Faujasite aluminum-deficient

A modification of the above cyclic method has proved more effective in the dealumination of Y zeolites. An almost aluminum-free, Y-type structure was obtained by using a process involving the following steps a) calcination, under steam, of a low-soda (about 3 wt.% Na O), ammonium exchanged Y zeolite b) further ammonium exchange of the calcined zeolite c) high-temperature calcination of the zeolite, under steam d) acid treatment of the zeolite. Steps a) and c) lead to the formation of ultrastable zeolites USY-A and USY-B, respectively. Acid treatment of the USY-B zeolite can yield a series of aluminum-deficient Y zeolites with different degrees of dealumination, whose composition depends upon the conditions of the acid treatment. Under severe reaction conditions (5N HC1, 90°C) an almost aluminum-free Y-type structure can be obtained ("silica-faujasite") (28,29). 

Thomas et al. (39,41) recorded the Si-NMR spectrum of an aluminum-deficient Y zeolite prepared by reacting NaY zeolite with SiCl vapors. The spectrum showed a single sharp peak, characteristic of Si(0 Al) groupings, and indicative of an essentially luminum-free faujasite structure. 

The Nature of Ultrastable Faujasite and Aluminum-Deficient Zeolite Y... 

Jacobs and Uytterhoeven studied the nature of deep-bed calcined ammonium zeolite Y and aluminum-deficient zeolite Y, the latter prepared by the H4EDTA technique 30). They concluded that the stability of ultrastable faujasite was imparted only by cationic aluminum and that aluminum deficiency in itself did not contribute to stability. Their conclusion regarding aluminum deficiency was made on the basis of H4EDTA-... 

G.T. Kerr and G.F. Shipman, The Reaction of Hydrogen Zeolite Y with Ammonia at Elevated Temperatures. J. Phys. Chem., 1968, 72, 3071-3072 G.T. Kerr, Chemistry of Crystalline Aluminosilicates. V. Preparation of Aluminum-Deficient Faujasites. J. Phys. Chem., 1968, 72, 2594-2596. 

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