WO2012067711A1

WO2012067711A1 - Process for producing phenol

Info

Publication number: WO2012067711A1
Application number: PCT/US2011/052474
Authority: WO
Inventors: Kun Wang; Roberto Garcia
Original assignee: Exxonmobil Chemical Patents Inc.
Priority date: 2010-11-16
Filing date: 2011-09-21
Publication date: 2012-05-24

Abstract

In a process for producing phenol, cyclohexylbenzene is contacted with an oxygen- containing compound in the presence of a first catalyst under oxidation conditions effective to produce an oxidation product comprising cyclohexylbenzene hydroperoxide. At least part of the oxidation product and a polar solvent are then supplied to a cleavage reaction zone, where the said oxidation product and the polar solvent are contacted in the presence of a second catalyst under cleavage conditions including a temperature in excess of 50°C effective to convert at least a portion of the cyclohexylbenzene hydroperoxide into phenol and cyclohexanone.

Description

PROCESS FOR PRODUCING PHENOL PRIORITY CLAIM TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application Serial No. 61/414,042 filed November 16, 2010, the disclosure of which is fully incorporated herein by reference.

FIELD

[0002] The present invention relates to a process for producing phenol.

BACKGROUND

[0003] Phenol is an important product in the chemical industry and is useful in, for example, the production of phenolic resins, bisphenol A, ε-caprolactam, adipic acid, and plasticizers.

[0004] Currently, the most common route for the production of phenol is the Hock process via cumene. This is a three-step process in which the first step involves alkylation of benzene with propylene in the presence of an acidic catalyst to produce cumene. The second step is oxidation, preferably aerobic oxidation, of the cumene to the corresponding cumene hydroperoxide. The third step is the cleavage of the cumene hydroperoxide in the presence of heterogeneous or homogeneous catalysts into equimolar amounts of phenol and acetone, a co- product.

[0005] It is known that phenol and cyclohexanone can be co-produced by a variation of the Hock process in which cyclohexylbenzene is oxidized to obtain cyclohexylbenzene hydroperoxide and the hydroperoxide is decomposed in the presence of an acid catalyst to the desired phenol and cyclohexanone. Although various methods are available for the production of cyclohexylbenzene, a preferred route is disclosed in U.S. Patent No. 6,037,513, which discloses that cyclohexylbenzene can be produced by contacting benzene with hydrogen in the presence of a bifunctional catalyst comprising a molecular sieve of the MCM-22 family and at least one hydrogenation metal selected from palladium, ruthenium, nickel, cobalt and mixtures thereof. The '513 patent also discloses that the resultant cyclohexylbenzene can be oxidized to the corresponding hydroperoxide which is then decomposed to the desired phenol and cyclohexanone co-product.

[0006] In the cumene-based Hock process, dilute cumene hydroperoxide from the cumene oxidation step is first concentrated to greater than 80% by removing unreacted cumene under vacuum, and the resultant concentrate is then sent to the cleavage reactor. In addition to the hazards associated with handling concentrated hydroperoxide, the cleavage poses safety concerns due to the rapid and highly exothermic nature of the reaction. Further, significant amounts of by-products may be generated from the concentrated oxidation products. In practice, therefore, the concentrated cumene hydroperoxide is often diluted with solvents, such as acetone, in order to better manage the heat of reaction and to control by-product formation. For example, U.S. Patent No. 5,254,751 discloses a method of producing phenol and acetone by decomposing cumene hydroperoxide in a non-isothermal manner in the presence of excess acetone whereby the molar ratio of acetone to phenol in a decomposition reactor is from about 1.1 : 1 to 1.5: 1.

[0007] In producing phenol from cyclohexylbenzene, the problems are different. Firstly, oxidation of cyclohexylbenzene to cyclohexylbenzene hydroperoxide is much more difficult than oxidation of cumene and requires elevated temperatures, e.g., 90°C or higher. As a result, the cyclohexylbenzene oxidation effluent is also generally at elevated temperatures so that cooling this stream back to ambient temperature would incur additional operating cost. Also, in view of the high boiling point of cyclohexylbenzene, concentration of the cyclohexylbenzene hydroperoxide by evaporation of the unreacted cyclohexylbenzene is difficult and can lead to unwanted decomposition of the hydroperoxide. Thus, with cyclohexylbenzene hydroperoxide cleavage, the feed contains about 80% hydrocarbon and has very different solubility for the cleavage catalyst, typically sulfuric acid. Consequently, the cleavage products for cyclohexylbenzene hydroperoxide generally contain about 20% polar components which significantly affects the cleavage rate. In addition, the cleavage chemistry for cyclohexylbenzene hydroperoxide is much more complicated than that for cumene hydroperoxide, particularly since more routes for by-product formation exist with cyclohexylbenzene hydroperoxide cleavage. In addition, cyclohexanone is much more prone to acid-catalyzed aldol condensation reactions than acetone so that significant yield loss is possible unless the cyclohexylbenzene hydroperoxide cleavage is closely controlled.

[0008] Research has now shown that cyclohexylbenzene can be converted into phenol and cyclohexanone in high yield by oxidizing the cyclohexylbenzene in the presence of a catalyst, such as N-hydroxyphthalimide (NHPI), and then, optionally without concentrating the oxidation product or removing the NHPI catalyst, cleaving the resultant hydroperoxide in the presence of a polar solvent, such as acetone, at a temperature in excess of 50°C.

[0009] U.S. Patent No. 3,959,381 discloses a method of producing phenol and cyclohexanone by contacting cyclohexylbenzene, preferably in the presence of a member selected from the group consisting of cumene and cumene hydroperoxide, with an oxygen containing gas to form 1 -phenylcyclohexyl hydroperoxide containing intermediate product, optionally purifying said intermediate, contacting the 1 -phenylcyclohexyl hydroperoxide intermediate product with an acid cleavage catalyst in the presence of an alkanone of from 3 to 6 carbons at a temperature of 20°C to 50°C, and recovering the formed phenol and cyclohexanone. The oxidation is conducted in the absence of a catalyst.

[0010] U.S. Patent No. 4,480, 141 discloses a process in which secondary alkyl-substituted hydroperoxides, such as cyclohexylbenzene hydroperoxide, are cleaved to phenols and ketones by contacting the secondary alkyl-substituted benzene hydroperoxide with boron phosphate, at a temperature of about 20°C to 200°C. The cleavage reaction can be carried out in the presence of a solvent, such as acetone and methylethyl ketone.

[0011] U.S. Patent No. 4,487,970 discloses a process in which secondary-alkyl substituted benzene hydroperoxides, such as cyclohexylbenzene hydroperoxide, are cleaved to form phenols and ketones by contacting the secondary-alkyl substituted benzene hydroperoxide with a catalyst consisting essentially of about 3 : 1 to 1 : 10 by weight of SbFs and graphite in the presence of an aromatic or ketone solvent at a temperature of from about 0°C to 100°C. The solvent can be acetone.

[0012] According to the present invention, it has now been found that the cleavage of cyclohexylbenzene hydroperoxide can be facilitated at specific operating conditions by conducting the reaction in the presence of a polar solvent.

SUMMARY

[0013] Accordingly, the invention resides in one aspect in a process for producing phenol, the process comprising:

(a) contacting cyclohexylbenzene with an oxygen-containing compound in the presence of a first catalyst under oxidation conditions effective to produce an oxidation product comprising cyclohexylbenzene hydroperoxide;

(b) supplying at least a portion of said oxidation product and a polar solvent to a cleavage reaction zone; and

(c) contacting said at least a portion of said oxidation product and said polar solvent in the cleavage reaction zone in the presence of a second catalyst under cleavage conditions including a temperature in excess of 50°C effective to convert at least a portion of said cyclohexylbenzene hydroperoxide into phenol and cyclohexanone.

[0014] Conveniently, said first catalyst comprises a cyclic imide, such as N- hydroxyphthalimide. [0015] Conveniently, the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone is in the range of about 1 : 100 to about 100: 1, such as about 1 :20 to about 10: 1. In one embodiment, the polar solvent comprises acetone.

[0016] Conveniently, the second catalyst is an acid catalyst, such as sulfuric acid. In one embodiment, the sulfuric acid is present in an amount between about 0.005 wt% and 0.5 wt% of the total weight of polar solvent and cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone.

[0017] Conveniently, the oxidation product supplied to said cleavage reaction zone comprises about 10 wt% to about 40 wt% of said cyclohexylbenzene hydroperoxide.

[0018] In a further aspect, the invention resides in a process for producing phenol, the process comprising:

(a) hydroalkylating benzene with hydrogen in the presence of a first catalyst under conditions effective to produce a hydroalkylation reaction product comprising cyclohexylbenzene;

(b) separating said cyclohexylbenzene from said hydroalkylation reaction product;

(c) contacting at least a portion of said cyclohexylbenzene with an oxygen- containing compound in the presence of a second catalyst under oxidation conditions effective to produce an oxidation product comprising cyclohexylbenzene hydroperoxide;

(d) supplying at least a portion of said oxidation product and a polar solvent to a cleavage reaction zone; and

(e) contacting said oxidation product and said polar solvent in the cleavage reaction zone in the presence of a third catalyst under cleavage conditions including a temperature in excess of 50°C effective to convert at least a portion of said cyclohexylbenzene hydroperoxide into phenol and cyclohexanone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a graph of cyclohexylbenzene hydroperoxide conversion against time on stream with and without the addition of 5 wt% acetone to the cleavage feed in the cleavage process of Example 3.

[0020] Figure 2 is a graph of phenol yield against time on stream with and without the addition of 5 wt% acetone to the cleavage feed in the cleavage process of Example 3.

[0021] Figure 3 is a graph of cyclohexanone yield against time on stream with and without the addition of 5 wt% acetone to the cleavage feed in the cleavage process of Example 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Described herein is a process for producing phenol from cyclohexylbenzene in which the cyclohexylbenzene is contacted with an oxygen-containing compound in the presence of a first catalyst under oxidation conditions effective to produce an oxidation product comprising cyclohexylbenzene hydroperoxide. Thereafter at least part of the oxidation product and a polar solvent are contacted with a second catalyst under cleavage conditions including a temperature in excess of 50°C effective to convert at least a portion of the cyclohexylbenzene hydroperoxide in the oxidation product into phenol and cyclohexanone.

[0023] Also described is an integrated process for producing phenol from benzene in which the benzene is initially converted to cyclohexylbenzene, conveniently by hydroalkylation, and the cyclohexylbenzene is then subjected to the oxidation and cleavage reactions discussed above. In either event, cyclohexanone can either be recovered from cleavage reaction effluent or can be dehydrogenated to produce additional phenol.

Production of the Cyclohexylbenzene

[0024] The hydroalkylation of benzene to produce cyclohexylbenzene proceeds according to the following reaction (1):

[0025] Any commercially available benzene feed can be used in the hydroalkylation step, but preferably the benzene has a purity level of at least 99 wt%. Similarly, although the source of hydrogen is not critical, it is generally desirable that the hydrogen is at least 99 wt% pure.

[0026] Conveniently, the total feed to the hydroalkylation step contains less than 1000 ppm, such as less than 500 ppm, for example less than 100 ppm, water. In addition, the total feed typically contains less than 100 ppm, such as less than 30 ppm, for example less than 3 ppm, sulfur and less than 10 ppm, such as less than 1 ppm, for example less than 0.1 ppm, nitrogen.

[0027] Hydrogen can be supplied to the hydroalkylation step over a wide range of values, but typically is arranged such that the molar ratio of hydrogen to benzene in the hydroalkylation feed is between about 0.15: 1 and about 15: 1, such as between about 0.4: 1 and about 4: 1 , for example between about 0.4 and about 0.9: 1.

[0028] The hydroalkylation reaction may be effected in the presence of a bifunctional catalyst comprising a molecular sieve and a hydrogenation metal. In one preferred embodiment, the molecular sieve comprises an MCM-22 family material. The term "MCM-22 family material" (or "material of the MCM-22 family" or "molecular sieve of the MCM-22 family"), as used herein, includes molecular sieves made from a building block unit cell, which unit cell has the MWW framework topology. A unit cell is a spatial arrangement of atoms which if tiled in three-dimensional space describes the crystal structure. MWW framework topology is disclosed and described in the "Atlas of Zeolite Framework Types", Fifth Edition, 2001, the entire content of which is incorporated as reference.

[0029] Molecular sieves of MCM-22 family generally have an X-ray diffraction pattern including d-spacing maxima at 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Angstrom. The X-ray diffraction data used to characterize the material (b) are obtained by standard techniques using the K-alpha doublet of copper as the incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. Molecular sieves of MCM-22 family include MCM-22 (described in U.S. Patent No. 4,954,325); PSH-3 (described in U.S. Patent No. 4,439,409); SSZ-25 (described in U.S. Patent No. 4,826,667); ERB-1 (described in European Patent No. 0293032); ITQ-1 (described in U.S. Patent No 6,077,498); ITQ-2 (described in International Patent Publication No. WO97/17290); MCM-36 (described in U.S. Patent No. 5,250,277); MCM-49 (described in U.S. Patent No. 5,236,575); MCM-56 (described in U.S. Patent No. 5,362,697); UZM-8 (described in U.S. Patent No. 6,756,030); and mixtures thereof. Preferably, the molecular sieve is selected from (a) MCM- 49; (b) MCM-56; and (c) isotypes of MCM-49 and MCM-56, such as ITQ-2.

[0030] Any known hydrogenation metal can be employed in the hydroalkylation catalyst, although suitable metals include palladium, ruthenium, nickel, zinc, tin, and cobalt, with palladium being particularly advantageous. Generally, the amount of hydrogenation metal present in the catalyst is between about 0.05 wt% and about 10 wt%, such as between about 0.1 wt% and about 5 wt%, of the catalyst. In one embodiment, where the MCM-22 family molecular sieve is an aluminosilicate, the amount of hydrogenation metal present is such that the molar ratio of the aluminum in the molecular sieve to the hydrogenation metal is from about 1.5 to about 1500, for example from about 75 to about 750, such as from about 100 to about 300. [0031] The inorganic oxide employed in such a composite hydroalkylation catalyst is not narrowly defined provided it is stable and inert under the conditions of the hydroalkylation reaction. Suitable inorganic oxides include oxides of Groups 2, 4, 13, and 14 of the Periodic Table of Elements, such as alumina, titania, and/or zirconia. As used herein, the numbering scheme for the Periodic Table Groups is as disclosed in Chemical and Engineering News, 63(5), 27 (1985).

[0032] Suitable binder materials include synthetic or naturally occurring substances as well as inorganic materials such as clay, silica and/or metal oxides. The latter may be either naturally occurring or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be used as a binder include those of the montmorillonite and kaolin families, which families include the subbentonites and the kaolins commonly known as Dixie, McNamee, Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be used in the raw state as originally mined or initially subjected to calcination, acid treatment or chemical modification. Suitable metal oxide binders include silica, alumina, zirconia, titania, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-beryllia, silica-titania as well as ternary compositions such as silica-alumina-thoria, silica-alumina-zirconia, silica- alumina-magnesia and silica-magnesia-zirconia.

[0033] Although the hydroalkylation reaction using an MCM-22 family zeolite catalyst described herein is highly selective towards cyclohexylbenzene, the effluent from the hydroalkylation reaction may contain some dicyclohexylbenzene by-product. Depending on the amount of this dicyclohexylbenzene, it may be desirable to either (a) transalkylate the dicyclohexylbenzene with additional benzene or (b) dealkylate the dicyclohexylbenzene to maximize the production of the desired monoalkylated species.

[0034] Transalkylation with additional benzene is typically effected in a trans alky lation reactor, separate from the hydroalkylation reactor, over a suitable transalkylation catalyst, including large pore molecular sieves such as a molecular sieve of the MCM-22 family, zeolite beta, MCM-68 (see U.S. Patent No. 6,014,018), zeolite Y, zeolite USY, and mordenite. A large pore molecular sieve has an average pore size in excess of 7 A in some embodiments or from 7 A to 12 A in other embodiments. The transalkylation reaction is typically conducted under at least partial liquid phase conditions, which suitably include a temperature of about 100°C to about 300°C, a pressure of about 800 kPa to about 3500 kPa, a weight hourly space velocity of about 1 hr ¹ to about 10 hr ¹ on total feed, and a benzene/dicyclohexylbenzene weight ratio about of 1 : 1 to about 5: 1. The transalkylation reaction effluent can then be returned to the second distillation tower to recover the additional monocyclohexylbenzene product produced in the transalkylation reaction.

[0035] Another significant by-product of the hydroalkylation reaction is cyclohexane. Although a C6-rich stream comprising cyclohexane and unreacted benzene can be readily removed from the hydroalkylation reaction effluent by distillation, owing to the similarity in the boiling points of benzene and cyclohexane, the C6-rich stream is difficult to further separate by simple distillation. However, some or all of the C6-rich stream can be recycled to the hydroalkylation reactor to provide not only part of the benzene feed but also part of the diluents mentioned above.

[0036] In some cases, it may be desirable to supply some of the C6-rich stream to a dehydrogenation reaction zone, where the C6-rich stream is contacted with a dehydrogenation catalyst under dehydrogenation conditions sufficient to convert at least part of the cyclohexane in the C6-rich stream portion to benzene, which again can be recycled to the hydroalkylation reaction. The dehydrogenation catalyst generally comprises (a) a support; (b) a hydrogenation- dehydrogenation component; and (c) an inorganic promoter. Conveniently, the support (a) is selected from the group consisting of silica, a silicate, an aluminosilicate, zirconia, and carbon nanotubes, and preferably comprises silica. Suitable hydrogenation-dehydrogenation components (b) comprise at least one metal selected from Groups 6 to 10 of the Periodic Table of Elements, such as platinum, palladium and compounds and mixtures thereof. Typically, the hydrogenation-dehydrogenation component is present in an amount between about 0.1 and about 10 wt% of the catalyst. A suitable inorganic promoter (c) comprises at least one metal or compound thereof selected from Group 1 of the Periodic Table of Elements, such as a potassium compound. Typically, the promoter is present in an amount between about 0.1 wt% and about 5 wt% of the catalyst. Suitable dehydrogenation conditions include a temperature of about 250°C to about 500°C, a pressure of about atmospheric to about 500 psig (100 kPa to 3550 kPa), a weight hourly space velocity of about 0.2 hr ¹ to 50 hr ¹, and a hydrogen to hydrocarbon feed molar ratio of about 0 to about 20.

[0037] Other disadvantageous impurities of the hydroalkylation reaction are bicyclohexyl (BCH) and the methylcyclopentylbenzene (MCPB) isomers which, because of the similarity in their boiling points, are difficult to separate from the desired cyclohexylbenzene by distillation. Moreover, although 1,2-methylcyclopentylbenzene (2-MCPB), and 1,3- methylcyclopentylbenzene (3 -MCPB) are readily converted in the subsequent oxidation/cleavage steps to the phenol and methylcyclopentanones, which are valuable products, 1, 1-methylcyclopentylbenzene (1-MCPB) is substantially inert to the oxidation step and so, if not removed, will build up in the C₁₂ stream. Similarly, bicyclohexyl (BCH) can lead to separation problems downstream. Thus, at least part of the hydroalkylation reaction product may be treated with a catalyst under conditions to remove at least 1, 1- methylcyclopentylbenzene and/or bicyclohexyl from the product. The catalyst is generally an acid catalyst, such as an aluminosilicate zeolite, and especially faujasite and the treatment may be conducted at a temperature of about 100°C to about 350°C, such as about 130°C to about 250°C, for a time of about 0.1 to about 3 hours, such as about 0.1 to about 1 hours. The catalytic treatment is believed to isomerize the 1, 1-methylcyclopentylbenzene to the more readily oxidizable 1,2-methylcyclopentylbenzene (2-MCPB), and 1,3- methylcyclopentylbenzene (3-MCPB). The bicyclohexyl is believed to react with benzene present in the hydroalkylation reaction product to produce cyclohexane and more of the desired cyclohexylbenzene according to the following reaction:

[0038] The catalytic treatment can be conducted on the direct product of the hydroalkylation reaction or after distillation of the hydroalkylation reaction product to separate the Ce and/or the heavies fraction.

[0039] The cyclohexylbenzene product from the hydroalkylation reaction and any downstream reaction to remove the impurities discussed above is separated from the reaction effluent(s) and is fed to the oxidation reaction described in more detail below.

Cyclohexylbenzene Oxidation

[0040] In order to convert the cyclohexylbenzene into phenol and cyclohexanone, the cyclohexylbenzene is initially oxidized to the corresponding hydroperoxide. This is accomplished by contacting the cyclohexylbenzene with an oxygen-containing compound, such as air and various derivatives of air. For example, it is possible to use air that has been compressed and filtered to removed particulates, air that has been compressed and cooled to condense and remove water, or air that has been enriched in oxygen above the natural approximately 21 mol% in air through membrane enrichment of air, cryogenic separation of air or other conventional means. [0041] The oxidation is conducted in the presence of a catalyst. Suitable oxidation catalysts include N-hydroxy substituted cyclic imides described in U.S. Patent No. 6,720,462, which is incorporated herein by reference for this purpose. For example, N- hydroxyphthalimide (NHPI), 4-amino-N-hydroxyphthalimide, 3-amino-N- hydroxyphthalimide, tetrabromo-N-hydroxyphthalimide, tetrachloro-N-hydroxyphthalimide, N-hydroxyhetimide, N-hydroxyhimimide, N-hydroxytrimellitimide, N-hydroxybenzene- 1,2,4- tricarboximide, N,N'-dihydroxy(pyromellitic diimide), N,N'-dihydroxy(benzophenone- 3,3',4,4'-tetracarboxylic diimide), N-hydroxymaleimide, pyridine-2,3-dicarboximide, N- hydroxysuccinimide, N-hydroxy(tartaric imide), N-hydroxy-5-norbornene-2,3-dicarboximide, exo-N-hydroxy-7-oxabicyclo[2.2. l]hept-5-ene-2,3-dicarboximide, N-hydroxy-cis- cyclohexane-l,2-dicarboximide, N-hydroxy-cis-4-cyclohexene-l,2 dicarboximide, N- hydroxynaphthalimide sodium salt or N-hydroxy-o-benzenedisulphonimide may be used. Preferably, the catalyst is N-hydroxyphthalimide. Another suitable catalyst is Ν,Ν',Ν"- thihydroxyisocyanuric acid.

[0042] These oxidation catalysts can be used either alone or in conjunction with a free radical initiator, and further can be used as liquid-phase, homogeneous catalysts or can be supported on a solid carrier to provide a heterogeneous catalyst. Typically, the N-hydroxy substituted cyclic imide or the Ν,Ν',Ν''-trihydroxyisocyanuric acid is employed in an amount between 0.0001 wt% to 15 wt%, such as between 0.001 wt% to 5 wt%, of the cyclohexylbenzene.

[0043] Suitable conditions for the oxidation step include a temperature between about 70°C and about 200°C, such as about 90°C to about 130°C, and a pressure of about 50 kPa to 10,000 kPa. A basic buffering agent may be added to react with acidic by-products that may form during the oxidation. In addition, an aqueous phase may be introduced. The reaction can take place in a batch or continuous flow fashion.

[0044] The reactor used for the oxidation reaction may be any type of reactor that allows for introduction of oxygen to cyclohexylbenzene, and may further efficaceously provide contacting of oxygen and cyclohexylbenzene to effect the oxidation reaction. For example, the oxidation reactor may comprise a simple, largely open vessel with a distributor inlet for the oxygen-containing stream. In various embodiments, the oxidation reactor may have means to withdraw and pump a portion of its contents through a suitable cooling device and return the cooled portion to the reactor, thereby managing the exothermicity of the oxidation reaction. Alternatively, cooling coils providing indirect cooling, say by cooling water, may be operated within the oxidation reactor to remove the generated heat. In other embodiments, the oxidation reactor may comprise a plurality of reactors in series, each conducting a portion of the oxidation reaction, optionally operating at different conditions selected to enhance the oxidation reaction at the pertinent conversion range of cyclohexylbenzene or oxygen, or both, in each. The oxidation reactor may be operated in a batch, semi-batch, or continuous flow manner.

[0045] Typically, the product of the cyclohexylbenzene oxidation reaction contains at least 5 wt%, such as at least 10 wt%, for example at least 15 wt%, or at least 20 wt% cyclohexyl-1 - phenyl-1 -hydroperoxide based upon the total weight of the oxidation reaction effluent. Generally, the oxidation reaction effluent contains no greater than 80 wt%, or no greater than 60 wt%, or no greater than 40 wt%, or no greater than 30 wt%, or no greater than 25 wt% of cyclohexyl-1 -phenyl- 1 -hydroperoxide based upon the total weight of the oxidation reaction effluent. The oxidation reaction effluent may further comprise imide catalyst and unreacted cyclohexylbenzene. For example, the oxidation reaction effluent may include unreacted cyclohexylbenzene in an amount of at least 50 wt%, or at least 60 wt%, or at least 65 wt%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt%, based upon total weight of the oxidation reaction effluent.

[0046] At least a portion of the oxidation reaction effluent may be subjected to a cleavage reaction, with or without undergoing any prior separation or treatment. For example, all or a fraction of the oxidation reaction effluent may be subjected to high vacuum distillation to generate a product enriched in unreacted cyclohexylbenzene and leave a residue which is concentrated in the desired cyclohexyl-1 -phenyl- 1 -hydroperoxide and which is subjected to the cleavage reaction. In general, however, such concentration of the cyclohexyl-1 -phenyl- 1- hydroperoxide is neither necessary nor preferred. Additionally or alternatively, all or a fraction of the oxidation effluent, or all or a fraction of the vacuum distillation residue may be cooled to cause crystallization of the unreacted imide oxidation catalyst, which can then be separated either by filtration or by scraping from a heat exchanger surface used to effect the crystallization. At least a portion of the resultant oxidation composition reduced or free from imide oxidation catalyst may be subjected to the cleavage reaction.

[0047] As another example, all or a fraction of the oxidation effluent may be subjected to water washing and then passage through an adsorbent, such as a 3A molecular sieve, to separate water and other adsorbable compounds, and provide an oxidation composition with reduced water or imide content that may be subjected to the cleavage reaction. Similarly, all or a fraction of the oxidation effluent may undergo a chemically or physically based adsorption, such as passage over a bed of sodium carbonate to remove the imide oxidation catalyst (e.g., NHPI) or other adsorbable components, and provide an oxidation composition reduced in oxidation catalyst or other adsorbable component content that may be subjected to the cleavage reaction. Another possible separation involves contacting all or a fraction of the oxidation effluent with a liquid containing a base, such as an aqueous solution of an alkali metal carbonate or hydrogen carbonate, to form an aqueous phase comprising a salt of the imide oxidation catalyst, and an organic phase reduced in imide oxidation catalyst. An example of separation by basic material treatment is disclosed in International Application No. WO 2009/025939.

Hydroperoxide Cleavage

[0048] The final reactive step in the conversion of the cyclohexylbenzene into phenol and cyclohexanone involves the catalyzed cleavage of the cyclohexyl-1 -phenyl- 1 -hydroperoxide produced in the oxidation step.

[0049] Generally, the catalyst used in the cleavage reaction is an acid catalyst that is at least partially soluble in the cleavage reaction mixture being supplied to the cleavage reaction zone, is stable at a temperature of at least 185°C and has a lower volatility (higher normal boiling point) than cyclohexylbenzene. Typically, the acid catalyst is also at least partially soluble in the cleavage reaction product that is being produced in the cleavage reaction zone. Suitable acid catalysts include, but are not limited to, Bronsted acids, Lewis acids, sulfonic acids, perchloric acid, phosphoric acid, hydrochloric acid, p-toluene sulfonic acid, aluminum chloride, oleum, sulfur trioxide, ferric chloride, boron trifluoride, sulfur dioxide and sulfur trioxide. Sulfuric acid is a preferred acid catalyst.

[0050] In various embodiments, the cleavage reaction mixture contains at least 50 weight- parts-per-million (wppm) and no greater than 5000 wppm of the acid catalyst, or at least 100 wppm and no greater than 3000 wppm, or at least 150 wppm and no greater than 2000 wppm of the acid catalyst, or at least 300 wppm and no greater than 1500 wppm of the acid catalyst, based upon total weight of the cleavage reaction mixture.

[0051] In one embodiment, the cleavage reaction zone is supplied with a polar solvent, such as an alcohol containing less than 6 carbons, such as methanol, ethanol, iso-propanol, and/or ethylene glycol; a nitrile, such as acetonitrile and/or propionitrile; nitromethane; and a ketone containing 6 carbons or less such as acetone, methylethyl ketone, 2- or 3-pentanone, cyclohexanone, and methylcyclopentanone. The preferred polar solvent that is added to the cleavage reaction zone is acetone. Generally, the polar solvent is added to the cleavage reaction zone such that the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to the cleavage reaction zone is in the range of about 1 : 100 to about 100: 1, such as about 1 :20 to about 10: 1, and the cleavage reaction mixture being supplied to the cleavage reaction zone comprises about 10 wt% to about 40 wt% of the cyclohexylbenzene hydroperoxide. The addition of the polar solvent is found not only to increase the degree of conversion of the cyclohexylbenzene hydroperoxide in the cleavage reaction but also to increase the selectivity of the conversion to phenol and cyclohexanone. Although the mechanism is not fully understood, it is believed that the polar solvent reduces the free radical induced conversion of the cyclohexylbenzene hydroperoxide to undesired products such as hexanophenone and phenylcyclohexanol.

[0052] In various embodiments, the cleavage reaction mixture includes cyclohexylbenzene in an amount of at least 50 wt%, or at least 55 wt%, or at least 60 wt%, or at least 65 wt%, or at least 70 wt%, or at least 80 wt%, or at least 90 wt%, based upon total weight of the cleavage reaction mixture.

[0053] Suitable cleavage conditions include a temperature of greater than 50°C and no greater than 200°C, or at least 55°C and no greater than 200°C, or at least 60°C and no greater than 200°C, or at least 70°C and no greater than 200°C, or at least 80°C and no greater than 200°C, or at least 90°C and no greater than 200°C, or at least 100°C and no greater than 200°C, and a pressure of at least 1 and no greater than 370 psig (at least 7 and no greater than 2,550 kPa, gauge), or at least 14.5 and no greater than 145 psig (at least 100 and no greater than 1 ,000 kPa, gauge) such that the cleavage reaction mixture is completely or predominantly in the liquid phase during the cleavage reaction.

[0054] The reactor used to effect the cleavage reaction may be any type of reactor known to those skilled in the art. For example, the cleavage reactor may be a simple, largely open vessel operating in a near-continuous stirred tank reactor mode, or a simple, open length of pipe operating in a near-plug flow reactor mode. In other embodiments, the cleavage reactor comprises a plurality of reactors in series, each performing a portion of the conversion reaction, optionally operating in different modes and at different conditions selected to enhance the cleavage reaction at the pertinent conversion range. In one embodiment, the cleavage reactor is a catalytic distillation unit.

[0055] In various embodiments, the cleavage reactor is operable to transport a portion of the contents through a cooling device and return the cooled portion to the cleavage reactor, thereby managing the exothermicity of the cleavage reaction. Alternatively, the reactor may be operated adiabatically. In one embodiment, cooling coils operating within the cleavage reactor(s) remove any heat generated. [0056] The major products of the cleavage reaction of cyclohexyl- 1 -phenyl- 1 - hydroperoxide are phenol and cyclohexanone, each of which generally comprise about 40 wt% to about 60 wt%, or about 45 wt% to about 55 wt% of the cleavage reaction product, such wt% based on the weight of the cleavage reaction product exclusive of unreacted cyclohexylbenzene and acid catalyst.

[0057] The cleavage reaction product also typically contains unreacted acid catalyst and hence at least a portion of the cleavage reaction product is normally neutralized with a basic material to remove or reduce the level of acid in the product.

[0058] Suitable basic materials include alkali metal hydroxides and oxides, alkali earth metal hydroxides and oxides, such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, calcium hydroxide, calcium oxide, and barium hydroxide. Sodium and potassium carbonates may also be used, optionally at elevated temperatures.

[0059] In various embodiments, the basic material comprises one or more of: a caustic exchange resin; ammonia or ammonium hydroxide; a basic clay such as limestone, dolomite, magnesite, sepiolite and olivine; an activated carbon and/or impregnated activated carbon; an anionic exchange resin, such as a weakly basic ion exchange resin having a styrene-divinyl benzene polymer backbone and an amine functional structure selected from -N(CH₃)₂, -NRH or -NR₂, where R is a hydrogen or an alkyl group containing 1 to 20 carbon atoms; an amine polysiloxane functionalized with ethylenediamine; an organic basic material grafted on microporous or mesoporous metal oxides; other organo-inorganic solids, such as zeolites exchanged with a metal selected from the group of lithium, sodium potassium, rubidium, cesium, calcium, barium, strontium and radium; an oxide of Group III of the Periodic Table of Elements treated with a metal selected from lithium, potassium, sodium, rubidium and cesium; a supported or solid alkali, alkaline-earth metal or organometallic; a magnesium silicate generally derived from the interaction of a magnesium salt and soluble silicate; a salt with basic hydrolysis such as sodium acetate, sodium bicarbonate, sodium phenate and sodium carbonate; and amine(s), such as a primary, secondary, or tertiary aliphatic amines or aromatic amines, e.g., anilines, n-butyl amine, heterocyclic amines, such as pyridines, piperidines, piperazines, tri-ethyl amine, aliphatic or aromatic diamines and alkanolamines. In particular, amines in the form of their salts with weak organic acids may be used. Conveniently, the basic material is a diamine, such as 2-methylpentamethyenediamine or hexamethylenediamine, which are commercially available from Invista S.a r.l. Corporation under the trade designations DYTEK™ A and DYTEK™ HMD. [0060] Suitable solid basic materials include: basic metal oxide families; alkali on metal oxides; alkaline-earth on metal oxides; alkali and alkaline-earth zeolites; transition metals, rare earth and high valence oxides; hydrotalcites, calcined hydrotalcites and spinels, specifically hydrotalcites treated with an alkali metal selected from lithium, potassium, sodium, rubidium, cesium, and combinations thereof; perovskites; and beta-aluminas.

[0061] In one embodiment, the basic material is one or more of the hindered amines described in U.S. Patent No. 6,201,157. It will be understood that the basic material may be added in the anhydrous state or may be an aqueous solution of any of the foregoing basic materials, particularly the metal hydroxides and salts with basic hydrolysis.

[0062] Conveniently, a liquid basic material employed in a neutralization reaction in the present invention, such as an amine or diamine as has been discussed, has a relatively low volatility, with a normal boiling point temperature above that of cyclohexylbenzene, such that it will tend to remain in the bottoms product in subsequent fractionation operations that may be conducted on the least a portion of the treated cleavage reaction product that may contain such liquid basic material.

[0063] The conditions at which the neutralization reaction is effected vary with the acid catalyst and basic material employed. Suitable neutralization conditions include a temperature of at least 30°C, or at least 40°C, or at least 50°C, or at least 60°C, or at least 70°C, or at least 80°C, or at least 90°C. Other suitable neutralization conditions include a temperature of no greater than 200°C, or no greater than 190°C, or no greater than 180°C, or no greater than 170°C, or no greater than 160°C, or no greater than 150°C, or no greater than 140°C, or no greater than 130°C, or no greater than 120°C, or no greater than 110°C, or no greater than 100°C. In various embodiments, the neutralization conditions include a temperature that is reduced from cleavage reaction conditions, for example, the temperature may be 1°C, or 5°C, or 10°C, or 15°C, or 20°C, or 30°C, or 40°C lower than the temperature of the cleavage reaction.

[0064] Suitable neutralization conditions may include a pressure of about 1 psig to about 500 psig (5 kPa, gauge to 3450 kPa, gauge), or about 10 psig to 200 psig (70 kPa, gauge to 1380 kPa, gauge) such that the treated cleavage reaction mixture is completely or predominantly in the liquid phase during the neutralization reaction.

[0065] After neutralization, the neutralized acid product can be removed from the cleavage product leaving a crude mixture of phenol and cyclohexanone which can be purified and separated by methods well known in the art. Uses of Cvclohexanone and Phenol

[0066] The cyclohexanone produced through the processes disclosed herein may be used, for example, as an industrial solvent, as an activator in oxidation reactions and in the production of adipic acid, cyclohexanone resins, cyclohexanone oxime, caprolactam and nylons, such as nylon 6 and nylon 6,6.

The phenol produced through the processes disclosed herein may be used, for example, to produce phenolic resins, bisphenol A, ε-caprolactam, adipic acid and/or plasticizers.

[0067] The invention will now be more particularly described with reference to the following non-limiting Examples and the accompanying drawings.

Example 1; Oxidation of cyclohexylbenzene

[0068] An amount of 631 g of cyclohexylbenzene (TCI America, Inc.) was added to a 1- liter four-necked glass flask, to which 0.6702 grams of N-hydroxyphthalimide (NHPI) (TCI America, Inc.) was added. The flask was then fitted with a reflux condenser, a mechanical stirrer, a gas sparger, and a thermometer. An air flow of 250 cc/min was bubbled through the liquid via the gas sparger; and the content was heated at 110°C with stirring (560 rpm) for 6 hours. The flask was allowed to cool down to room temperature and the oxidation product recovered. Gas chromatography (GC) analysis indicated the product to contain 17.9% by weight of cyclohexylbenzene hydroperoxide (CHBHP).

Example 2; Removal of NHPI

[0069] An amount of 300 grams of the oxidation products from Example 1 was placed in a 500-mL glass flask and mixed with 30 grams of anhydrous sodium carbonate (granular form, Aldrich). The mixture was stirred overnight and the solid became brick-red in color. The solid was then removed by filtration and the liquid further filtered through a bed of anhydrous magnesium sulfate. A clear, light-yellow liquid was obtained. GC analysis revealed the product to contain 17.5% by weight of CHBHP.

Example 3; Cleavage of CHBHP

[0070] To help determine conversion and selectivity, the product from Example 2 was mixed with anhydrous dodecane (~ 8 wt%, Aldrich) as an internal standard for mass balance. Typically 30 grams of the feed generated in this fashion was placed in a 50-cc jacketed glass reactor with a circulating temperature bath. The bath was set to the desired temperature (55°C) and the reactor content was allowed to equilibrate. Once the temperature stabilized, a GC sample was taken for the hot feed. The desired amount of concentrated sulfuric acid (96%, triple-distilled, Aldrich) was then added via a micro-syringe. After a brief reaction exotherm, as indicated by the temperature rise inside the reactor, 1-cc aliquots were taken at certain time intervals and neutralized with a stoichiometric amount of dihexylamine. The samples generated were analyzed by GC.

[0071] When acetone was used in the cleavage, the same procedures were used except that a desired amount of acetone was mixed with the CHBHP feed containing the internal standard.

[0072] Table 1 and Figures 1 to 3 compare the CHBHP conversion and the yield of phenol and cyclohexanone with and without the use of acetone. Clearly presence of acetone in the cleavage feed improves both conversion and selectivity to desired products.

Table 1

[0073] As used herein, "CHBHP conversion" means the amount of cyclohexylbenzene hydroperoxide converted to any product. "Phenol selectivity" is relative to the theoretical phenol yield based upon the amount of cyclohexylbenzene hydroperoxide converted. "Cyclohexanone selectivity" is relative to the theoretical cyclohexanone yield based upon the amount of cyclohexylbenzene hydroperoxide converted.

[0074] While the present invention has been described and illustrated by reference to particular embodiments, those of ordinary skill in the art will appreciate that the invention lends itself to variations not necessarily illustrated herein. For this reason, then, reference should be made solely to the appended claims for purposes of determining the true scope of the present invention.

Claims

1. A process for producing phenol, the process comprising:

2. The process of claim 1, wherein said first catalyst comprises a cyclic imide.

3. The process of any one of the preceding claims, wherein said first catalyst comprises N-hydroxyphthalimide.

4. The process of any one of the preceding claims, wherein the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone is in the range of about 1 : 100 to about 100: 1.

5. The process of any one of the preceding claims, wherein the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone is in the range of about 1 :20 to about 10: 1.

6. The process of any one of the preceding claims, wherein the polar solvent comprises acetone.

7. The process of any one of the preceding claims, wherein said second catalyst is an acid catalyst.

8. The process of any one of the preceding claims, wherein said second catalyst comprises sulfuric acid.

9. The process of claim 8, wherein said sulfuric acid is present in an amount between about 0.005 wt% and 0.5 wt% of the total weight of polar solvent and cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone.

10. The process of any one of the preceding claims, wherein said oxidation product supplied to said cleavage reaction zone comprises about 10 wt% to about 40 wt% of said cyclohexylbenzene hydroperoxide.

1 1. A process for producing phenol, the process comprising:

(b) separating at least a portion of said cyclohexylbenzene from said hydroalkylation reaction product;

(c) contacting at least a portion of said separated cyclohexylbenzene with an oxygen-containing compound in the presence of a second catalyst under oxidation conditions effective to produce an oxidation product comprising cyclohexylbenzene hydroperoxide;

(e) contacting said at least a portion of said oxidation product and said polar solvent in the cleavage reaction zone in the presence of a third catalyst under cleavage conditions including a temperature in excess of 50°C effective to convert at least a portion of said cyclohexylbenzene hydroperoxide into phenol and cyclohexanone.

12. The process of claim 1 1, wherein said first catalyst comprises a metal-containing zeolite of the MCM-22 family.

13. The process of any one of claims 1 1 to 12, wherein said second catalyst comprises a cyclic amide.

14. The process of any one of claims 1 1 to 13, wherein said second catalyst comprises N- hydroxyphthalimide.

15. The process of any one of claims 1 1 to 14, wherein the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone is in the range of about 1 : 100 to about 100: 1.

16. The process of any one of claims 1 1 to 15, wherein the weight ratio of the polar solvent to the cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone is in the range of about 1 :20 to about 10: 1.

17. The process of any one of claims 11 to 16, wherein the polar solvent comprises acetone.

18. The process of any one of claims 1 1 to 17, wherein said third catalyst is an acid catalyst.

19. The process of any one of claims 1 1 to 18, wherein said third catalyst comprises sulfuric acid.

20. The process of claim 19, wherein said sulfuric acid is present in an amount between about 0.005 and 0.5 weight % of the total weight of polar solvent and cyclohexylbenzene hydroperoxide supplied to said cleavage reaction zone.

21. The process of any one of the preceding claims, wherein said oxidation product supplied to said cleavage reaction zone comprises about 10 to about 40 weight % of said cyclohexylbenzene hydroperoxide.