Preparation of microporous silica membranes for gas separation

Abstract

Microporous silica membranes for hydrogen separation were prepared on a gamma -alumina coated a-alumina tube by sol-gel method. The reactants of sol-gel chemistry were tetraethoxysilane (TEOS) and methacryloxypropyltrimethoxysilane (MOTMS). The silane coupling agent, MOTMS, was added as a template in order to control the pore structure to the silicon alkoxide. TEOS. In particular, the microporous membranes were prepared by changing the molar ratio of MOTMS with respect to other substances, and their pore characteristics were analyzed. Then, the effects of thermal treatment on the micropore structure of the resulting silica membranes were investigated. The pore size of the silica membrane prepared after calcination at 400-700 degreesC was in the range of 0.6-0.7 nm. In addition, permeation rates through the membranes were measured in the range of 100-300 degreesC using H-2, CO2, N-2, CH4, C2H6, C3H6 and SF6. The membrane calcined at 600 degreesC showed a H-2 permeance of 2x10(-7)-7x10(-7) molm(-2)s(-1)Pa(-1) at permeation temperature 300 degreesC. and the separation factors for equimolar gas mixtures were 11 and 36 for a H-2/CO2 mixture and 54 and 132 for a H-2/CH4 mixture at permeation temperatures of 100 degreesC and 300 degreesC, respectively.