HYDROGENATION AND ISOMERIZATION OF HYDROCARBONS ON MODIFIED ZEOLITE CATALYSTS

An investigation has been made of the influence of the silica modifica tion of Pd-zeolite catalysts based on H forms of Y zeolites, dealumini zed mordenite and TsVM zeolites on their physicochemical properties, a nd also on the activity and selectivity of hydroisomerization of a pen tane-benzene mixture. Tetraethoxysilane and hexamethyldisiloxane were used as the source of silica. It was shown that the physicochemical an d catalytic properties of modified zeolite catalysts depend on the typ e of initial organosilicon compound. The tetraethoxysilane modificatio n of a catalyst based on HM leads to a reduction in adsorption capacit y 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 isomerizat ion of n-pentane. At the same time, the hexamethyldisiloxane modificat ion of this catalyst results in a small reduction in the adsorption ca pacity of the specimen, while its activity in the hydroisomerization o f 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 t etraethoxysilane) or on the external surface of its crystallites (in t he case of hexamethyldisiloxane modification).