COMPOSITION, ACIDITY, AND CATALYTIC ACTIVITY OF HIGH-SILICA FAUJASITES

The heats of adsorption of ammonia and the catalytic activity in isooc tane cracking are reported for high-silica Y zeolites. The catalytic a ctivity of samples with different aluminum contents passes through the maximum at 25 - 30 atoms A1 per unit cell. The increase in catalytic activity is associated with the appearance of strong acid sites (q(NH3 ) > 120 kj/mol). The effect of acidity on the activity of dealuminated zeolites is explained in terms of isolated acid-site generation. It i s postulated that nonframework Al atoms are catalytically insignifican t.