High silica crystalline zeolites and process for their preparation

Claim 1

A process for increasing the silica to aluminum (Si/Al) mole ratio in the crystal lattice of a crystalline aluminosilicate zeolite, said process comprising: (1) hydrothermally treating said zeilite for a period of time sufficient to effect removal of alumina from said crystal lattice, thereby increasing the Si/Al ratio of the zeilite and forming a non-framework amorphous phase alumina by-product on said zeolite; and (2) extracting the amorphous phase alumina selectively with respect to the alumina in said crystal lattice of said zeolite to produce a zeolite product substantially retaining its degree of framework crystallinity with respect to the dealuminized zeolite produced in step (1), said extracting step being carried out by one of the following processes: a) contacting the treated zeolite of step (1) with a solution of an organic acid selected from the group consisting of Cl x F 3-x COOH, RCF 2 COOH or RCCl 2 COOH, wherein x is 1, 2 or 3 and R is phenyl or an alkyl group having from 1 to 10 carbon atoms, for a sufficient time and under process conditions suitable to remove a substantial portion of the amorphous phase alumina from said zeolite; or alternatively b) loading the treated zeolite of step (1) with an organic blocking agent to block access to the framework aluminum centers of the zeolite, and contacting said blocked zeolite with a solution of an extracting agent for sufficient time and under process conditions suitable to remove a substantial portion of the amorphous phase alumina from said zeolite.