Fabrication And Modification Of Oriented MFI Zeolite Membranes

Zeolite membranes have great application potentials in industry due to theirexcellent separation performance and catalytic ability. In many cases, highly orientedzeolite films exhibit superior performance compared to randomly oriented ones,which has aroused wide-spread interest.Up to present, secondary growth method can be used to prepare zeolitemembranes with excellent continuity and orientation properties. But this method isnot suitable for industrialization for its complication and high costs. Whereashydrothermal synthesis method is a simple process and costs low. However, themembranes prepared by hydrothermal synthesis method usually randomly orientatedon porous α-Al2O3substrates and there is rare report on membranes with continuityand orientation properties. In this work, MFI membranes with a&c-orientation wereprepared on modified porous α-Al2O3substrates using hydrothermal synthesis method.The optimal water content was also investigated to prepare continuous, single layermembranes with a&c-orientation. The preparation of orientated membranes on glassplate was also investigated. At last the mechanism of membrane formation onmodified substrate by hydrothermal synthesis method was discussed.The defects in zeolite membranes, which formed during the preparation processmay be one of the most important obstacles for industrial applications of zeolitemembrane. Substance may go through the membranes directly because of theexistence of defects, which weaken the separation. The existing post-syntheticmodification methods can be assorted into, hydrocarbon impregnation and coking,surface coating, catalytic cracking of silane (CCS), chemical vapor deposition (CVD),chemical liquid deposition (CLD) and sol particles deposition. These methods all getsome effects, especially the last two ones achieve selectively repairation..After trying two modification methods, and eventually proposed one method onthe base of our former works. Furthermore, the silicalite membrane treated by ourmethod was applied to CO2/N2gas separation. The separation factor of CO2/N2, whichwas about1.6for the membrane before modification, could be enhanced to ca.5afterdefect-patching, whereas the CO2permeation flux decreased about50%of the freshmembrane. It is believed that this method is a convenient and feasible approach torepair defects of membrane. Those repair processes will play an important for industrialization of zeolite film on industry application.