ALKYLATION OF AROMATICS ON B-CONTAINING ZSM-5 ZEOLITES

The catalytic activity of ZSM-5 zeolites, modified with boric acid, ha s been studied in benzene and toluene alkylation by ethylene. The conc entration of acid sites of different nature in these zeolites was char acterized by IR spectroscopy of OH-groups and adsorbed CO. A decrease of the concentrations of both strong protic and non-protic sites was s hown to occur upon modification. Secondary acid sites are assumed to a ppear 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 zeolite s are considered in relation to the nature and concentration of the ac id sites.