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

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