ALKYLATION OF AROMATICS ON B-CONTAINING ZSM-5 ZEOLITES

The catalytic activity of ZSM-5 zeolites, modified with boric acid, has been studied in benzene and toluene alkylation by ethylene. The concentration of acid sites of different nature in these zeolites was characterized by IR spectroscopy of OH-groups and adsorbed CO. A decrease of the concentrations of both strong protic and non-protic sites was shown to occur upon modification. Secondary acid sites are assumed to appear in the zeolites, and the strength of these sites is supposed to follow the sequence: [[SiOAl]H] >> [POH] > [BOH] greater-than-or-equal-to [MgOH]. The activity and regio selectivity of B-containing zeolites are considered in relation to the nature and concentration of the acid sites.