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

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 separa-tion performance for butane isomers. This strategy can also be applied to the synthesis of other types high-silica zeolite membranes.

Automated summary

In this study, low-cost synthesis of thin ZSM-5 membranes was achieved by using a self-terminating mother liquor with high Si/Al ratio and adjusting the ratio of mother liquor/membrane area to control the thickness. The obtained ultrathin MFI membranes showed excellent separation performance for butane isomers.