Modification of pore size of MFI-type zeolite by catalytic cracking of silane and application to preparation of H-2-separating zeolite membrane

Catalytic cracking of silane (CCS) is proposed as a new method for modifyin g the effective pore opening of a zeolite. In this method, first silane com pounds which can penetrate into the pores of the zeolite are introduced and are preadsorbed on active sites within the zeolite, such as acid sites and metal cations. Next, the adsorbed species are cracked catalytically on the sites, leaving coke that contains Si atoms on the active sites. By the cal cination of the coked material, mono SiO2 units are formed on active sites, thereby reducing the size of the pores. When this method is applied to pow dery MFI-type zeolite, the adsorption capacity of benzene is markedly reduc ed, but that of CO2 is maintained constant. Furthermore, the proposed CCS m ethod was applied to reduce the pore diameters of an MFI-type zeolite membr ane. By use of the membrane, experiments of separating H-2 from a mixture g as containing H-2 and N-2 or O-2 were conducted in a flow system. The membr ane showed a high H-2 separation factor of about 90-140 (as compared with 1 .4-4.5 for a non-treated MFI-type zeolite membrane). (C) 2001 Elsevier Scie nce B.V. All rights reserved.