Preparation and gas permeation of supported γ-Al2O3 membranes used as substrate layer for microporous membranes

γ-Al2O3 membranes were successfully deposited on the top of porous α-Al2O3 support by sol-gel process and characterized by means of XRD, SEM, N2 adsorption and gas permeation. The γ-Al2O3 membranes, free of pin-holes and cracks, adhere tightly to the supports and have a thickness of about 7 μm. When sintered at 400°C, γ-Al2O3 membranes have a narrow pore size distribution, with a pore diameter of 3.6 nm, and the transport of both H2 and CO2 in supported γ-Al2O3 membrane is governed by Knudsen mechanism, with H2 permeance of 3.3 × 10-6 molm-2 Pa-1 s-1 and H2/O2 permselectivity close to the ideal Knudsen value at 50°C. The γ-Al2O3 membranes are suitable for being used as the substrates of microporous membranes.