Synthesis of ZIF-8 Membranes on gamma-Alumina Supports forSeparation of Propylene/Propane Gas Mixture

Zeolitic imidazolate framework-8 (ZIF-8) mem-branes have shown promising potential for the separation ofindustrially important propylene/propane mixtures. For industrialapplications, it is necessary to synthesize a thin and defect-freeZIF-8 membrane with good integrity on scalable supports. In thiswork, we report the synthesis of ZIF-8 membranes on the sol-gelderived mesoporous gamma-alumina layer coated on top of the alpha-alumina support. Thin (2.5 mu m), high quality, and stable ZIF-8membranes can be grown on the gamma-alumina support grafted with 3-glycidoxypropyltrimethoxysilane (GLYMO) by the seeded secon-dary growth method. Propylene/propane equimolar mixtureseparation experiments were conducted to test the separationperformance of membranes. Compared to the ZIF-8 membraneson the bare macroporous alpha-alumina support, ZIF-8 membranes prepared on the gamma-alumina coated alpha-alumina support show muchbetter separation characteristics, with a maximum propylene/propane separation factor of 225 and propylene permeance of 9.65x10-9mol m-2s-1Pa-1. The ZIF-8 membrane synthesized on the scalable gamma-alumina coated alpha-alumina support exhibits separationcharacteristics and stability similar to the best-performing ZIF-8 membranes on alumina supports with complex synthesis proceduresdifficult to scale up.