ZEOLITE SILYLATION FOR THE ENHANCEMENT OF PARA-SELECTIVITY IN TOLUENEALKYLATION WITH ETHYLENE

The effect of zeolite silylation using tetraethyl and tetramethyl orth osilicate on the enhancement of para-selectivity and of yields of p-et hyltoluene in toluene alkylation with ethylene was investigated for di fferent Si loadings. It was found that zeolite silylation caused a sub stantial increase in the selectivity and yield of p-ethyltoluene. Data on changes in sorption capacity, in the number of surface and inner s trong acid OH groups, in the rate of uptake of p-ethyltoluene together with the catalytic activity of zeolite and its deactivation indicate that the silylation is restricted to surface and subsurface zeolite la yers. The enhancement of para-selectivity and yield of p-ethyltoluene are controlled predominantly by changes in geometry of pore openings a nd thus by transport rates of ethyltoluenes.