Alkylation of toluene with propene using zeolite catalysts

Abstract

The catalytic activity of Y-type zeolite for the alkylation reaction of toluene with propene is strongly dependent on the degree of ion-exchange and on the calcination temperature. The activity increases as the sodium ions in Na-form Y zeolite are replaced by hydrogen ions up to at least 90% cation exchange. Optimum activity occurs at activation temperatures around 400 °C when the Brønsted acidity is at a maximum. Ortho-para substitution always predominates, but at low activation temperatures (<400 °C) the p isomer is preferred. This preference is reduced with increasing activation temperature, accompanied by a marked increase in the proportion of the m isomer. Present results indicate that the alkylation proceeds by a carbonium ion mechanism involving Brønsted acid sites on the zeolite surface. There is no correlation between the catalytic activity of the zeolite and its electron-transfer properties. The isomeric composition of the products suggests, however, that the selectivity of the catalysts is a function of their Lewis acidity. These findings, therefore, provide further evidence for the dual nature of zeolite catalysts.