PHYSICOCHEMICAL AND CATALYTIC PROPERTIES OF A NEW-TYPE OF AS-SYNTHESIZED ALUMINUM-DEFICIENT Y-ZEOLITE

Physicochemical (IR spectroscopy, Al-27 and Si-29 MAS NMR spectroscopy , XRD, adsorption measurements) and catalytic properties of a new type of low-alumina Y zeolite CLAY) prepared by direct synthesis (SiO2/Al2 O3 molar ratios 5.5-7.2) without using any templating agents or post-s ynthesis dealumination procedures were studied in comparison with the conventional or dealuminated Y zeolites. The low-alumina NaH-LAY zeoli tes are characterized by the higher thermal stability of acidic OH gro ups as compared with dealuminated Y zeolite. The unit cell parameter m easured by XRD remains virtually unchanged and close to 2.463 nm for N a-LAY zeolite with SiO2/Al2O3 ratios of 5.85-7.2. Extraframework alumi nium was not found in decationized LAY zeolite samples by Al-27 MAS NM R until the residual Na2O content reached values below 1 wt.%. In addi tion, it is possible to tune the activity in the catalytic cracking of n-hexane by varying the extent of decationization. The content of iso mer products increases with a growth of the residual Na2O content in L AY zeolite. Introduction of this new zeolite into the cracking catalys ts provides the maximum yield of gasoline at lower catalyst/feed ratio s, compared to catalysts containing dealuminated Y zeolites. The case of the commercial use of the NaH-LAY zeolite is discussed. (C) 1998 El sevier Science B.V. All rights reserved.