Modification of pore size of MFI-type zeolite by catalytic cracking of silane and application to preparation of H2-separating zeolite membrane

Catalytic cracking of silane (CCS) is proposed as a new method for modifying the effective pore opening of a zeolite. In this method, first silane compounds 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 calcination 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 powdery MFI-type zeolite, the adsorption capacity of benzene is markedly reduced, but that of CO2 is maintained constant. Furthermore, the proposed CCS method was applied to reduce the pore diameters of an MFI-type zeolite membrane. By use of the membrane, experiments of separating H-2 from a mixture gas containing H-2 and N-2 or O-2 were conducted in a flow system. The membrane 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 Science B.V. All rights reserved.