Synthesis of ZIF-8 Membranes on γ-Alumina Supports for Separation of Propylene/Propane Gas Mixture

Zeolitic imidazolate framework-8 (ZIF-8) membranes have shown promising potential for the separation of industrially important propylene/propane mixtures. For industrial applications, it is necessary to synthesize a thin and defect-free ZIF-8 membrane with good integrity on scalable supports. In this work, we report the synthesis of ZIF-8 membranes on the sol–gel derived mesoporous γ-alumina layer coated on top of the α-alumina support. Thin (2.5 μm), high quality, and stable ZIF-8 membranes can be grown on the γ-alumina support grafted with 3-glycidoxypropyltrimethoxysilane (GLYMO) by the seeded secondary growth method. Propylene/propane equimolar mixture separation experiments were conducted to test the separation performance of membranes. Compared to the ZIF-8 membranes on the bare macroporous α-alumina support, ZIF-8 membranes prepared on the γ-alumina coated α-alumina support show much better separation characteristics, with a maximum propylene/propane separation factor of 225 and propylene permeance of 9.65 × 10–9 mol m–2 s–1 Pa–1. The ZIF-8 membrane synthesized on the scalable γ-alumina coated α-alumina support exhibits separation characteristics and stability similar to the best-performing ZIF-8 membranes on alumina supports with complex synthesis procedures difficult to scale up.