DESIGN OF SILICA NETWORKS USING ORGANIC-INORGANIC HYBRID ALKOXIDES FOR HIGHLY PERMEABLE HYDROGEN SEPARATION MEMBRANES

Sol-gel method was applied for the preparation of organic-inorganic hybrid silica membranes. 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) and bis (triethoxysilyl) ethane (BTESE) were used as silica precursors instead of tetraethoxysilane (TEOS) for the preparation of organic-inorganic hybrid silica membranes. Molecular weight of hybrid silica polymer was successfully controlled by reaction time and reaction temperature. Single gas permeation characteristics for hybrid silica membranes were examined to discuss the effect of silica precursor on amorphous silica networks. Pore size distribution suggested hybrid silica membranes derived by BTESE and TMCTS had loose amorphous silica structures compared to silica membranes derived by TEOS. Hybrid silica membranes derived by BTESE and TMCTS showed high hydrogen permeance (0.3-1 x 10(-5) mol.m(-2).s(-1).Pa(-1)) with high selectivity of H(2) to SF(6) (H(2)/SF(6) permselectivity: similar to 1,000) and low H(2) to N(2) permselectivity (similar to 10). It was found that hybrid silica membrane derived by TMCTS had high hydrothermal stability due to the presence of CH(3) groups in amorphous silica networks.