Selective conversion of methanol to p-xylene on modified high-silica zeolites

A procedure was proposed for preparation of p -xylene from a nonhydrocarbon material, methanol, in the presence of a modified ultrasil. It was shown that ultrasils modified by multiple-charge cations actively catalyze synthesis of xylenes from methanol at atmospheric pressure, and their properties can be controlled by varying the nature, charge, and size, as well as the procedure of introduction of the modifier cation. Modification of H-ultrasil with gallium led to enhanced para-selectivity (70%) of the catalysts, which was attributed to an increase in the ratio of the Lewis to Brønsted acid sites and to a decrease in the effective channel diameters of the zeolite.