WO2008101617A1

WO2008101617A1 - Oxidation of sec-butylbenzene and producton of phenol and methyl ethyl ketone

Info

Publication number: WO2008101617A1
Application number: PCT/EP2008/001044
Authority: WO
Inventors: Jihad M. Dakka; Stephen Zushma; Jon E. Stanat
Original assignee: ExxonMobil Chemical Ltd; ExxonMobil Chemical Patents Inc
Current assignee: ExxonMobil Chemical Ltd; ExxonMobil Chemical Patents Inc
Priority date: 2007-02-22
Filing date: 2008-02-07
Publication date: 2008-08-28
Anticipated expiration: 2009-08-22
Also published as: TW200846312A

Abstract

In a process for oxidizing sec-butylbenzene to the corresponding hydroperoxide, a feed containing sec-butylbenzene is contacted with an oxygen- containing gas in a reactor comprising a gas inlet and a gas outlet for said oxygen- containing gas. The contacting is conducted at a temperature, T, in degrees Centigrade, between about 90°C and about 140°C and an oxygen partial pressure at the gas outlet of the reactor, Opp, in kPa determined by the formula (I) (1527.33 - 10.83T) > Opp > (1320.48 - 10.83T) (I), provided that Opp is always greater than zero. The resulting hydroperoxide can be cleaved, optionally in the presence of a catalyst, to co-produce phenol and methyl ethyl ketone.

Description

OXIDATION OF SEC-BUTYLBENZENE AND PRODUCTION OF PHENOL AND METHYL ETHYL KETONE

FIELD

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

BACKGROUND

[0002] 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, alkyl phenols, and plasticizers.

[0003] 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 of butenes is likely to increase, due to a developing shortage of propylene.

[0004] Thus, a process that uses butenes instead of propylene as feed and coproduces methyl ethyl ketone (MEK), rather than acetone may be an attractive alternative route to the production of phenol. For example, there is a growing market for MEK, which is useful as a solvent for lacquers and paints and in dewaxing of lubricating oils.

[0005] It is known that phenol and MEK can be produced from sec- butylbenzene, in a process where 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 1 13-121 and 261-263 of Process Economics Report No. 22B entitled "Phenol", published by the Stanford Research Institute in December 1977. [0006] However, despite the similarities between sec-butyl benzene (SBB) and cumene, the oxidation of sec-butyl benzene to its corresponding hydroperoxide is significantly more difficult to achieve than the oxidation of cumene to cumene hydroperoxide. For example, after 6 hours of oxidizing with air at 1 atm and 1 10°C in the absence of a catalyst, it is possible to achieve greater than 20% conversion of cumene, while at the same conditions one typically achieves less than 1 % conversion of SBB. In the absence of a catalyst, oxidation rates for SBB to its corresponding hydroperoxide only start to become commercially viable at temperatures in excess of 125°C, preferably in excess of 140°C. However, the selectivity towards the hydroperoxide decreases markedly with increasing temperature.

(0007] It is known that the use of certain catalysts, such as n- hydroxyphthalimide (NHPI), enables the oxidation of SBB to occur at temperatures significantly lower than those required in the absence of a catalyst, thereby increasing the selectivity and hence the yield of the desired hydroperoxide. According to the present invention, it has now been found that conversion of SBB goes up with increasing temperature and NHPI concentration, but surprisingly goes through a maximum with respect to total pressure. In contrast, selectivity to sec-butyl benzene hydroperoxide (SBBHP) drops with increasing temperature, is relatively flat with increasing NHPI concentration, and decreases slowly with increasing total pressure. As a result it is found that the SBBHP yield increases with temperature and NHPI concentration, but surprisingly goes through a maximum with total pressure. This maximum is at a different pressure at different temperatures and in particular the optimal pressure decreases with increasing temperature. This response to pressure is surprising in that prior researchers find no pressure effect in the oxidation of cumene at commercial operating temperatures (see, for example, Manfred Weber, Chem. Eng. Technol., 25, (2002) 5, pp 553-558), and cumene is different from SBB by only one methyl group on the alkyl side chain.

|0008] U.S. Patent No. 5,298,667 (Sumitomo) and EP-A-548,986 (Sumitomo) disclose a process for producing phenol and MEK which comprises the steps of (I) oxidizing a material selected from (A) sec-butylbenzene substantially free from ethyl hydroperoxide, carboxylic acids and phenol, (B) sec-butylbenzene substantially free from styrenes, and (C) sec-butylbenzene substantially free from methylbenzyl alcohol, to obtain sec-butylbenzene hydroperoxide, with an oxygen- containing gas, and (II) decomposing the sec-butylbenzene hydroperoxide to obtain phenol and MEK with an acidic catalyst. The oxidation step is conducted in the absence of a catalyst at a temperature of 90°C to 150°C and a pressure of 1 to 10 kg/cm² g (101.3 to 1013 kPag).

[0009) EP-A-1 , 088, 809 (Phenolchemie) discloses a process for producing phenol, MEK and acetone by the oxidation of a mixture containing cumene and up to 25 wt% sec-butylbenzene and the subsequent Hock cleavage of the hydroperoxides, so that the ratio of the phenol:acetone:MEK in the product can be controlled via the composition of the feed mixture. The feed mixture is produced directly by the alkylation of benzene with a corresponding mixture of propene and 1 -butene/2-butene in the presence of a commercial alkylation catalyst such as AlCl₃, H₃PO₄ZSiO₂ or a zeolite. Oxidation takes place in the presence of air or oxygen and in the absence of a catalyst at a temperature of 100⁰C to 140⁰C and a pressure of 1 to 20 bar (100 to 2,000 kPa).

[0010] FR-A-2, 182,802 (Union Carbide) discloses a process for producing phenol and MEK by oxidation of sec-butylbenzene, in which sec-butylbenzene is oxidized to sec-butylbenzene hydroperoxide in the presence of air and optionally in the presence of sec-butylbenzene hydroperoxide, followed by peroxide decomposition. According to this document, the sec-butylbenzene must not contain more than 1 wt% isobutylbenzene, since the presence of isobutylbenzene significantly reduces the overall process efficiency and hence the yield of phenol and MEK. The oxidation step can be conducted at a temperature of 75⁰C to 140⁰C and a pressure of 1 to 10 bar (100 to 10,000 kPa). In the Examples the oxidation is effected at a temperature between 105 and 135°C and an oxygen partial pressure between 20 and 101 kPa.

[0011] U.S. Patent Application Publications Nos. 2004/0162448 (Shell) and 2004/0236152 (Shell) disclose processes for producing phenol and acetone and/or MEK, in which a mixture of cumene and sec-butylbenzene is oxidized to the corresponding peroxides in the presence of oxygen, followed by peroxide decomposition. According to these documents, the addition of a neutralizing base in the oxidation mixture improves the yield in hydroperoxide and reduces the formation of undesired side products. The oxidation step is conducted at a temperature of 90°C to about 15O⁰C and a pressure of 0 psig to about 100 psig (0 to 690 kPag), preferably from about 15 psig to about 40 psig (103 to 276 kPag). In the Examples the oxidation is conducted at a temperature of about 130°C and a pressure of 377 kPa.

[0012] U.S. Patent Nos. 6,852,893 (Creavis) and 6,720,462 (Creavis) describe methods for producing phenol by catalytic oxidation of alkyl aromatic hydrocarbons to the corresponding hydroperoxide, and subsequent cleavage of the hydroperoxide to give phenol and a ketone. Catalytic oxidation takes place with oxygen, in the presence of a free radical initiator and a catalyst, typically an N- hydroxycarbodiimide catalyst, such as N-hydroxyphthalimide, at a temperature of 0 to 500°C, preferably 50 to 300°C, particularly preferably at a temperature of 50 to 200°C, under a pressure of 1 to 100 bar (100 to 1000 kPa). Preferred substrates that may be oxidized by this process include cumene, cyclohexylbenzene, cyclododecylbenzene and sec-butylbenzene.

|0013] U.S. Patent No. 4,136,123 (Goodyear) discloses a process for oxidizing alkylaromatic compounds to the corresponding hydroperoxides in the presence of a sulfonated metallo phthalocyanine catalyst and a free radical initiator selected from the group consisting of alkyl hydroperoxides having from 4 to 6 carbon atoms and aralkyl hydroperoxides having from 8 to 14 carbon atoms. The process is conducted at a temperature of from 50°C to 150⁰C, more preferably from 80°C to 140⁰C, and most preferably from 90⁰C to 12O⁰C and an oxygen pressure of from 2 to 400 psig (13.8 to 2758 kPag), preferably from 50 to 200 psig (345 to 1379 kPag).

[0014| U.S. Patent No. 4,450,303 (Phillips Petroleum) describes a process for making secondary alkyl substituted benzene hydroperoxides by heating a secondary alkyl substituted benzene, such as cyclohexylbenzene, cumene, sec- butylbenzene, sec-pentylbenzene, p-methyl-sec-butylbenzene, 1 ,4- diphenylcyclohexane, para-dicyclohexylbenzene, and sec-hexylbenzene, at a temperature of about 60⁰C to 200°C, preferably about 8O⁰C to 150⁰C, and a pressure from about atmospheric to 1000 psig (0 to 6895 kPag), preferably 50 to about 300 psig (345 to 2069 kPag) in the presence of oxygen. The heating is also conducted in the presence of from about 0.05 to 5 wt% of a samarium catalyst of the formula R¹¹COOSm wherein R" is a Cl to C20 alkyl, aryl, alkaryl, or aralkyl radical and optionally a free radical initiator selected from the group consisting of azo-type compounds and peroxide compounds. In one embodiment, the secondary alkyl substituted benzene is cyclohexylbenzene, the catalyst is samarium acetate and the free radical initiator is cumene hydroperoxide. [0015] In our International Patent Publication No. WO06/015826, we have described a process for producing phenol and methyl ethyl ketone, in which benzene is contacted with a C₄ alkylating agent under alkylation conditions with catalyst comprising zeolite beta or a molecular sieve 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 to produce an alkylation effluent comprising sec- butylbenzene. The sec-butylbenzene is then oxidized to produce a hydroperoxide and the hydroperoxide is decomposed to produce phenol and methyl ethyl ketone. The oxidation step can be conducted with or without a catalyst under conditions including a temperature between about 70⁰C and about 200⁰C, such as about 90⁰C to about 130°C, and a pressure of about 0.5 to about 10 atmospheres (50.6 to 1013 kPa). Exemplified is a process for oxidizing sec-butylbenzene at a temperature of 100⁰C and atmospheric pressure in the presence of a BaMnO₄ catalyst.

SUMMARY

[0016] Accordingly, the invention resides in one aspect in a process for oxidizing sec-butylbenzene to the corresponding hydroperoxide, the process comprising contacting a feed containing sec-butylbenzene with an oxygen- containing gas in a reactor comprising a gas inlet and a gas outlet for said oxygen- containing gas, said contacting being conducted at a temperature, T in degrees Centigrade, between about 90⁰C and about 140⁰C and an oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa determined by the formula (I): (1527.33 - 10.83T) > O_pp > (1320.48 - 10.83T) (I), provided that O_pp is always greater than zero. [0017] In a further aspect, the invention resides in a process for producing phenol and methyl ethyl ketone, the process (which may be referred to herein as the MEKP embodiment) comprising:

(a) contacting benzene and a linear butene under alkylation conditions with catalyst comprising zeolite beta or a molecular sieve of the MCM-22 family to produce an alkylation effluent comprising sec-butylbenzene;

(b) oxidizing the sec-butylbenzene from (a) with an oxygen-containing gas in a reactor comprising a gas inlet and a gas outlet for said oxygen-containing gas, said oxidizing being conducted at a temperature, T in degrees Centigrade, between about 90°C and about 14O⁰C and an oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa determined by the formula (I):

(1527.33 - 10.83T) > O_pp > (1320.48 - 10.83T) (I), provided that O_pp is always greater than zero, the oxidizing converting at least part of the sec-butylbenzene to a corresponding hydroperoxide; and

(c) converting the hydroperoxide from (b) into phenol and methyl ethyl ketone.

[0018] Conveniently, the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa, is determined by the formula (II):

(1492.85 - 1O.83T) > O_pp > (1354.96 - 10.83T) (II), provided that O_pp is always greater than zero. Typically, the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa, is determined by the formula(III):

(1458.38 - 10.83T) > O_pp > (1389.43 - 10.83T) (III), provided that O_pp is always greater than zero.

[0019] The formulae (I), (II) and (III) above were derived by collecting data from designed experiments where the data points were obtained at different temperatures, pressures and catalyst concentrations. The SBB conversion, hydroperoxide selectivity and yield data from these experiments were then subjected to regression analysis followed by application of calculus, in order to define operating conditions for the oxidation process, in terms of oxidation reaction temperature and oxygen partial pressure, that are effective and even optimum for performance of the process of the invention. This regression analysis and application of calculus is described in more detail hereinafter, with reference to the Example and the drawings.

[0020] Conveniently, the oxidizing contact temperature, T, is between about

90°C and about 135°C, for example between about 1 10°C and about 130⁰C, such as between about 1 15°C and about 125°C. The oxygen partial pressure at the gas outlet of the reactor, O_pp, is conveniently between about 21 , 25, 28 or 30 kPa and about 345 kPa, such as between about 35 kPa and about 241 kPa.

[0021] Conveniently, oxidizing the sec-butylbenzene is conducted in the presence of a catalyst, such as an N-hydroxy substituted cyclic imide, typically N- hydroxyphthalimide.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a three-dimensional plot of a temperature, pressure and N- hydroxyphthalimide (NHPI) concentration illustrating the design of the sec- butylbenzene oxidation experiment of the Example.

[0023] Figure 2 is a graph showing the predicted response of the sec- butylbenzene hydroperoxide yield to temperature and NHPI concentration at an oxygen partial pressure of 172 kPa (25 psi) based on regression analysis of the data generated in the Example.

[0024] Figure 3 is a graph showing the predicted response of the sec- butylbenzene hydroperoxide yield to temperature and oxygen partial pressure at an NHPI concentration of 0.05 wt% based on regression analysis of the data generated in the Example.

[0025] Figure 4 is a graph showing the predicted response of the sec- butylbenzene hydroperoxide yield to temperature and oxygen partial pressure at an NHPI concentration of 0.10 wt% based on regression analysis of the data generated in the Example.

[0026] Figure 5 is a graph of the predicted sec-butylbenzene hydroperoxide yield against oxygen partial pressure at 1 15°C and an NHPI concentration of 0.10 wt% based on regression analysis of the data generated in the Example. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention provides a process for oxidizing sec- butylbenzene to the corresponding hydroperoxide and, in one embodiment, then cleaving the hydroperoxide to coproduce phenol and methyl ethyl ketone. In particular, it has been found that, when sec-butyl benzene is oxidized with an oxygen-containing gas, the yield of sec-butyl benzene hydroperoxide can be maximized by operating within a relatively narrow temperature window of between about 90°C and about 140°C, for example between about 100°C and about 135°C, such as between about 1 10°C and about 130°C, conveniently between about 1 15°C and about 125⁰C, and controlling the feed of oxygen- containing gas to the oxidation reactor such that the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa, is determined by the formula (I):

(1527.33 - 10.83T) > O_pp > (1320.48 - 1O.83T) (I), where T is the temperature in the oxidation reactor in degrees Centigrade and provided that O_pp is always greater than zero.

10028) In one embodiment, the feed of oxygen-containing gas is controlled such that the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa, is determined by the formula (II):

(1492.85 - 10.83T) > O_pp > (1354.96 - 10.83T) . (II), provided that O_pp is always greater than zero.

[0029] In another embodiment, the feed of oxygen-containing gas is controlled such that the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa, is determined by the formula (III):

[0030] The sec-butylbenzene used in the present oxidation process and in the MEKP embodiment preferably has a purity of at least 95 wt%, such as at least 97 wt%, for example at least 99 wt% sec-butylbenzene and typically contains less than 1.0 wt%, such as less than 0.5 wt% of butene oligomers and less than 0.5 wt% of isobutylbenzene and tert-butylbenzene.

[0031] Conveniently, the sec-butylbenzene used as feed in the process of the invention and in accordance with the MEKP embodiment is produced by alkylating benzene with at least C₄ alkylating agent under alkylation conditions and preferably in the presence of a heterogeneous catalyst, such as zeolite beta or more preferably at least one molecular sieve of the MCM-22 family (as defined below). The alkylation conditions conveniently include a temperature of from about 60°C to about 260°C, for example between about 100⁰C and about 200⁰C and/or a pressure of 7000 kPa or less, for example from about 1000 to about 3500 kPa and/or 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 hf¹.

[0032] The C₄ alkylating agent conveniently comprises at least one linear butene, namely butene-1, butene-2 or a mixture thereof. The alkylating agent can also be an olefinic C₄ hydrocarbon mixture containing linear butenes, 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. For example, the following C₄ hydrocarbon mixtures are generally available in any refinery employing steam cracking to produce olefins and are suitable for use as the C₄ alkylating agent: a crude steam cracked butene stream, Raffinate-1 (the product 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). [0033] 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 by 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.

[0034] 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 incident radiation and a diffractometer equipped with a scintillation counter and associated computer as the collection system. [0035] 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 (a) MCM- 49, (b) MCM-56 and (c) isotypes of MCM-49 and MCM-56, such as ITQ-2. (0036] Although alkylation of benzene with C₄ alkylating agent over an MCM-22 family zeolite is highly selective to sec-butylbenzene, the effluent from the alkylation reaction will normally contain butene oligomers, which tend to inhibit the subsequent oxidation of the sec-butylbenzene to the corresponding hydroperoxide. Moreover, although distillation is effective to remove some of these impurities, certain butene oligomers, particularly the Ci₂ olefins, tend to boil at or near the same temperature as sec-butylbenzene and hence cannot be readily removed by distillation. Thus, in one embodiment, the present oxidation process employs an initial treatment step, particularly a chemical treatment step, to reduce the level of butene oligomers in the alkylation effluent, typically to less than 1 wt %, preferably less than 0.7 wt%, and most preferably less than 0.5 wt%. |0037] One suitable chemical treatment to reduce the oligomer level in the alkylation effluent involves contacting the effluent with an acid, such as a mineral acid or a solid acid with optional water, at a temperature of for example about 0 to about 300°C to convert the oligomers to alcohols or esters (e.g. esters of sulfuric acid). After neutralization of the excess acid and, if necessary washing, drying, and distillation, the effluent can be fed to the oxidation step. [0038] Another suitable chemical treatment to reduce the oligomer level in the alkylation effluent involves contacting the effluent with hydrogen in the presence of a catalyst, such as a noble metal heterogeneous catalyst, under conditions effective to saturate the oligomers. Suitable conditions include a temperature of about 0 to about 200°C and/or a pressure of about 100 to about 1000 kPa and/or a hydrogen to hydrocarbon mole ratio of about 0.001 to about 10. [0039] A further suitable chemical treatment to reduce the oligomer level in the alkylation effluent involves etherification, in which the effluent is contacted with an alcohol, such as methanol, for example at a temperature of about 20 to about 300°C.

[0040] A combination of the above treatment processes, such as combination of acid treatment and hydrogenation, can be used to reduce the level of butene oligomers in the alkylation effluent to the desired level.

[0041] The oxidizing of sec-butylbenzene to the corresponding hydroperoxide is accomplished by introducing an oxygen-containing gas, such as air, into a reactor having a gas inlet and a gas outlet for the oxygen-containing gas and containing the sec-butylbenzene, typically in the liquid phase. Ideally the sec- butylbenzene is completely or substantially free of cumene. Unlike cumene, atmospheric air oxidation of sec-butylbenzene in the absence of a catalyst is very difficult to achieve. For example, at 1 10°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.

[0042 J 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 organometallic complexes, for example 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, such as a metal oxide catalyst, is used. Suitable heterogeneous metal oxide 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.

[0043] In one embodiment, the catalyst used for the sec-butylbenzene oxidation step is an N-hydroxy substituted cyclic imide as described in U.S. Patent No. 6,720,462 and incorporated herein by reference. Suitable cyclic imides include, for example 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, N₅N¹- 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[2.2.1 ]hept-5-ene-2,3-dicarboximide, N-hydroxy-cis-cyclohexane- 1 ,2-dicarboximide, N-hydroxy-cis-4-cyclohexene- 1 ,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. [0044| 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. [0045] Suitable conditions for sec-butylbenzene oxidation include a temperature between about 90°C and about 140°C, for example between about 90⁰C and about 135°C, such as between about 100°C and about 135⁰C, for example between about 1 10°C and about 130°C, conveniently between about 1 15°C and about 125°C. The oxygen partial pressure at the gas outlet of the reactor is preferably between about 21 , 25, 28 or 30 kPa and about 345 kPa, for example between about 35 and about 241 kPa, such as between about 62 and about 214 kPa. In particular, it is found that by operating within these relatively narrow temperature and pressure windows and by controlling the temperature and oxygen partial pressure such that they obey one or more of the formulae (I) to (III) listed above, the yield sec-butyl benzene hydroperoxide can be maximized in the oxidation process.

[0046] 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 of secondary butyl benzene in the oxidation process 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 (c) in the MEKP embodiment).

[0047J Cleavage of the sec-butylbenzene hydroperoxide produced in the present oxidation process is conveniently effected by contacting the hydroperoxide with a catalyst in the liquid phase at a temperature of about 20⁰C to about 150⁰C, such as about 40⁰C to about 120⁰C, and/or a pressure of about 50 to about 2500 kPa, such as about 100 to about 1000 kPa and/or 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 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.

[0048] The catalyst employed in the cleavage step can be a homogeneous catalyst or a heterogeneous catalyst.

[0049] 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

[0050] 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 (Texaco), the entire disclosure of which is incorporated herein by reference. [0051 J The invention will now be more particularly described with reference to the following non-limiting Example and the accompanying drawings.

Example

[0052] Sec-butylbenzene (150 g) and N-hydroxyphthalimide (ranging from 0.075g to 0.64 g) were weighed into a 300 ml Parr reactor fitted with a stirrer, thermocouple, gas inlet, sampling port and a condenser containing a Dean & Stark type adapter for water removal. The reactor content was stirred at 700 rpm and sparged with nitrogen at a flow rate of 250 cc/minute for 5 minutes. The reactor was pressurized with nitrogen to the desired operating pressure and, while maintaining the nitrogen sparge, the reactor was heated to the desired operating temperature. When the operating temperature was reached, the gas supply was switched from nitrogen to air and the reactor was sparged with air at the desired flow rate for six hours. Samples were taken hourly and, after six hours, the gas supply was switched back to nitrogen and the heat was turned off. When the reactor had cooled, it was depressurized and the contents removed. [0053] A total of 20 data points were taken at different temperatures, pressures and NHPI concentrations in the form of a designed experiment, the design of which is illustrated in Figure 1. The sec-butylbenzene conversion and the sec- butyl benzene hydroperoxide (SBBHP) selectivity and yield data from these runs were then subjected to regression analysis. The data range of the data set employed in the analysis was a temperature range of 1 15° C to 125° C; catalyst (NHPI) concentration in the range 0.05 to 0.43 wt.%; and total pressure in the range 207 to 1379 kPag (30 to 200 psig). The resulting oxygen partial pressures (absolute) were in the range 0 to 276 kPa (0 to 40 psi).

10054] The result of this regression analysis was a regression equation expressing the SBB yield as a function of several independent process variables as shown in Equation 1 :

Equation 1 :

SBB Yield = -130.29 + 1.16O x T(⁰C) + 88.375 x NHPI(wt%) - 104.253 x NHPI(wt%)² + 4.215 x O₂ Partial Pressure(psi) - 0.0102 x O₂ Partial

Pressure(psi) ² - 0.03206 x O₂ Partial Pressure(psi) x T(⁰C)

[0055] Equation 1 defines the SBB yield as a function of Temperature (⁰C), NHPI concentration (wt%), and oxygen partial pressure (psi) for the experimental data set. The SBB yield response as described in Equation 1 is shown graphically in Figures 2 to 4. From these graphs it will be seen that the hydroperoxide yield (%) increases with temperature and NHPI concentration (Figure 2) and goes through a maximum with respect to oxygen partial pressure (Figures 3 to 5). The location of this maximum varies only slightly with NHPI concentration and more significantly with temperature such that at 1 15°C the maximum is at about 172 kPa (25 psi) oxygen partial pressure, at 120°C the maximum is at about 138 kPa (20 psi) oxygen partial pressure and at 125⁰C the maximum is at about 90 kPa (13 psi) oxygen partial pressure. [0056] A mathematical equation defining the location of these maximum SBB yields as a function of oxygen partial pressure and temperature can be determined by applying calculus. The first partial derivative of SBB yield with respect to oxygen partial pressure is determined by calculus, and is shown in Equation 2:

Equation 2:

5(SBB Yieldya O₂ partial pressure = 4.215 - 0.0102 x 2 x O₂ partial pressure (psi) - 0.03206 x T(⁰C)

From calculus it is known that this partial derivative is equal to zero at the optimum, so by setting Equation 2 equal to zero, and solving for oxygen partial pressure there results Equation 3a which describes the optimal oxygen partial pressure (in psi) as a function of temperature (in ⁰C) .

Equation 3a (in psi):

Optimum O₂ Partial Pressure(in psi) = 206.52 - 1.5708 x T(⁰C)

Converting Equation 3a to SI units (kPa) by multiplying by 6.894 kPa per psi, there results Equation 3b which defines the SBB yield optimum with respect to oxygen partial pressure in kPa.

Equation 3b (in kPa):

Optimum O₂ Partial Pressure (kPa) = 1423.91 - 10.83 x T (⁰C)

[0057] The above Equations 3a and 3b provide the optimum O₂ partial pressure for performance of the oxidation process of the invention. On the basis of further data obtained, and applying relatively simple calculation, it has been possible to derive several ranges for the O₂ partial pressure which substantially centre on the optimum but which provide the process operator with degrees of freedom in O₂ partial pressure that nevertheless define effective and preferred operating conditions for performance of the process according to the invention. These ranges, being fit to the data developed during the procedure of defining the invention, are the ranges reflected in Formulae (I), (II) and (III) set out hereinbefore. In particular, the ranges in Formulae (I), (II) and (III) were derived by adding and deducting increments of 15 psi, 10 psi, and 5 psi respectively from the constant in Equation 3 a; or (to within the reasonable bounds of the rounding of unit conversion of psi to kPa) 103.42 kPa, 68.95 kPa, and 34.47 kPa respectively from the constant in Equation 3b. The increments selected were derived by fitting the observed data to the required, preferred and more preferred performance parameters of the inventive process. At some temperatures at or above 125° C subtraction of these increments can yield a negative number for the optimum partial pressure. In these cases, Equation 3 should be considered not to apply at or above that temperature.

[0058] In particularly preferred embodiments, the process of the invention is performed, ideally on sec-butylbenzene that is completely or substantially free of cumene, under a temperature of 90 to 140° C and at an O_pp falling within formula (I), more preferably formula (II) or formula (III). The optimum range for O_pp depends on temperature, and at the higher temperatures the lower limit of the ranges becomes negative. In such cases the lower O_pp value is always greater than zero. In particular, depending on temperature, the O_pp is preferably in the range 21 kPa to 345 kPa, such as 25 kPa to 345 kPa, 28 kPa to 345 kPa or 30 kPa to 345 kPa while always being within the specified formula I, II or III. [0059] 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 oxidizing sec-butylbenzene to the corresponding hydroperoxide, the process comprising contacting a feed containing sec- butylbenzene with an oxygen-containing gas in a reactor comprising a gas inlet and a gas outlet for said oxygen-containing gas, said oxidizing contact being conducted at a temperature, T in degrees Centigrade, between 9O⁰C and 140°C and an oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa determined by the formula (I):

(1527.33 - 10.83T) > O_pp > (1320.48 - 10.83T) (I), provided that O_pp is always greater than zero.

2. A process for producing phenol and methyl ethyl ketone, the process comprising:

(a) contacting benzene and a linear butene under alkylation conditions with a catalyst comprising zeolite beta or a molecular sieve of the MCM-22 family to produce an alkylation effluent comprising sec-butylbenzene;

(b) oxidizing the sec-butylbenzene from (a) by the process according to claim 1 ; and

(c) converting the hydroperoxide from (b) into phenol and methyl ethyl ketone.

3. The process of claim 1 or 2 wherein the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa is determined by the formula (II):

(1492.85 - 10.83T) > O_pp > (1354.96 - 10.83T) (II), provided that O_pp is always greater than zero.

4. The process of claim 3 wherein the oxygen partial pressure at the gas outlet of the reactor, O_pp, in kPa is determined by the formula (III):

5. The process of any one of the preceding claims wherein the oxidizing contact temperature is between 90°C and 135°C.

6. The process of claim 5 wherein the temperature is between 1 10°C and 130°C.

7. The process of claim 6 wherein the temperature is between 1 15°C and 125°C.

8. The process of any one of the preceding claims wherein the oxygen partial pressure at the gas outlet of the reactor is between 21 kPa and 345 kPa.

9. The process of claim 8 wherein the oxygen partial pressure is between 35 kPa and 241 kPa.

10. The process of any one of the preceding claims wherein the oxidizing contact is conducted in the presence of a catalyst.

1 1. The process of claim 10 wherein the catalyst comprises a heterogeneous catalyst.

12. The process of claim 1 1 wherein the heterogeneous catalyst comprises a metal oxide catalyst.

13. The process of claim 10 wherein the catalyst comprises a homogeneous catalyst.

14. The process of claim 13 wherein the homogeneous catalyst comprises an N-hydroxy substituted cyclic imide.

15. The process of claim 14 wherein the homogeneous catalyst comprises N- hydroxyphthalimide.

16. The process of claim 15 wherein the N-hydroxyphthalimide is present in an amount between 0.005 and 20 wt% of the feed.

17. The process of any one of claims 2 to 16 wherein said catalyst in (a) comprises a molecular sieve 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.

18. The process of any one of claims 2 to 17 wherein the linear butene in (a) comprises 1 -butene and/or 2-butene.

19. The process of any one of claims 2 to 18, wherein the converting (c) is conducted in the presence of a catalyst.

20. The process of claim 19, wherein the converting (c) is conducted in the presence of a homogeneous catalyst.

21. The process of claim 20, wherein said homogeneous catalyst comprises at least one of sulfuric acid, perchloric acid, phosphoric acid, hydrochloric acid, p- toluenesulfonic acid, ferric chloride, boron trifluoride, sulfur dioxide and sulfur trioxide.

22. The process of claim 19, wherein the converting (c) is conducted in the presence of a heterogeneous catalyst.

23. The process of claim 22, wherein said heterogeneous catalyst comprises a smectite clay.

24. The process of any one of claims 2 to 23, wherein the converting (c) is conducted at a temperature of 40°C to 120⁰C and/or a pressure of 100 to 1000 kPa and/or a liquid hourly space velocity (LHSV) based on the hydroperoxide of 1 to 50 hr^'1.