WO1998006665A1

WO1998006665A1 - Synthesis of m41s materials

Info

Publication number: WO1998006665A1
Application number: PCT/US1997/013952
Authority: WO
Inventors: Wieslaw Jerzy Roth
Original assignee: Mobil Oil Corporation
Priority date: 1996-08-16
Filing date: 1997-08-12
Publication date: 1998-02-19
Also published as: ZA977329B

Abstract

M41S materials are synthesized from an aqueous reaction mixture comprising sources of an oxide of a tetravalent element Y, hydroxyl ions and an organic surfactant R', wherein R' comprises an ion of the formula R1R2R3R4Q+, wherein Q is nitrogen or phosphorus and wherein at least one of R¿1?, R2, R3 and R4 is aryl or alkyl of from 6 to about 36 carbon atoms or combinations thereof, the remainder of R1, R2, R3 and R4 being selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof, and wherein the OH/surfactant molar ratio is in the approximate range 0.9-1.2, more preferably 1.0-1.15. By controlling the surfactant level within the above ranges it is found that high quality M41S materials with excellent adsorption properties can be produced at surfactant utilization levels.

Description

SYNTHESIS OF M4 IS MATERIALS This invention relates to a process for the synthesis of meosporous crystalline M41S materials, e.g., MCM-41.

Porous inorganic solids have great utility as catalysts and separation media for industrial applications. Catalytic and sorptive activity are enhanced by the extensive surface area provided by a readily accessible microstructure characteristic of these solids. Until recently, porous inorganic solids generally belonged to three broad classes: a) amorphous or paracrystalline materials, such as amorphous silica and transitional aluminas, which exhibit little or no long range order as detectable by X-ray diffraction and which have a wide distribution of pore sizes, generally between 10 and 200 Angstrom; b) molecular sieve materials, such as aluminosilicate zeolites, which are highly ordered materials with well-defined and characteristic X-ray diffraction patterns and pores of uniform size, generally less than 20 Angstrom; and c) pillared layered materials, such as disclosed in U.S. Patent No. 4,859,648, which fall generally between classes (a) and (b) both in terms of the regularity of their microstructure and the distribution and size of their pores. U.S. Patent No. 5,102,643 discloses a new class of porous inorganic solid, termed M41 S materials which are crystalline and non-layered but have uniform pores within the mesoporous range of 15-200 Angstrom. In particular, M41 S materials are defined in U. S.

Patent No. 5,102,643 as inorganic, porous, non-layered crystalline phase materials exhibiting, after calcination, an x-ray diffraction pattern with at least one peak at a d- spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsoφtion capacity of greater than 15 grams benzene per 100 grams of said material at 50 torr and 25 °C.

U.S. Patent No. 5,098,684 discloses a particular form of M41S material, defined as MCM-41, which has a hexagonal arrangement of uniform size pores with a diameter of at least 15 Angstrom and a hexagonal electron diffraction pattern which can be indexed with a d value greater than 18 Angstrom. As disclosed in U. S. Patent No. 5, 102,643, synthesis of M41 S materials conventionally involves contacting a quaternary ammonium surfactant, such as a cetyltrimethylammonium compound, with a source of an oxide of a tetravalent element, such as silica, in an aqueous, alkaline environment at a temperature of 25-250°C. The surfactants required are relatively expensive materials and, in conventional syntheses, surfactant utilization has been significantly less than 100%. This not only increases the raw material costs but necessitates expensive post-synthesis techniques to recycle and/or dispose of unused surfactant.

One potential solution to this problem is to employ the low surfactant concentrations suggested in U.S. Patent No. 5,308,602, in which the surfactant/water molar ratio is less than 0.004. However, the products of this synthesis have relatively poor x-ray crystallinity and adsoφtion properties.

In accordance with the present invention, it has now been found that high quality M41 S materials with excellent adsoφtion properties can be produced at surfactant utilization levels approaching 100% if the OH/surfactant molar ratio is maintained in the approximate range of 0.9 to 1.15, more preferably 1.0-1.15. The present invention therefore resides in a process for producing an inorganic, porous, non-layered crystalline phase material exhibiting, after calcination, an x-ray diffraction pattern with at least one peak at a d-spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsoφtion capacity of greater than 15 grams benzene per 100 grams of said material at 50 torr and 25 °C, the process comprising the steps of:

(a) preparing an aqueous reaction mixture capable of forming said material and comprising sources of an oxide of a tetravalent element Y, hydroxyl ions and an organic surfactant R', wherein R' comprises an ion of the formula RιR₂R₃ Q⁺, wherein Q is nitrogen or phosphorus and wherein at least one of R-, R₂, R₃ and R₄ is aryl or alkyl of from 6 to about 36 carbon atoms or combinations thereof, the remainder of Rj, R₂, R₃ and i being selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof, and wherein the OH/surfactant molar ratio is in the approximate range of 0.9 to 1.15; (b) maintaining said mixture under sufficient conditions of temperature and time for the formation of said crystalline phase material; and (c) recovering said said crystalline phase material. Preferably, the OH surfactant molar ratio is in the range 1.0-1.15. Preferably, the reaction mixture comprises an additional organic material R", wherein R" comprises an ion of the formula RsRβRvRgQ , wherein Q is nitrogen or phosphorus and wherein each of R_s, Re, R7 and Rg is selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof and the process includes the additional step, prior to step (a), of reacting the material R" with a solid source of the oxide of the tetravalent element Y.

The present invention provides an improved process for producing the mesoporous crystalline M41S material described in U.S. Patent No. 5,102,643. In its calcined form this material has the following composition:

NMW.XbYeZdOh)

wherein W is a divalent element, such as a divalent first row transition metal, e.g. manganese, cobalt and iron, and/or magnesium, preferably cobalt; X is a trivalent element, such as aluminum, boron, iron and/or gallium, preferably aluminum; Y is a tetravalent element such as silicon and/or germanium, preferably silicon; Z is a pentavalent element, such as phosphorus; M is one or more ions, such as, for example, ammonium, Group IA, IIA and VIIB ions, usually hydrogen, sodium and/or fluoride ions; n is the charge of the composition excluding M expressed as oxides; q is the weighted molar average valence of M; n/q is the number of moles or mole fraction of M; a, b, c, and d are mole fractions of W, X, Y and Z, respectively; h is a number of from 1 to 2.5; and (a+b+c+d) = 1.

A preferred embodiment of the above crystalline material is when (a+b+c) is greater than d, and h = 2. A further embodiment is when a and d = 0, and h = 2.

In its as-synthesized form, the material of this invention has a composition, on an anhydrous basis, expressed empirically as follows:

wherein R is the total organic material not included in M as an ion, and r is the coefficient for R, i.e. the number of moles or mole fraction of R. The M and R components are associated with the material as a result of their presence during crystallization, and are easily removed or, in the case of M, replaced by conventional post-crystallization methods.

The synthesis process of the invention comprises the step of forming an aqueous reaction mixture comprising a source of the tetravalent element oxide YO₂, optionally together with sources of oxides of the elements W, X and Z, a source of hydroxyl ions and an organic surfactant R', wherein R' comprises an ion of the formula RιR₂R₃R Q⁺, wherein Q is nitrogen or phosphorus and wherein at least one of Ri, R₂, R₃ and R_tis aryl or alkyl of from 6 to about 36 carbon atoms or combinations thereof, the remainder of Ri, R₂, R₃ and » being selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof and wherein the OH/surfactant molar ratio is in the range 0.9-1.15, preferably 1.0-1.15. The Y/surfactant molar ratio is preferably less than 8 and is preferably in the range 5-8 when hexagonal MCM-41 is the desired product.

Suitable surfactants R' include cetyltrimethylammonium, cetyltrimethylphosphonium, decyltrimethylammonium, dodecyltrimethylammonium, dimethyldidodecylammonium, octadecyltrimethylphosphonium, cetylpyridinium and myristyltrimethylammonium compounds.

In addition, the reaction mixture preferably includes an additional organic material R", wherein R" comprises an ion of the formula

wherein Q is nitrogen or phosphorus and wherein each of R₅, Re, R₇ and Rg is selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof. Suitable additional organic materials R" include tetramethylammonium, tetraethylammonium and tetrapropylammomum compounds. For example R" can be tetramethylammonium silicate, in which case it also provides some or all of the source of silica. Alternatively and more preferably, R" is tetramethylammonium hydroxide and, prior to addition of the surfactant R', R" is reacted with a solid source of silica, typically at 40-150°C, to produce tetramethylammonium silicate in situ.

Other components of the reaction mixture and the molar ratios of these components are as described in U.S. Patent No. 5, 102,643.

Crystallization to produce M41 S material from the above reaction mixture can be conducted at a temperature of 25-250°C for 1 hour to 14 days, but is more preferably conducted at 25-150°C for 2-24 hours. After crystallization, the M41 S product is separated from the reaction mixture, generally by filtration, and recovered. Using the OH surfactant ratio of the invention, it is found that the filtrate is generally free of surfactant indicating substantially complete surfactant utilization.

The M41S material produced by the process of the invention is useful in a wide variety of soφtion and catalytic applications. Prior to such use, the material is preferably treated, generally by heating to at least 370°C for up to 20 hours, to remove the organic constituents used in the synthesis.

In one preferred application the M41S material of the invention is used as a catalytic cracking catalyst and most preferably a fluid catalytic cracking (FCC) catalyst. In this case the M41 S material is preferably treated with phosphorus and combined with a matrix material, such as a clay, silica, alumina or a mixture thereof. The cracking catalyst may also contain a conventional zeolite cracking component, which would typically have a pore size of 6-9 Angstrom. Suitable zeolite cracking components would include faujasite, ordenite, zeolite X, rare-earth exchanged zeolite X (REX), zeolite Y, zeolite Y (HY), rare earth-exchanged ultra stable zeolite Y (RE-US Y), dealuminized Y (DAY), ultrahydrophobic zeolite Y (UHP-Y), dealuminized silicon enriched zeolites such as LZ- 210, zeolite ZK-5, zeolite ZK-4, zeolite Beta, zeolite Omega, zeolite L and ZSM-20 The invention will now be more particularly described with reference to the following Examples. Example 1

Precipitated silica (UltraSil, 30g), 25wt% teramethylammonium hydroxide (TMA-OH, 30g) and 140 g of water were reacted in a steambox at 95°C for 1 hr. A 29wt% solution of cetyltrimethylammonium chloride (CTMA-C1, 80 g) surfactant was added to give a mixture with the following molar composition:

TMA-OH surfactant 1.14

Silica/surfactant 6.2

TMA-OH/silica 0.18

The mixture was reacted at 150 °C for 24 hours to give a product which exhibited a 4-peak x-ray diffraction pattern of MCM-41 with the d-spacing of the first line at 45

A. After calcination the 4-peak pattern was retained but with the d-spacing of the first line at 42 A. The calcined product exhibited the following properties: approximate pore opening 40 A (from nitrogen isotherm), BET - 1050 m²/g, adsoφtion capacity for water and cyclohexane of 7. lg and >50g, per 100 g of sorbate, respectively. A mass balance calculated on the basis of the composition of the as-synthesized product indicated complete surfactant utilization.

Example 2 A mixture having the same molar composition, and produced by the same method, as in example 1 was reacted at 95 ^CC overnight (about 16 hours). The product exhibited a 4-peak x-ray pattern of MCM-41 with the d-spacing of the first line at 44 A. After calcination the 4-peak pattern was retained but with the d-spacing of the first line at 38 A. The calcined product exhibited the following properties: approximate pore opening 30 A (from nitrogen isotherm), BET - 830 m /g, adsoφtion capacity for water, cyclohexane and n-hexane of 4.9g, 40.3g and 35.6g, per 100 g of sorbate, respectively.

Example 3 Precipitated silica (UltraSil, 30g), 25wt% TMA-OH (30g) and 140 g of water were reacted in a steambox at 95 °C for 1 hr. Al(isopropoxide)₃ (9.2g) was added and the mixture again reacted in the steambox. A 29wt% solution of cetyltrimethylammonium chloride (CTMA-C1, 80 g) surfactant was added to give a mixture with the following molar composition: TMA-OH/surfactant 1.14 Silica/surfactant 6.2

TMA-OH/silica 0.18

Silica/alumina 48

The mixture was reacted at 150°C for 36 hours to give a product which exhibited a 3 -peak x-ray pattern of MCM-41 with the d-spacing of the first line at 40 A. .After calcination the 3-peak pattern was retained but with the d-spacing of the first line at

34 A. The calcined product exhibited the following properties: approximate pore opening 25-30 A (from nitrogen isotherm), BET - 750 m²/g, adsoφtion capacity for water and cyclohexane of 31g and 23g, per 100 g of sorbate, respectively.

Example 4 A mixture having the same molar composition, and produced by the same method, as in example 1 was reacted at 150°C for 6 hours. The product exhibited a 4-peak x-ray pattern of MCM-41 with the d-spacing of the first line at 45 A. (Analysis: Ash 35.8%, C 24.5%, N 1.41%). After calcination the 4-peak pattern was retained but with the d-spacing of the first line at 40 A. The calcined product exhibited the following properties: BET - 1069 m²/g, adsoφtion capacity for water and cyclohexane of lOg and >50g, per 100 g of sorbate, respectively.

Examples 5-13 The process of the preceding Examples was repeated as outlined in Table 1 below produce MCM-41 products with properties summarized in the Table.

TABLE 1

Comparative Example A Example 1 was repeated but with the TMA-OH/surfactant molar ratio reduced to 0.64 and the TMA-OH/silica molar ratio at 0.10. Reaction at 150°C for 24 hours yielded only partial conversion of the silica to M41S material as indicated by the following reduced soφtion properties for the calcined product:

BET 530

Sortion capacity

(per 1 OOg sorbate)

- water ₄g

-cyclohexane 30g.

Comparative E) cample B

The starting materials of Example 1 were used to produce a reaction mixture with the following molar composition:

TMA-OH/surfactant 1.26

Silica surfactant 4.6

TMA-OH/silica 0.27

Reaction at 95 °C for 16 hours produced MCM-41 material but, after filtration to separate the MCM-41 crystals, surfactant was found in the filtrate. In the as-synthesized form, the crystalline product had an x-ray pattern in which the first line had a d-spacing at 42 A. After calcination the d-spacing of the first line had decreased to 34 A suggesting that the product was of limited stability.

Claims

Claims:

1. A process for producing an inorganic, porous, non-layered crystalline phase material exhibiting, after calcination, an x-ray diffraction pattern with at least one peak at a d-spacing greater than about 18 Angstrom Units with a relative intensity of 100 and a benzene adsoφtion capacity of greater than 15 grams benzene per 100 grams of said material at 50 ton^* and 25 °C, the process comprising the steps of:

(a) preparing an aqueous reaction mixture capable of forming said material and comprising sources of an oxide of a tetravalent element Y, hydroxyl ions and an organic surfactant R', wherein R' comprises an ion of the formula RjR₂R₃RιQ⁺, wherein Q is nitrogen or phosphorus and wherein at least one of Ri, R₂, R₃ and R» is aryl or alkyl of from 6 to about 36 carbon atoms or combinations thereof, the remainder of Ri, R₂, R₃ and R- being selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof, and wherein the OH/surfactant molar ratio is in the approximate range of 0.9 to 1.15;

(b) maintaining said mixture under sufficient conditions of temperature and time for the formation of said crystalline phase material; and

(c) recovering said said crystalline phase material.

2. The process of claim 1, wherein the OH surfactant molar ratio is in the approximate range 1.0-1.15.

3. The process of claim 1, wherein the Y/surfactant molar ratio is less than 8.

4. The process of claim 1, wherein the Y/surfactant molar ratio is in the approximate range 5-8.

5. The process of claim 1 wherein the surfactant is selected from the group consisting of cetyltrimethylammonium, cetyltrimethylphosphonium, decyltrimethylammonium, dodecyltrimethylammonium, dimethyldidodecylammonium, octadecyltrimethylphosphonium, cetylpyridinium and myristyltrimethylammonium compounds.

6. The process of claim 1, wherein the reaction mixture comprises an additional organic material R", wherein R" comprises an ion of the formula R₅R6R₇ 8Q⁺, wherein Q is nitrogen or phosphorus and wherein each of R₅, R*, R₇ and R« is selected from the group consisting of hydrogen, alkyl of from 1 to 5 carbon atoms and combinations thereof.

7. The process of claim 6 including the additional organic material R" is a tetramethylammonium, tetraethylammonium, or a tetrapropylammonium compound.

8. The process of claim 1 wherein the conditions in step (b) include a temperature within the approximate range of 25 to 250°C and a time of about 1 hour to about 14 days.

9. The process of claim 1 wherein the conditions in step (b) include a temperature within the approximate range of 25 to 150°C and a time of about 2 to 24 hours.