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Applied Catalysis A: General, Vol.172, No.1, 177-191, 1998
Physicochemical and catalytic properties of a new type of as-synthesized aluminium-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/Al2O3 molar ratios 5.5-7.2) without using any templating agents or post-synthesis dealumination procedures were studied in comparison with the conventional or dealuminated Y zeolites. The low-alumina NaH-LAY zeolites are characterized by the higher thermal stability of acidic OH groups as compared with dealuminated Y zeolite. The unit cell parameter measured by XRD remains virtually unchanged and close to 2.463 nm for Na-LAY zeolite with SiO2/Al2O3 ratios of 5.85-7.2. Extraframework aluminium was not found in decationized LAY zeolite samples by Al-27 MAS NMR until the residual Na2O content reached values below 1 wt.%. In addition, it is possible to tune the activity in the catalytic cracking of n-hexane by varying the extent of decationization. The content of isomer products increases with a growth of the residual Na2O content in LAY zeolite. Introduction of this new zeolite into the cracking catalysts provides the maximum yield of gasoline at lower catalyst/feed ratios, compared to catalysts containing dealuminated Y zeolites. The case of the commercial use of the NaH-LAY zeolite is discussed.
Keywords:FCC CATALYSTS