.

143. The process, mixture or system as set forth in any one of claims 1 to 142 wherein the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ when the catalyst is analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF SIMS) as described in Protocol A.

144. The process, mixture or system as set forth in claim 143 wherein the weighted molar average value of x is from about 0.5 to about 8.0, from about 0.5 to about 5.0, from about 0.5 to about 3.5, from about 0.5 to about 3.0, from about 0.5 to about 2.20, or from about 0.5 to about 2.10.

145. The process, mixture or system as set forth in claim 143 wherein the weighted molar average value of x is from about 1.0 to about 8.0, from about 1.0 to about 5.0, from about 1.0 to about 3.0, from about 1.0 to about 2.10, from about 1.0 to about 2.0, or from about 1.5 to about 2.0.

146. The process, mixture or system as set forth in any one of claims 143 to 145 wherein the weighted molar average value of y is from about 0.5 to about 5.0, from about 1.0 to about 5.0, from about 1.0 to about 4.0, from about 1.0 to about 3.0, from about 1.0 to about 2.6, from about 1.0 to about 2.0, from about 1.5 to about 2.6, or from about 2.0 to about 2.6.

147. The process, mixture or system as set forth in any one of claims 1 to 146 wherein the transition metal catalyst characterized as generating ions corresponding to the formula MN_xCy⁺ during said ToF SIMS analysis as described in Protocol A and MN_xCy⁺ ions in which the weighted molar average value of x is from 4.0 to about 8.0 constitute no more than about 60 mole percent of said MN_xCy⁺ ions generated, no more than about 50 mole percent, no more than about 40 mole percent, no more than about 25 mole percent, no more than about 20 mole percent, no more than about 15 mole percent, or no more than about 10 mole percent of said MN_xCy⁺ ions.

148. The process, mixture or system as set forth in any one of claims 1 to 147 wherein the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ during said ToF SIMS analysis as described in Protocol A and the relative abundance of ions in which x is 1 is at least about 5%, at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, or at least about 35%, at least about 42%, at least about 45%, or at least about 50%.

149. The process, mixture or system as set forth in claim 148 wherein the relative abundance of ions in which x is 1 is at less than about 90%, less than about 85%, or less than about 75.

150. The process, mixture or system as set forth in any one of claims 1 to 149 wherein the transition metal catalyst is characterized as generating ions corresponding to the formula MN_xCy⁺ during said ToF SIMS analysis as described in Protocol A and the relative abundance of ions in which x is 1 and y is 1 is at least about 10%, at least about 15%, at least about 20%, at least about 25%, at least about 30%, or at least about 35%.

151. The process, mixture or system as set forth in claim 150 wherein the relative abundance of ions in which x is 1 and y is 1 is from about 10% to about 40%, from about 15% to about 35%, or from about 20% to about 30%.

152. The process, mixture or system as set forth in any one of claims 1 to 151 wherein the transition metal is a transition metal other than a platinum group metal.

153. The process, mixture or system as set forth in claim 152 wherein the transition metal is a transition metal other than platinum or palladium.

154. The process, mixture or system as set forth in claim 152 wherein the transition metal is a transition metal other than platinum.

155. The process, mixture or system as set forth in any one of claims 1 to 154 wherein the transition metal is selected from the group consisting of Group IB, Group VB, Group VIB, Group VIIB, Group VIII, lanthanide series metals, and combinations thereof.

156. The process, mixture or system as set forth in claim 155 wherein the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, iron, cobalt, nickel, ruthenium, cerium, and combinations thereof.

157. The process, mixture or system as set forth in any one of claims 1 to 156 wherein the transition metal is selected from the group consisting of chromium, iron, cobalt, and combinations thereof .

158. The process, mixture or system as set forth in claim 157 wherein the transition metal comprises iron.

159. The process, mixture or system as set forth in claim 157 wherein the transition metal comprises cobalt.

160. The process, mixture or system as set forth in any one of claims 1 to 155 wherein the transition metal is selected from the group consisting of copper, silver, vanadium, chromium, molybdenum, tungsten, manganese, cobalt, nickel, ruthenium, cerium, and combinations thereof.

161. The process, mixture or system as set forth in claim 160 wherein said transition metal comprises chromium.

162. The process, mixture or system as set forth in claim 160 wherein said transition metal comprises cobalt.

163. The process, mixture or system as set forth in any one of claims 1 to 162 wherein the transition metal catalyst is characterized by its effectiveness for catalyzing the oxidation of formaldehyde such that when a representative aqueous solution having a pH of about 1.5 and containing 0.8% by weight formaldehyde and 0.11% by weight of said transition metal catalyst is agitated and sparged with molecular oxygen at a rate of 0.75 cm³ oxygen/minute/gram aqueous mixture at a temperature of about 100⁰C and pressure of about 60 psig, at least about 5%, at least about 10%, at least about 15%, at least about 20%, or at least about 30% of said formaldehyde is converted to formic acid, carbon dioxide and/or water.

164. The process, mixture or system as set forth in any one of claims 1 to 163 wherein the transition metal catalyst is characterized by its effectiveness for catalyzing the oxidation of formaldehyde such that when a representative aqueous solution having a pH of about 1.5 and containing 0.8% by weight formaldehyde, 5.74% by weight N- (phosphonomethyl) iminodiacetic acid, and 0.11% by weight of said transition metal catalyst is agitated and sparged with molecular oxygen at a rate of 0.75 cm³ oxygen/minute/gram aqueous mixture at a temperature of about 100⁰C and pressure of about 60 psig, at least about 50%, at least about 60%, at least about 70%, at least about 80%, or at least about 90% of said formaldehyde is converted to formic acid, carbon dioxide and/or water.

165. The process, mixture or system as set forth in any one of claims 1 to 164 wherein the transition metal comprises cobalt and the transition metal catalyst is characterized such that the catalyst exhibits at least about 0.50 x 10²⁵ spins/mole cobalt, at least about 1.0 x 10²⁵ spins/mole cobalt, at least about 1.0 x 10²⁵ spins/mole cobalt, at least about 2.0 x 10²⁵ spins/mole cobalt, or at least about 2.50 x 10²⁵ spins/mole cobalt when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B.

166. The process, mixture or system as set forth in any one of claims 1 to 165 wherein the transition metal comprises cobalt and the transition metal catalyst is characterized such that the catalyst exhibits at least about 3.00 x 10²⁵ spins/mole cobalt, at least about 3.50 x 10²⁵ spins/mole cobalt, at least about 4.50 x 10²⁵ spins/mole cobalt, at least about 5.50 x 10²⁵ spins/mole cobalt, at least about 6.50 x 10²⁵ spins/mole cobalt, at least about 7.50 x 10²⁵ spins/mole cobalt, at least about 8.50 x 10²⁵ spins/mole cobalt, or at least about 9.50 x 10²⁵ when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B.

167. The process, mixture or system as set forth in any one of claims 1 to 166 wherein the transition metal comprises cobalt and the transition metal catalyst is characterized such that the catalyst exhibits at least about 1.0 x 10²⁶ spins/mole cobalt, at least about 1.25 x 10²⁶ spins/mole cobalt, at least about 1.50 x 10²⁶ spins/mole cobalt, at least about 1.75 x 10²⁶ spins/mole cobalt, at least about 2.0 x 10²⁶ spins/mole cobalt, at least about 2.25 x 10²⁶ spins/mole cobalt, or at least about 2.50 x 10²⁶ spins/mole cobalt when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B.

168. The process, mixture or system as set forth in any one of claims 1 to 167 wherein the transition metal comprises cobalt and the transition metal catalyst is characterized such that the catalyst exhibits less than about 1.0 x 10²⁷ spins/mole cobalt, less than about 7.5 x 10²⁶ spins/mole cobalt, or less than about 5.0 x 10²⁶ spins/mole cobalt when the catalyst is analyzed by Electron Paramagnetic Resonance (EPR) Spectroscopy as described in Protocol B.

169. The process, mixture or system as set forth in any one of claims 1 to 168 wherein the noble metal catalyst comprises a noble metal selected from the group consisting of platinum, palladium, ruthenium, rhodium, iridium, silver, osmium, gold and combinations thereof at a surface of the carbon support of the noble metal catalyst.

170. The process, mixture or system as set forth in claim 169 wherein the noble metal comprises platinum.

171. The process, mixture or system as set forth in any one of claims 1 to 170 wherein the noble metal constitutes from about 2% to about 10% by weight of the noble metal catalyst.

172. The process, mixture or system as set forth in any one of claims 1 to 171 wherein the noble metal constitutes from about 2.5% to about 7.5% by weight of the noble metal catalyst.

173. The process, mixture or system as set forth in any one of claims 1 to 172 wherein the noble metal constitutes from about 3.5% to about 5% by weight of the noble metal catalyst.

174. The process, mixture or system as set forth in any one of claims 1 to 173 wherein the noble metal catalyst further comprises at least one surface promoter selected from the group consisting of tin, cadmium, magnesium, manganese, nickel, aluminum, cobalt, bismuth, lead, titanium, antimony, selenium, iron, rhenium, zinc, cerium, zirconium, tellurium, germanium and combinations thereof.

175. The process, mixture or system as set forth in claim 174 wherein the noble metal catalyst comprises at least one surface promoter selected from the group consisting of iron, bismuth, tin, titanium, cobalt and combinations thereof.

176. The process, mixture or system as set forth in claim 174 or 175 wherein the at least one surface promoter constitutes from about 0.05% to about 5% by weight of the noble metal catalyst .

177. The process, mixture or system as set forth in any one of claims 174 to 176 wherein the at least one surface promoter constitutes from about 0.1% to about 2% by weight of the noble metal catalyst.

178. The process, mixture or system as set forth in claim 177 wherein the at least one surface promoter constitutes from about 0.1% to about 1% by weight of the noble metal catalyst.

179. The process, mixture or system as set forth in any one of claims 1 to 178 wherein the noble metal catalyst comprises iron at a surface of the carbon support.

180. The process, mixture or system as set forth in any one of claims 1 to 179 wherein the noble metal catalyst comprises cobalt at a surface of the carbon support.

181. The process, mixture or system as set forth in any one of claims 1 to 180 wherein the noble metal catalyst comprises iron and cobalt at a surface of the carbon support.

182. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute at least about 0.05% by weight of the noble metal catalyst.

183. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute at least about 0.1% by weight of the noble metal catalyst.

184. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute at least about 0.25% by weight of the noble metal catalyst.

185. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute from about 0.05% to about 2% by weight of the noble metal catalyst.

186. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute from about 0.05% to about 1% by weight of the noble metal catalyst.

187. The process, mixture or system as set forth in claim 181 wherein iron and/or cobalt constitute from about 0.05% to about 0.5% by weight of the noble metal catalyst.

188. The process, mixture or system as set forth in claim 181 wherein iron constitutes from about 0.05% to about 0.25% by weight of the noble metal catalyst and cobalt constitutes from about 0.1% to about 0.6% by weight of the noble metal catalyst.

189. The process, mixture or system as set forth in claim 181 wherein the weight ratio of iron to cobalt is from about 0.1:1 to about 1.5:1.

190. The process, mixture or system as set forth claim 181 wherein the weight ratio of iron to cobalt is from about 0.1:1 to about 1:1.

191. The process, mixture or system as set forth in claim 181 wherein the weight ratio of iron to cobalt is from about 0.15:1 to about 0.5:1.

192. The process, mixture or system as set forth in any one of claims 1 to 191 wherein the noble metal catalyst comprises metal particles at a surface of the carbon support.

193. The process, mixture or system as set forth in claim 192 wherein the noble metal particles comprise noble metal atoms alloyed with at least one promoter in the form of an alloy selected from the group consisting of an intermetallic compound, a substitutional alloy, a multiphasic alloy, an interstitial alloy, and combinations thereof.

194. The process, mixture or system as set forth in any one of claims 1 to 193 wherein the carbon support of the noble metal catalyst has a BET surface area of from about 500 m²/g to about 2100 m²/g.

195. The process, mixture or system as set forth in claim 194 wherein the carbon support of the noble metal catalyst has a BET surface area of from about 500 m²/g to about 1500 m²/g.

196. The process, mixture or system as set forth in claim 194 wherein the carbon support of the noble metal catalyst has a BET surface area of from about 1000 m²/g to about 1500 m²/g.

197. The process, mixture or system as set forth in any one of claims 1 to 196 wherein the noble metal catalyst is characterized as chemisorbing less than about 50 μmoles of carbon monoxide per gram of catalyst during Cycle 2 of static carbon monoxide chemisorption analysis.

198. The process, mixture or system as set forth in any one of claims 1 to 197 wherein the noble metal catalyst is characterized as yielding less than 1.2 mmole of carbon monoxide per gram of catalyst when a dry sample of the noble metal catalyst, after being heated at a temperature of about 500⁰C for about 1 hour in a hydrogen atmosphere and before being exposed to an oxidant following the heating in the hydrogen atmosphere, is heated in a helium atmosphere from about 20° to about 900⁰C at a rate of about 10⁰C per minute, and then at about 900⁰C for about 30 minutes.

199. The process, mixture or system of claim 198 wherein said carbon monoxide yield is no greater than about 0.7 mmole of carbon monoxide per gram of noble metal catalyst.

200. The process, mixture or system of claim 198 wherein said carbon monoxide yield is no greater than about 0.5 mmole of carbon monoxide per gram of noble metal catalyst.

201. The process, mixture or system of claim 198 wherein said carbon monoxide yield is no greater than about 0.3 mmole of carbon monoxide per gram of noble metal catalyst.

202. The process, mixture or system as set forth in any one of claims 1 to 201 wherein the noble metal catalyst is characterized as having a ratio of carbon atoms to oxygen atoms of at least about 20:1 at the surface as measured by x-ray photoelectron spectroscopy after the noble metal catalyst is heated at a temperature of about 500⁰C for about 1 hour in a hydrogen atmosphere and before the noble metal catalyst is exposed to an oxidant following the heating in the hydrogen atmosphere .

203. The process, mixture or system of claim 202 wherein said ratio of carbon atoms to oxygen atoms is at least about 30:1.

204. The process, mixture or system of claim 202 wherein said ratio of carbon atoms to oxygen atoms is at least about 40:1.

205. The process, mixture or system of claim 202 wherein said ratio of carbon atoms to oxygen atoms is at least about 50:1.

206. The process, mixture or system of claim 202 wherein said ratio of carbon atoms to oxygen atoms is at least about 60:1.

207. A process for the oxidation of an organic substrate, the process comprising: contacting a reaction medium comprising an organic substrate with an oxidizing agent in the presence of bismuth, tellurium, a transition metal catalyst, and a noble metal catalyst, wherein: the transition metal catalyst comprises a transition metal composition on a carbon support, wherein the transition metal composition comprises a transition metal and nitrogen; and the noble metal catalyst comprises a noble metal at a surface of a carbon support.

208. The process as set forth in claim 207 wherein bismuth is introduced into a reaction medium comprising the organic substrate, the transition metal catalyst, and the noble metal catalyst .

209. The process as set forth in claim 208 wherein tellurium is introduced into a reaction medium comprising bismuth, the organic substrate, the transition metal catalyst, and the noble metal catalyst.

210. The process as set forth in claim 209 wherein tellurium is introduced to the reaction medium after completion of introduction of bismuth.

211. The process as set forth in claim 209 wherein bismuth and tellurium are introduced to the reaction medium concurrently .

212. The process as set forth in claim 207 wherein tellurium is introduced into a reaction medium comprising the organic substrate, the transition metal catalyst, and the noble metal catalyst.

213. The process as set forth in claim 212 wherein bismuth is introduced into a reaction medium comprising tellurium, the organic substrate, the transition metal catalyst, and the noble metal catalyst.

214. The process as set forth in claim 213 wherein bismuth is introduced to the reaction medium after completion of introduction of tellurium.

215. The process as set forth in claim 213 wherein tellurium and bismuth are introduced to the reaction medium concurrently .

216. The process as set forth in any one of claims 207 to 215 wherein bismuth is introduced into the reaction medium in the form of an inorganic compound containing bismuth.

217. The process as set forth in any one of claims 207 to 216 wherein tellurium is introduced into the reaction medium in the form of an inorganic compound containing tellurium.