Ethylbenzene formation and its conversion towards coke in the side-chain methylation of toluene on a basic X zeolite

Side-chain alkylation of toluene with methanol was realized on a strongly basic X-type zeolite which does not contain Brønsted acid sites under short contact time conditions to reveal primary products of the reaction. The influence of modification of the external surface of the zeolite on catalyst's deactivation was then studied. Ethylbenzene was recognized as a primary product. It appears to be a product of dehydrocondensation of the toluene methyl group with methanol. Further transformation of alkylaromatics through the consecutive upbuilding of alkyl chain of alkylaromatics by dehydrocondensation with alcohol followed by cyclization and dehydrogenation of the cycle has been proposed as a mechanism of coke formation in toluene methylation on the basic zeolite catalysts which contain no Bronsted acid sites. A negative role of active sites of the outer surface in deactivation was shown, and modification with ammonium hexafluorosilicate has been proposed to reduce coke formation on the outer surface.