Comparative study of zeolite catalyzed alkylation of benzene with alcohols of different chain length: H-ZSM-5 versus mordenite

Abstract

Alkylation of benzene with light alcohols offers opportunities for a more environmental friendly gasoline by removing considerable portions of benzene. The performances of ZSM-5 and mordenite zeolites as catalysts were tested in the alkylation reaction of benzene with different light alcohols (methanol, ethanol and isopropanol). The experiments were carried out in a fluidized-bed reactor with a 1/1 mol ratio of benzene/alcohol at 200, 250, 300, 350 and 400°C for 3, 5, 7, 10, 13, 15 and 20s. The reaction temperature, nature of the alcohol molecule and the BrǾnsted to Lewis acid ratio of the catalysts, play an important role in the alkylation reactions. For benzene alkylation with methanol to toluene and xylene (XY), both mordenite and ZSM-5 are active and selective catalysts, while for benzene ethylation to ethylbenzene (EB), ZSM-5 exhibits higher EB selectivity than mordenite. Isopropanol presents higher difficulty to be activated as compared with other alcohols at the higher temperature, while the lower temperature favors benzene isopropylation to cumene over both catalysts. By studying the alkylation of benzene with alcohols of different chain length, it has been found that as the alkyl size (i.e. methyl, ethyl, and propyl) increases, the optimum temperature for alkylation reaction decreases.