Preparation of high-silica faujasites by means of SiCl/sub 4/

The reaction of Y zeolites with SiCl/sub 4/ vapor has been studied. A connection has been established between the temperature at which the zeolites are treated with SiCl/sub 4/ and the degree of dealumination. It has been shown that up to 95% of the Al can be extracted from the framework by means of SiCl/sub 4/ without destroying the crystal structure. Dealumination increases the thermal stability of the framework and the hydroxyl coating of Y zeolites. On reacting with SiCl/sub 4/ some of the Al removed from the framework remains in the specimen and forms stable extralattice compounds. The content of extralattice Al increases with an increase in the Si/Al ration in the initial zeolite.