ACIDIC SITES OF STEAMED HY ZEOLITES, ACTIVE FOR BENZENE SELF-ALKYLATION AND HYDROGENATION

HY zeolites, steamed at medium temperature (800 K), catalyze the reactions of benzene self-alkylation and hydrogenation under the pressure of hydrogen. Products of cracking and coke accompany the formation of toluene, methylcyclopentane, and cyclohexane. At 650 K, the maximum conversions in alkylation and hydrogenation exceed 30% and 7% respectively, and remain high for a few days (WHSV = 0.25 h-1). The i.r. study (C2H4, pyridine) shows that active zeolites contain strongly acidic Bronsted sites, characterized by a nu(OH) band at 3600 cm-1, and Lewis sites. A linear correlation exists between the catalytic activity and the number of highly acidic OH groups. This unexpected reaction at 600-650 K may form an interesting catalytic test of very acidic materials.