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Benzylation of toluene by benzyl chloride over protonic zeolites

1993; Elsevier BV; Volume: 100; Issue: 1 Linguagem: Inglês

10.1016/0926-860x(93)80116-8

1873-3875

Bernard Coq, Valérie Gourves, François Figuéras,

Catalysis and Oxidation Reactions

The benzylation of toluene with benzyl chloride was studied at 383 K in the liquid phase on different protonic zeolites: H-ZSM-5, H-BETA and HY. Monobenzylation to benzyltoluenes is the main reaction, usually higher than 90% selectivity when a toluene/benzyl chloride molar ratio of 5 is used. Secondary reactions to dibenzyl- and tribenzyltoluenes occur to various extent depending on the reaction conditions and catalysts. The most active catalysts, and the most selective to monobenzylation, are those possessing mesopores in the 30–200Årange: H-BETA and dealuminated HY (Si/Al = 20). On these zeolites it is proposed that intracrystalline catalysis occurs, shape selectivity then preventing secondary reactions. At variance, on the other zeolites, H-ZSM-5 and nondealuminated HY, the reaction takes place at the external surface of the grain yielding a lower activity and selectivity to monobenzylation.