HYDROGENATION AND ISOMERIZATION OF HYDROCARBONS ON MODIFIED ZEOLITE CATALYSTS

An investigation has been made of the influence of the silica modification of Pd-zeolite catalysts based on H forms of Y zeolites, dealuminized mordenite and TsVM zeolites on their physicochemical properties, and also on the activity and selectivity of hydroisomerization of a pentane-benzene mixture. Tetraethoxysilane and hexamethyldisiloxane were used as the source of silica. It was shown that the physicochemical and catalytic properties of modified zeolite catalysts depend on the type of initial organosilicon compound. The tetraethoxysilane modification of a catalyst based on HM leads to a reduction in adsorption capacity and counterdiffusion in the n-hexane-benzene system and in activity in the hydroisomerization of a pentane-benzene mixture. Here there is also a reduction in the degree to which benzene retards the isomerization of n-pentane. At the same time, the hexamethyldisiloxane modification of this catalyst results in a small reduction in the adsorption capacity of the specimen, while its activity in the hydroisomerization of a pentane-benzene mixture remains unchanged. It is assumed that the different influence of the given organosilicon compounds is due to the position of the SiO2 formed in pores of the zeolite (in the case of tetraethoxysilane) or on the external surface of its crystallites (in the case of hexamethyldisiloxane modification).