Zeolite-based ethylabenzene process adaptable to an aluminum chl

Chemistry of hydrocarbon compounds – Plural serial diverse syntheses – To produce aromatic

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585313, 585316, 585450, 585467, 585475, C07C 100, C07C 264, C07C 268, C07C 522

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059591684

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BRIEF SUMMARY
This invention relates to a process of alkylating benzene with ethylene in the presence of a catalytic zeolite to form ethylbenzene.
Ethylbenzene is used to prepare styrene from which polystyrene is prepared.
Historically, ethylbenzene is commercially manufactured by the liquid phase alkylation of benzene with ethylene in the presence of a Friedel-Crafts catalyst, most typically aluminum chloride. Hydrogen chloride may be required as a co-catalyst. (See, for example, K. Weissermel and H.-J. Arpe, Industrial Organic Chemistry, 2.sup.nd ed., VCH Press, Weinheim, Germany, 1993, pp. 333-336.) An aluminum chloride ethylbenzene plant typically comprises a benzene drying stage, a catalyst preparation stage, an alkylation stage, a transalkylation stage, a neutralization and catalyst disposal stage, and an aromatic product recovery (distillation) stage.
As regards the alkylation stage, the selectivity to ethylbenzene is enhanced by using a high benzene/ethylene molar ratio, typically around 3:1. Nevertheless, the product mixture obtained from the alkylation contains benzene, ethylbenzene, and polyethylbenzenes including diethylbenzenes, triethylbenzenes, tetraethylbenzenes, and optionally higher polyethyl-benzenes. The alkylation product mixture is fed to a transalkylation reactor and contacted with a transalkylation catalyst, such as an aluminum chloride complex. A transalkylation product mixture is obtained having a composition close to that expected for thermodynamic equilibrium, which provides the maximum attainable ethylbenzene. The product mixture from the transalkylator, after neutralization, is separated in the aromatics recovery stage of the plant which typically comprises a three column distillation train. The first column recovers benzene which may then be recycled to the alkylation reactor or to the transalkylation reactor. The second column recovers the desired ethylbenzene end-product. The third column recovers diethylbenzenes and triethylbenzenes, and if present, higher polyethylbenzenes.
An aluminum chloride-based ethylbenzene plant has several disadvantages, among them, the corrosiveness of the alkylation catalyst and process streams. Accordingly, high investment and maintenance costs are incurred to ensure that numerous parts of the plant are corrosion resistant. In addition, the aluminum chloride catalyst, which is dissolved or suspended in the reaction mixture, must be removed from the product stream and disposed. Removal is effected by neutralization via an elaborate series of aqueous and caustic washes. Increased expenditures are required for the catalyst preparation and neutralization stages of the plant. As a further disadvantage, an aluminum-containing waste is obtained whose disposal can create significant environmental problems.
It is known that the alkylation of benzene with ethylene to form ethylbenzene can be catalyzed by a solid acid, specifically, an acidic zeolite. Many zeolites have been disclosed for alkylation, including mordenite, ZSM-5, ZSM-11, ZSM-12, Y, omega, EU-1, NU-87, beta, MCM-22, MCM-36, MCM-49, MCM-56, MCM-58, and SSZ-25. With regard to the use of dealuminated acid mordenite zeolite in the ethylation of benzene, reference is made, for example, to U.S. Pat. Nos. 5,004,841, 5,198,595, and 5,243,116. With regard to the use of zeolite ZSM-5, reference is made to U.S. Pat. No. 4,665,255. For alkylations with zeolites ZSM-11 and ZSM-12, reference is made to U.S. Pat. No. 4,358,362. With regard to the use of zeolite EU-1, reference is made for example to EP-A1 -0,537,389; for zeolite NU-87 to U.S. Pat. No. 5,178,748; for zeolite beta, reference is made, for example, to U.S. Pat. No. 4,891,458 and to U.S. Pat. No. 5,081,323; for zeolite Y to U.S. Pat. No. 4,459,426 and to U.S. Pat. No. 4,798,816 and to U.S. Pat. No. 4,876,408; for zeolite MCM-22 to U.S. Pat. No. 4,992,606; for zeolite MCM-36 to U.S. Pat. No. 5,258,565; for zeolite MCM-49 to U.S. Pat. No. 5,236,575 and PCT publication WO 94/29245; for MCM-56 to U.S. Pat. No. 5,453,554; for MCM-58 to WO 95/11196; and for SSZ-25

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K. Weissermel and H.-J. Arpe, Industrial Organic Chemistry, 2nd ed., VCH Verlagsgesellschaft, Weinheim, Germany, 1993, pp. 333-336.

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