4.3 Shape Selective Alkylation of Aromatics on Metallosilicates

Abstract The alkylations of toluene with methanol and of ethylbenzene with ethanol on metallosilicates having MFI structure were studied. It was found that the primary product in these alkylations was only para isomer, because the formation of ortho isomer could be depressed through the restricted transition state selectivity in the pore of MFI structure. The strength of acid sites on the metallosilicate can be controlled with the kind of trivalent ions introduced into the zeolite framework with a minor change of the effective pore dimension. The highest para selectivity was observed on arsenosilicate with the weak acid sites on which the alkylation can be accelerated but the isomerization of para isomer produced primarily is scarcely promoted. Therefore, it is concluded that the main factor to obtain the high para selectivity of MFI type zeolite catalyst is the strength of the acid sites.