WO2007093359A1

WO2007093359A1 - Process for producing sec-butylbenzene

Info

Publication number: WO2007093359A1
Application number: PCT/EP2007/001207
Authority: WO
Inventors: Jane C. Cheng
Original assignee: Exxonmobil Chemical Patents Inc.; Exxonmobil Chemical Limited
Priority date: 2006-02-14
Filing date: 2007-02-08
Publication date: 2007-08-23

Abstract

A process for producing sec-butylbenzene comprises reacting benzene with a C4 alkylating agent under alkylation conditions and in the presence of a catalyst comprising at least one molecular sieve of the MCM-22 family, to produce an alkylation product comprising sec-butylbenzene. The alkylation conditions are controlled so that said alkylation product contains at least 95 wt% sec-butylbenzene, thereby avoiding the need for a subsequent transalkylation process.

Description

PROCESS FOR PRODUCING SEC-BUTYLBENZENE

FIELD

[0001] The present invention relates to a process for producing sec- butylbenzene and for converting the sec-butylbenzene to phenol and methyl ethyl ketone.

BACKGROUND

[0002] Phenol and methyl ethyl ketone are important products in the chemical industry. For example, phenol is useful in the production of phenolic resins, bisphenol A, e-caprolactam, adipic acid, alkyl phenols, and plasticizers, whereas methyl ethyl ketone can be used as a lacquer, a solvent and for dewaxing of lubricating oils. [0003] The most common route for the production of methyl ethyl ketone is by dehydrogenation of sec-butyl alcohol (SBA), with the alcohol being produced by the acid-catalyzed hydration of butenes. For example, commercial scale SBA manufacture by reaction of butylene with sulfuric acid has been accomplished for many years via gas/liquid extraction. [0004] Currently, the most common route for the production of phenol is the Hock process. This is a three-step process in which the first step involves alkylation of benzene with propylene to produce cumene, followed by oxidation of the cumene to the corresponding hydroperoxide and then cleavage of the hydroperoxide to produce equimolar amounts of phenol and acetone. However, the world demand for phenol is growing more rapidly than that for acetone. In addition, the cost of propylene relative to that for butenes is likely to increase, due to a developing shortage of propylene. Thus, a process that uses butenes instead of propylene as feed and coproduces methyl ethyl ketone rather than acetone may be an attractive alternative route to the production of phenol. [0005] It is known that phenol and methyl ethyl ketone can be co-produced by a variation of the Hock process in which sec-butylbenzene is oxidized to obtain sec-butylbenzene hydroperoxide and the peroxide decomposed to the desired phenol and methyl ethyl ketone. An overview of such a process is described in pages 113-421 and 261-263 of Process Economics Report No. 22B entitled "Phenol", published by the Stanford Research Institute in December 1977. [0006] Sec-butylbenzene can be produced by alkylating benzene with a C₄ alkylating agent, such as an n-butene, over an acid catalyst. The chemistry is very similar to ethylbenzene and cumene production. However, as the carbon number of the alkylating agent increases, the number of product isomers also increases. For example, ethylbenzene has one isomer, propylbenzene has two isomers (cumene and n-propylbenzene), and butylbenzene has four isomers (n-, iso-, sec-, and t-butylbenzene). For sec-butylbenzene production, it is important to minimize n-, iso-, t-butylbenzene, and phenylbutenes by-product formation. These byproducts, especially iso-butylbenzene, have boiling points very close to sec- butylbenzene and hence are difficult to separate from sec-butylbenzene by distillation (see table below).

Butylbenzene Boiling Point, °C t-Butylbenzene 169 i-Butylbenzene 171 s-Butylbenzene 173 n-Butylbenzene 183

[0007] Moreover, isobutylbenzene and tert-butylbenzene are known to be inhibitors to the oxidation of sec-butylbenzene to the corresponding hydroperoxide, a necessary next step for the production of methyl ethyl ketone and phenol. [0008] In addition, where the C₄ alkylating agent is an n-butene, the acid catalyst can also facilitate oligomerization reactions to produce higher (C₈+) olefins. These oligomers are also difficult to remove by distillation and have now been found to be deleterious to the oxidation reaction. Again, therefore, it is important to minimize oligomer production in any commercial process for making sec-butylbenzene. [0009] As with any alkylation process to produce monoalkylated aromatics, such as sec-butylbenzene, the reaction between benzene and a C₄ alkylating agent can produce polyalkylated species, particularly dibutylbenzene. For example, in the production of cumene, even the most monoselective catalyst typically produces 10 to 15 wt% of diisopropylbenzene. Thus, most commercial alkylation processes include the steps of separating the polyalkylated species from the alkylation products and then transalkylating the polyalkylated species with additional benzene to increase the yield of monoalkylated product. However, the separation and conversion of the polyalkylated species require additional hardware, which necessarily adds to the cost of overall alkylation process. [0010] According to the invention, it has now been found that, when benzene is alkylated with a C₄ alkylating agent in the presence of a catalyst comprising a molecular sieve of the MCM-22 family, the alkylation conditions can be controlled such that direct product of the alkylation process contains at least 95 wt% sec-butylbenzene and less than 5 wt% of polybutylbenzenes, thereby allowing transalkylation of the polyalkylated species to be avoided. The alkylation product is also very low in butene oligomers and other butylbenzene isomers, especially iso-butylbenzene. [0011] Whereas molecular sieves of the MCM-22 family are known to be monoselective alkylation catalysts, the degree of the monoselectivity with C₄ alkylating agents is unexpected. Although the reason for this result is not fully understood, it is believed that the alkylation occurs at active sites located in surface pockets of the molecular sieves and that the dimensions of these surface pockets are such that polyalkylation with a C₄ species is sterically hindered.

[0012] US Patent No. 4,459,426 discloses a process for the production of alkylated aromatic hydrocarbons by contacting at least a mole-excess of an aromatic hydrocarbon and a C₂ to C₄ olefin under reaction conditions including the presence of a liquid phase in an alkylation reaction zone with an alkylation catalyst comprising a composite of a steam-stabilized hydrogen Y aluminosilicate zeolite and a mineral oxide binder, said steam-stabilized hydrogen Y aluminosilicate zeolite containing less than 0.7 weight percent OfNa₂O and having a unit cell size from 24.00A to about 24.64A. The alkylation product is separated into an unreacted aromatic hydrocarbon fraction, a mono-alkylaromatic fraction, and a poly-alkylaromatic hydrocarbon fraction and a portion of the unreacted aromatic hydrocarbon fraction and the polyalkylaromatic hydrocarbon fraction is subjected to liquid phase transalkylation in a transalkylation zone in the presence of a transalkylation catalyst comprising the composite used in the alkylation step. The olefin can be added in multiple stages and Example 6 discloses the production of secondary butyl benzene from benzene and either n-butenes or a mixture of butene-1, trans-butene-2 and cis-butene-2. According to column 12, lines 37 to 39 "analysis indicated that 92 percent of sec-butylbenzene is produced utilizing the alkylation and transalkylation reactions herein."

[0013] US Patent No. 4,891,458 discloses a process for the alkylation of an aromatic hydrocarbon which comprises contacting a stoichiometric excess of the aromatic hydrocarbon with a C₂ to C₄ olefin under at least partial liquid phase conditions and in the presence of a catalyst comprising zeolite beta. The alkylation process is carried out with addition of olefin in at least two stages, preferably using two or more catalyst beds or reactors in series, with at least a portion of the olefin being added between the catalyst beds or reactors and with interstage cooling being accomplished by the use of a cooling coil or heat exchanger.

[0014] It is known from, for example, U.S. Patent No. 4,992,606 that MCM- 22 is an effective catalyst for alkylation of aromatic compounds, such as benzene, with alkylating agents, such as olefins, having from 1 to 5 carbon atoms over a wide range of temperatures from about 0°C to about 500°C, preferably from about 50°C and about 250°C. Similar disclosures are contained in U.S. Patent Nos. 5,371,310 and 5,557,024 but where the zeolites are MCM-49 and MCM-56 respectively. No information is provided in these patents as to the selectivity of the zeolites to sec-butylbenzene when used as catalysts in the alkylation of benzene with a C₄ alkylating agent. [0015] In our International Application No. PCT/EP2005/008557, filed August 5, 2005, we have described an integrated process for producing phenol and methyl ethyl ketone, the process comprising (a) contacting a feed comprising benzene and a C₄ alkylating agent under alkylation conditions with a catalyst comprising zeolite beta or an MCM-22 family zeolite to produce an alkylation product comprising sec-butylbenzene; (b) oxidizing the sec-butylbenzene to produce a hydroperoxide; and then (c) cleaving the hydroperoxide to produce phenol and methyl ethyl ketone. SUMMARY

[0016] In one aspect, the present invention resides in a process for producing sec-butylbenzene, the process comprising reacting benzene with a C₄ alkylating agent under alkylation conditions and in the presence of a catalyst comprising at least one molecular sieve of the MCM-22 family, to produce an alkylation product comprising at least 95 wt% sec-butylbenzene.

[0017] Preferably, said alkylation conditions include an overall molar ratio of benzene to C₄ alkylating agent from about 3:1 to about 20:1, preferably about 4:1 to about 9:1, more preferably about 5:1 to about 8:1. [0018] Conveniently, said alkylation conditions also include a temperature of from about 60°C to about 260⁰C, a pressure of 7000 kPa or less, and a feed weight hourly space velocity (WHSV) based on C₄ alkylating agent of from about 0.1 to 5O hX^"1. [0019] In one embodiment, said reacting comprises the steps of (a) contacting benzene with a first portion of a C₄ alkylating agent in a first reaction stage to produce an alkylation effluent comprising sec-butylbenzene and unreacted benzene; and

(b) contacting said unreacted benzene with at least one further portion of a C₄ alkylating agent in at least one further reaction stage. [0020] Conveniently, said reaction stages are conducted in a plurality of reaction zones connected in series and each containing said catalyst, with benzene being introduced into the first reaction zone and said alkylating agent being divided between said reaction zones. [0021] Preferably, said reacting is conducted under at least partial liquid phase conditions.

[0022] Conveniently, the molecular sieve of the MCM-22 family has 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. Examples of molecular sieves of the MCM-22 family include MCM-22, PSH-3, SSZ-25, ERB-I, ITQ-I, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8, and mixtures thereof. Preferably, the molecular sieve of the MCM-22 family is selected from MCM-49, MCM-56 and isotypes thereof. [0023] Conveniently, the C₄ alkylating agent in (a) comprises a linear butene, for example 1 -butene and/or 2-butene. In one embodiment, said linear butene is contained in a mixed C₄ stream which is subjected to at least one of sulfur removal, nitrogen removal, oxygenate removal, butadiene removal and isobutene removal prior to the contacting (a). Conveniently, said mixed C₄ stream is a Raffinate-2 stream.

[0024] In yet a further aspect, the present invention resides in sec- butylbenzene formed as the direct product of an aromatics alkylation process and containing at least 95 wt% of sec-butylbenzene. [0025] In still yet a further aspect, the present invention resides in a process for producing phenol and methyl ethyl ketone, the process comprising:

(a) reacting benzene with a C₄ alkylating agent under alkylation conditions and in the presence of a catalyst comprising at least one molecular sieve of the MCM-22 family, to produce an alkylation product comprising sec- butylbenzene;

(b) without subjecting any polybutylbenzenes in said product to a transalkylation reaction, oxidizing the sec-butylbenzene to produce sec- butylbenzene hydroperoxide; and

(c) cleaving the hydroperoxide from (b) to produce phenol and methyl ethyl ketone.

[0026] Conveniently, the oxidizing (b) is conducted in the presence of a catalyst, such as a catalyst selected from (i) an oxo (hydroxo) bridged tetranuclear metal complex comprising manganese, (ii) an oxo (hydroxo) bridged tetranuclear metal complex having a mixed metal core, one metal of the core being a divalent metal selected from Zn, Cu, Fe, Co, Ni, Mn and mixtures thereof and another metal being a trivalent metal selected from In, Fe, Mn, Ga, Al and mixtures thereof, (iii) an N-hydroxy substituted cyclic imide either alone or in the presence of a free radical initiator, and (iv) N,N',N"-trihydroxyisocyanuric acid either alone or in the presence of a free radical initiator. In one embodiment, the oxidization catalyst is a heterogeneous catalyst. [0027] Conveniently, the oxidizing (b) is conducted at a temperature of about 70°C to about 200°C and a pressure of about 0.5 to about 20 atmospheres (50 to 2000 kPa).

[0028] Conveniently, the cleaving (c) is conducted in the presence of a catalyst. The catalyst can be a homogeneous or heterogeneous catalyst. In one embodiment, the catalyst is a homogeneous catalyst, such as sulfuric acid. [0029] Conveniently, the cleaving (c) is conducted at a temperature of about 40°C to about 12O⁰C, a pressure of about 100 to about 2500 kPa, and a liquid hourly space velocity (LHSV) based on the hydroperoxide of about 0.1 to about 100 hr^~\

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] The present invention is directed to a process for producing sec- butylbenzene by alkylating benzene with a C₄ alkylating agent, such as a linear butene, and then converting the sec-butylbenzene to phenol and methyl ethyl ketone. The conversion involves initially oxidizing the sec-butylbenzene to produce the corresponding hydroperoxide and then cleaving the resulting hydroperoxide to produce the desired phenol and methyl ethyl ketone. [0031] In particular, the invention is based on the discovery that by using an MCM-22 family zeolite as the alkylation catalyst and controlling the alkylation conditions, and in particular the concentration of C₄ alkylating agent, the alkylation is unexpectedly (at least 95 wt%) monoselective and produces so little polybutylbenzenes (less than 5 wt%) that a subsequent transalkylation step can be avoided with little or no loss in sec-butylbenzene yield, hi this way, the overall cost and complexity of the alkylation process can be reduced. Moreover, the alkylation product is very low in impurities that can inhibit the oxidation step and, for example, typically contains less than 1 wt %, preferably less than 0.7 wt%, and most preferably less than 0.5 wt%, of butene oligomers and less than 1 wt %, preferably less than 0.7 wt%, and most preferably less than 0.5 wt%, of iso- butylbenzene.

[0032] It is to be appreciated that the process of the invention, as with any alkylation process, produces an effluent that contains unreacted benzene (typically about 60%) as well as the alkylated species, including sec-butylbenzene and polybutylbenzenes. As used herein, the term "alkylation product" refers to the portion of the effluent that contains the alkylated species but excludes the unreacted benzene. Hence a benzene distillation column, or other separation unit, is needed to convert alkylation effluent to "alkylation product", and an s-BB distillation column, or other separation unit, is need to convert the "alkylation product" to sec-butylbenzene.

Benzene Alkylation [0033] The benzene employed in the alkylation step to produce sec- butylbenzene can be any commercially available benzene feed, but preferably the benzene has a purity level of at least 99 wt%.

[0034] The alkylating agent can be any aliphatic compound capable of reaction with benzene and having 4 carbon atoms. Examples of suitable C₄ alkylating agents include monoolefins, such as linear butenes, particularly butene- 1 and/or butene-2; alcohols (inclusive of monoalcohols, dialcohols, trialcohols, etc.) such as the butanols; dialkyl ethers, such as dibutyl ethers; and alkyl halides such as the butyl chlorides. [0035] The alkylating agent can also be an olefinic C₄ hydrocarbon mixture such as can be obtained by steam cracking of ethane, propane, butane, LPG and light naphthas, catalytic cracking of naphthas and other refinery feedstocks and by conversion of oxygenates, such as methanol, to lower olefins. [0036] For example, the following C₄ hydrocarbon mixtures are generally available in any refinery employing steam cracking to produce olefins; a crude steam cracked butene stream, Raffinate-1 (the product of remaining after solvent extraction or hydrogenation to remove butadiene from the crude steam cracked butene stream) and Raffinate-2 (the product remaining after removal of butadiene and isobutene from the crude steam cracked butene stream). Generally, these streams have compositions within the weight ranges indicated in Table A below. Table A

[0037] Other refinery mixed C₄ streams, such as those obtained by catalytic cracking of naphthas and other refinery feedstocks, typically have the following composition:

Propylene - 0-2 wt%

Propane - 0-2 wt%

Butadiene - 0-5 wt%

Butene-1 - 5-20 wt%

Butene-2 - 10-50 wt%

Isobutene - 5-25 wt%

Iso-butane - 10-45 wt%

N-butane - 5-25 wt%

[0038] C₄ hydrocarbon fractions obtained from the conversion of oxygenates, such as methanol, to lower olefins more typically have the following composition:

Propylene - 0-1 wt%

Propane - 0-0.5 wt%

Butadiene - 0-1 wt%

Butene-1 - 10-40 wt%

Butene-2 - 50-85 wt%

Isobutene - 0-10 wt%

N- + iso-butane- 0-10 wt%

[0039] Any one or any mixture of the above C₄ hydrocarbon mixtures can be used in the process of the invention. In addition to linear butenes and butanes, certain of these mixtures contain components, such as isobutene and butadiene, which can be deleterious to the process of the invention. For example, the normal alkylation products of isobutene with benzene are tert-butylbenzene and iso- butylbenzene which, as previously stated, act as inhibitors to the subsequent oxidation step. Thus, prior to the alkylation step, these mixtures may be subjected to butadiene removal and isobutene removal treatments. For example, isobutene can be removed by selective dimerization or reaction with methanol to produce MTBE, whereas butadiene can be removed by extraction or selective hydrogenation to butene-1. Preferably, the C₄ alkylating agent employed in the process of the invention contains less than 1 wt% iso-butene and less than 0.1 wt% butadiene.

[0040] In addition to other hydrocarbon components, commercial C₄ hydrocarbon mixtures typically contain other impurities which could be detrimental to the alkylation process. For example, refinery C₄ hydrocarbon streams typically contain nitrogen and sulfur impurities, whereas C₄ hydrocarbon streams obtained by oxygenate conversion process typically contain unreacted oxygenates and water. Thus, prior to the alkylation step, these mixtures may also be subjected to one or more of sulfur removal, nitrogen removal and oxygenate removal, in addition to butadiene removal and isobutene removal. Removal of sulfur, nitrogen, oxygenate impurities is conveniently effected by one or a combination of caustic treatment, water washing, distillation, adsorption using molecular sieves and/or membrane separation. Water is also typically removed by adsorption. [0041] Conveniently, the total feed to the alkylation step of the present invention 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. [0042] Although not preferred, it is also possible to employ a mixture of a C₄ alkylating agent, as described above, and C₃ alkylating agent, such as propylene, as the alkylating agent in the alkylation step of the invention so that the alkylation step produces a mixture of cumene and sec-butylbenzene. The resultant mixture can then be processed through oxidation and cleavage, to make a mixture of acetone and MEK, along with phenol, preferably where the molar ratio of acetone to phenol is 0.5:1, to match the demand of bisphenol-A production. [0043] The alkylation catalyst used in the present process is a crystalline molecular sieve of the MCM-22 family. The term "MCM-22 family material" (or

"material of the MCM-22 family" or "molecular sieve of the MCM-22 family" or

"MCM-22 family zeolite"), as used herein, includes one or more of: • molecular sieves made from a common first degree crystalline 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. Such crystal structures are discussed in the "Atlas of Zeolite Framework Types", Fifth edition, 2001, the entire content of which is incorporated as reference);

• molecular sieves made from a common second degree building block, being a 2-dimensional tiling of such MWW framework topology unit cells, forming a monolayer of one unit cell thickness, preferably one c-unit cell thickness; • molecular sieves made from common second degree building blocks, being layers of one or more than one unit cell thickness, wherein the layer of more than one unit cell thickness is made from stacking, packing, or binding at least two monolayers of one unit cell thickness. The stacking of such second degree building blocks can be in a regular fashion, an irregular fashion, a random fashion, or any combination thereof; and

• molecular sieves made by any regular or random 2-dimensional or 3- dimensional combination of unit cells having the MWW framework topology.

[0044] Molecular sieves of the MCM-22 family include those molecular sieves having 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 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.

[0045] Materials of the 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-I (described in European Patent No. 0293032), ITQ-I (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. Molecular sieves of the MCM-22 family are preferred as the alkylation catalyst since they have been found to be highly selective to the production of sec-butylbenzene, as compared with the other butylbenzene isomers. Preferably, the molecular sieve is selected from MCM-22, MCM-49, MCM-56 and isotypes of MCM-22, MCM-49 and MCM-56, such as ITQ-2.

[0046] The alkylation catalyst can include the molecular sieve in unbound or self-bound form or, alternatively, the molecular sieve can be combined in a conventional manner with an oxide binder, such as alumina, such that the final alkylation catalyst contains between 2 and 80 wt% sieve.

[0047] In one embodiment, the catalyst is unbound and has a crush strength superior to that of catalysts formulated with binders. Such a catalyst is conveniently prepared by a vapor phase crystallization process, in particular a vapor phase crystallization process that prevents caustic used in the synthesis mixture from remaining in the zeolite crystals as the crystallization occurs.

[0048] The alkylation process is conducted such that the organic reactants, i.e., the alkylatable aromatic compound and the alkylating agent, are brought into contact with the alkylation catalyst described above under effective alkylation conditions controlled so as to maximize the conversion to sec-butylbenzene and minimize the formation of butene oligomers. In particular, a large stoichiometric excess of benzene is fed to the alkylation reaction and the local concentration of the alkylating agent is reduced preferably by staged addition of the alkylating agent. This is conveniently achieved by providing the alkylation catalyst in a plurality of fixed bed reaction zones connected in series. Most or all of the benzene is then fed to the first reaction zone, whereas the alkylating agent is divided into a plurality of equal or different aliquot portions, each of which is fed to a different reaction zone. Alternatively, the alkylation reaction can be conducted in a catalytic distillation reactor, with the alkylating agent being fed to the reactor continuously or in stages over the course of the reaction. In either case, the total amounts of benzene and alkylating agent fed to reaction should be such that the overall molar ratio of benzene to alkylating agent is from about 3:1 to about 20:1, for example from about 4:1 to about 9:1, preferably from about 5:1 to about 8:1.

[0049] In addition, the alkylation conditions conveniently include a temperature of from about 60°C to about 260°C, for example between about 100⁰C and about 200°C, a pressure of 7000 kPa or less, for example from about 1000 to about 3500 kPa, and a weight hourly space velocity (WHSV) based on C₄ alkylating agent of between about 0.1 and about 50 hr^"1, for example between about 1 and about 10 hr^"1.

[0050] The reactants can be in either the vapor phase or partially or completely in the liquid phase and can be neat, i.e., free from intentional admixture or dilution with other material, or they can be brought into contact with the zeolite catalyst composition with the aid of carrier gases or diluents such as, for example, hydrogen or nitrogen. Preferably, the reactants are at least partially in the liquid phase. [0051] Using the catalyst and alkylation conditions described above, it is found that the alkylation step of the process of the invention is highly monoselective and highly selective to sec-butylbenzene. In particular, even using a mixed butene feed such as Raffinate-2, it is found that the alkylation product generally comprises at least 95 wt%, typically at least 97 wt% or at least 98wt%, sec-butylbenzene, less than 5 wt%, typically less than 3 wt% polybutylbenzenes, less than 1 wt% of isobutylbenzene and tert-butylbenzene and less than 1 wt % of butene oligomers. Since the level of polybutylbenzenes in the alkylation product is so low, the alkylation process of the invention dispenses with the transalkylation step normally required to maximize the production of the desired monoalkylated species. Sec-Butyl Benzene Oxidation

[0052) In order to convert the sec-butylbenzene into phenol and methyl ethyl ketone, the sec-butylbenzene is initially oxidized to the corresponding hydroperoxide. This is accomplished by introducing an oxygen-containing gas, such as air, into a liquid phase containing the sec-butylbenzene. Unlike cumene, atmospheric air oxidation of sec-butylbezene in the absence of a catalyst is very difficult to achieve. For example, at 110°C and at atmospheric pressure, sec- butylbenzene is not oxidized, while cumene oxidizes very well under the same conditions. At higher temperature, the rate of atmospheric air oxidation of sec- butylbenzene improves; however, higher temperatures also produce significant levels of undesired by-products.

[0053] Improvements in the reaction rate and selectivity can be achieved by performing sec-butylbenzene oxidation in the presence of a catalyst. Suitable sec- butylbenzene catalysts include a water-soluble chelate compound in which multidentate ligands are coordinated to at least one metal from cobalt, nickel, manganese, copper, and iron. (See U.S. Patent No. 4,013,725). More preferably, a heterogeneous catalyst is used. Suitable heterogeneous catalysts are described in U.S. Patent No. 5,183,945, wherein the catalyst is an oxo (hydroxo) bridged tetranuclear manganese complex and in U.S. Patent No. 5,922,920, wherein the catalyst comprises an oxo (hydroxo) bridged tetranuclear metal complex having a mixed metal core, one metal of the core being a divalent metal selected from Zn, Cu, Fe, Co, Ni, Mn and mixtures thereof and another metal being a trivalent metal selected from In, Fe, Mn, Ga, Al and mixtures thereof. The entire disclosures of said U.S. patents are incorporated herein by reference. [0054] Other suitable catalysts for the sec-butylbenzene oxidation step are the N-hydroxy substituted cyclic imides described in U.S. Patent No. 6,720,462 and incorporated herein by reference, such as N-hydroxyphthalimide, 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-norbomene-2,3-dicarboximide, exo-N-hydroxy-7- oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximide, N-hydroxy-cis-cyclohexane-1,2- dicarboximide, N-hydroxy-cis-4-cyclohexene-l,2 dicarboximide, N- hydroxynaphthalimide sodium salt or N-hydroxy-o-benzenedisulphonimide. Preferably, the catalyst is N-hydroxyphthalimide. Another suitable catalyst is N,N',N"-thihydroxyisocyanuric acid.

[0055] These materials can be used either alone or in the presence of a free radical initiator and can be used as liquid-phase, homogeneous catalysts or can be supported on a solid carrier to provide a heterogeneous catalyst.

[0056] Suitable conditions for the sec-butylbenzene 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 0.5 to about 20 atmospheres (50 to 2000 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, which can help dissolve basic compounds, such as sodium carbonate. The per-pass conversion in the oxidation step is preferably kept below 50%, to minimize the formation of byproducts. The oxidation reaction is conveniently conducted in a catalytic distillation unit and the sec-butylbenzene hydroperoxide produced may be concentrated by distilling off the unreacted sec-butylbenzene prior to the cleavage step.

Hydroperoxide Cleavage

[0057] The final step in the conversion of the sec-butylbenzene into phenol and methyl ethyl ketone involves cleavage of the sec-butylbenzene hydroperoxide, which is conveniently effected by contacting the hydroperoxide with a catalyst in the liquid phase at a temperature of about 20°C to about 150°C, such as about

40°C to about 120⁰C, a pressure of about 50 to about 2500 kPa, such as about 100 to about 1000 kPa and a liquid hourly space velocity (LHSV) based on the hydroperoxide of about 0.1 to about 100 hr^"1, preferably about 1 to about 50 hr^"1.

The sec-butylbenzene hydroperoxide is preferably diluted in an organic solvent inert to the cleavage reaction, such as methyl ethyl ketone, phenol or sec- butylbenzene, to assist in heat removal. The cleavage reaction is conveniently conducted in a catalytic distillation unit.

[0058] The catalyst employed in the cleavage step can be a homogeneous catalyst or a heterogeneous catalyst. [0059] Suitable homogeneous cleavage catalysts include sulfuric acid, perchloric acid, phosphoric acid, hydrochloric acid and p-toluenesulfonic acid.

Ferric chloride, boron trifluoride, sulfur dioxide and sulfur trioxide are also effective homogeneous cleavage catalysts. The preferred homogeneous cleavage catalyst is sulfuric acid [0060] A suitable heterogeneous catalyst for use in the cleavage of sec- butylbenzene hydroperoxide includes a smectite clay, such as an acidic montmorillonite silica-alumina clay, as described in U.S. Patent No. 4,870,217, the entire disclosure of which is incorporated herein by reference.

[0061] The following Examples are given for illustrative purposes and do not limit the scope of the invention.

Example 1 (Comparative)

Sec-butylbenzene synthesis with jet-milled MCM-49 in fixed-bed reactor at

3:1 benzene/2-butene molar ratio [0062] A sample of fresh MCM-49 was jet milled and then extruded with Versal 200 alumina into a 1/16 inch (1.6 mm) quadrulobe catalyst with a nominal composition of 60% zeolite and 40% alumina. 0.4 g of the catalyst was diluted with sand to 3 cc and loaded into an isothermal, down-flow, fixed-bed, tubular reactor having an outside diameter of 9.5 mm (3/8"). The catalyst was dried at 150°C and 1 atm with 100 cc/min flowing nitrogen for 2 hours. The nitrogen was turned off and benzene was fed to the reactor at 60 cc/hr until reactor pressure reached the desired 300 psig (2170 kPa). Benzene flow was then reduced to 7.63 cc/hr. 2-Butene feed (57.1% cis-butene, 37.8% trans-butene, 2.5% n-butane, 0.8% isobutene and 1-butene, and 1.8% others) was introduced from a syringe pump at 2.57 cc/hr. Feed benzene/butene molar ratio was maintained at 3:1 for the entire run. The reactor temperature was adjusted to 160°C. Liquid products were collected at reactor conditions of 160°C and 300 psig (2170 kPa) in a cold-trap and analyzed off line. Butene conversion was determined by measuring unreacted butene relative to feed butene. Representative data are shown in Table 1.

Example 2 Sec-butylbenzene synthesis with jet-milled MCM-49 in Ωxed-bed reactor at 6:1 benzene/2-butene molar ratio

[0063] The process of Example 1 was repeated but using 0.6 g of the jet- milled MCM-49 catalyst and with the feed benzene/butene molar ratio being maintained at 6:1 for the entire run (benzene at 11.47 cc/hr and butene at 1.93 cc/hour). Representative data are also shown in Table 1.

Table 1.

Example Example 1 Example 2

Feed Bz/C4= Weight Ratio 3:1 6:1

Feed BzICA= Molar Ratio 4.2:1 8.4:1

Days on Stream 1.8 2.8 6.8 7.8

Butene WHSV, h^"1 4.0 4.0 2.0 2.0

Benzene WHSV, h^'1 16.7 16.7 16.7 16.7

Butene Conversion, % 96.30 95.41 97.41 97.33

Product Selectivity, wt % i-Butane + n-Butane 0.003 0.003 0.000 0.000

C₅-C₇ 0.055 0.059 0.099 0.107

C₈= 0.443 0.865 0.466 0.474

Cg- 11 0.019 0.042 0.016 0.033

Ci2= + C10-C11 Aromatics 0.157 0.135 0.066 0.073

C13-15 0.158 0.166 0.062 0.071

Cumene 0.243 0.251 0.156 0.159 t-Butylbenzene 0.093 0.078 0.078 0.068 i-Butylbenzene ^* 0.000 0.000 0.000 0.000 s-Butylbenzene 92.547 93.054 96.257 96.244 n-Butylbenzene 0.013 0.009 0.011 0.010

Di-butylbenzene 5.546 5.040 2.667 2.620

Th-butylbenzene 0.405 0.287 0.113 0.125

Heavies 0.320 0.013 0.010 0.016

Sum 100.000 100.000 100.000 100.000 s-Butvlbenzene (BB) Puritv. % t-BB/all BB, % 0.100 0.084 0.081 0.071 i-BB^*/all BB, % 0.000 0.000 0.000 0.000 s-BB/all BB, % 99.886 99.907 99.909 99.919 n-BB/all BB, % 0.014 0.009 0.011 0.011

Di-BBs/BB Wt Ratio, % 6.0 5.4 2.8 2.7

All samples collected at 160⁰C and 300 psig. * iso-Butylbenzene less than 0.5% in total butylbenzene is not detectable with our GC. [0064] When operated at 3:1 benzene/2 -butene molar ratio (or 4.2:1 weight ratio), the 2-butene concentration is 18.9 wt% (1/5.3) if 2-butene mixes with benzene instantaneously. At this benzene/2 -butene molar ratio, the MCM-49 catalyst produced sec-butylbenzene with 93% selectivity. [0065] When operated at 6:1 benzene/2 -butene molar ratio (or 8.4:1 weight ratio), the 2-butene concentration is 10.6 wt% (1/9.4) if 2-butene mixes with benzene instantaneously. At this benzene/2-butene molar ratio, the MCM-49 catalyst produced sec-butylbenzene with 96% selectivity. By-products such as butene oligomers and di-butylbenzenes and tri-butylbenzenes were reduced by about 50%. Thus reducing local concentration of butene in the fixed-bed reactor has a positive impact on sec-butylbenzene selectivity.

[0066] 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 sec-butylbenzene, the process comprising reacting benzene with a C₄ alkylating agent under alkylation conditions and in the presence of a catalyst comprising at least one molecular sieve of the MCM-22 family to produce an alkylation product comprising at least 95 wt% sec-butylbenzene.

2. The process of claim 1, wherein said alkylation conditions include an overall molar ratio of benzene to C₄ alkylating agent from 3:1 to 20:1.

3. The process of claim 2 wherein the molar ratio is from 4: 1 to 9: 1.

4. The process of claim 3 wherein the molar ratio is from 5:1 to 8:1.

5. The process of any preceding claim wherein said alkylation conditions also include a temperature of from 60°C to 260°C and/or a pressure of 7000 kPa or less and/or a feed weight hourly space velocity (WHSV) based on C₄ alkylating agent of from 0.1 to 5O hT ¹.

6. The process of any preceding claim, wherein said reacting comprises the steps of:

(a) contacting benzene with a first portion of a C₄ alkylating agent in a first reaction stage to produce an alkylation effluent comprising sec-butylbenzene and unreacted benzene; and (b) contacting said unreacted benzene with at least one further portion of a C₄ alkylating agent in at least one further reaction stage.

7. The process of claim 6, wherein said reaction stages are conducted in a plurality of reaction zones connected in series and each containing said catalyst, with benzene being introduced into the first reaction zone and said alkylating agent being divided between said reaction zones.

8. The process of any preceding claim, wherein the molecular sieve is selected from MCM-22, PSH-3, SSZ-25, ERB-I, ITQ-I, ITQ-2, MCM-36, MCM- 49, MCM-56, UZM-8, and mixtures of any two or more thereof.

9. The process of any preceding claim, wherein said C₄ alkylating agent comprises a linear butene.

10. The process of claim 9, wherein said linear butene is contained in a mixed C₄ stream.

11. The process of claim 10, wherein said mixed C₄ stream contains less than 1 wt% of iso-butene.

12. The process of any preceding claim, wherein said reacting is conducted under at least partial liquid phase conditions.

13. The direct product of an aromatics alkylation process and comprising at least 95 wt% sec-butylbenzene.

14. The product of claim 13 and comprising at least 96 wt% sec-butylbenzene.

15. The product of claim 13 or 14 and comprising less than 1 wt% of butene oligomers.

16. The product of any one of claims 13 to 15 and comprising less than 0.5 wt% of isobutylbenzene and tert-butylbenzene.

17. A process for producing phenol and methyl ethyl ketone, the process comprising: (a) reacting benzene with a C₄ alkylating agent under alkylation conditions and in the presence of a catalyst comprising at least one molecular sieve of the MCM-22 family to produce an alkylation product comprising sec- butylbenzene;

18. The process of claim 17 wherein said reacting stage (a) comprises a process according to any one of claims 1 to 12.

19. The process of claim 17 or 18, wherein said oxidizing (b) is conducted in the presence of a catalyst.

20. The process of claim 19, wherein said oxidation catalyst is selected from:

(a) an oxo (hydroxo) bridged tetranuclear metal complex comprising manganese;

(b) an oxo (hydroxo) bridged tetranuclear metal complex having a mixed metal core, one metal of the core being a divalent metal selected from Zn, Cu, Fe, Co, Ni, Mn and mixtures thereof and another metal being a trivalent metal selected from In, Fe, Mn, Ga, Al and mixtures thereof; and

(c) an N-hydroxy substituted cyclic imide either alone or in the presence of a free radical initiator.

21. The process of any one of claims 17 to 20, wherein the oxidizing (b) is conducted at a temperature of 70°C to 200°C and/or a pressure of 50 to 2000 kPa (0.5 to 20 atmospheres).

22. The use of a direct product from a benzene alkylation process in a method for producing phenol and methyl ethyl ketone, wherein said direct product comprises at least 95 wt% sec-butylbenzene.

23. The use according to claim 22 wherein said direct product comprises at least 96 wt% sec-butylbenzene.

24. The use according to claim 22 or 23, wherein said direct product comprises less than 1 wt% butene oligomers.

25. The use according to any of claims 22 to 24, wherein said direct product comprises less than 0.5 wt% of isobutylbenzene and tert-butylbenzene.