ALKYLATION OF AROMATICS ON P-CONTAINING ZSM-5 ZEOLITES

The catalytic activity of ZSM-5 zeolites, modified with phosphorus com pounds, has been studied in benzene and toluene alkylation by ethylene . Concentration of acid sites of different nature in the samples was c haracterized by IR spectroscopy of OH-groups and adsorbed CO. Modifica tion was shown to decrease the concentrations of both strong protic an d non-aprotic sites. New acid sites are assumed to appear in P-contain ing zeolites. The strength of acid.sites in the zeolites is supposed t o follow the sequence:[[SiOAl]H]>>[POH]>>[MgOH. Activity and regiosele ctivity of P-containing zeolites are considered to depend on the natur e and concentration of the acid sites.