Synthesis of thin ZSM-5 zeolite membranes in a self-terminating mother liquor

Abstract

Low-cost synthesis of thin zeolite membranes is extremely desirable, yet challenging. In this study, we realized template-free synthesis of ultrathin ZSM-5 membranes by conventional hydrothermal synthesis on regular ceramic support. The key is to choose a self-terminating mother liquor with high Si/Al ratio. The crystallization process (formation of ZSM-5 zeolite crystals and membrane) in this Al-deficient mother liquor is an Al-driven process. The crystallization led to fast depletion of Al in the mother liquor which triggered the termination of crystallization process in this template-free mother liquor. Therefore, the thickness of ZSM-5 membrane can be controlled easily by adjusting the ratio of mother liquor/membrane area, which is much simpler than membrane synthesis in conventional mother liquor. The obtained ultrathin MFI membranes exhibited outstanding separation performance for butane isomers. This strategy can also be applied to the synthesis of other types high-silica zeolite membranes.