Preparation of porous inorganic membranes for hydrogen separation by silica sol-gel and chemical vapor deposition methods

Abstract

In this research, porous inorganic membranes for hudrogen sepration were prepared with alumina support by a multi-step pore modification method. The α-alumina support had an asymmetric structure and average pore size of its skin layer was 80nm. Porous inorganic membranes for $H_2$ separation were made by three consecutive steps ; namely, in-situ silica sol-gel method, silica sol dip-coating method, and Soaking and Vapor Deposition (SVD) method. In order to enhance the selectivity improvement, we used Pd particles in the final step. Although both silica and palladium(Pd) induced the surface diffusion, Pd was more effective for hydrogen selective adsorption than silica. This multistep method produced the porous membranes with a moderate hydrogen selectivity and excellent hydrogen permeability at high temperature(=773K) and at high transmembrane pressure(ΔP=310kPa). The separation factor of hydrogen relative to nitrogen was maintained at about 10 even when the transmembrane pressure was as high as 310kPa, and the hydrogen permeability was still much higher than that of nonporous polymeric membranes.