Preparation, Characterization and Hydrothermal Stability of Hydrophobic Methyl-modified Silica Membranes

Methyl-modified silica membranes were prepared by acid catalysed co-hydrolysis and condensation reaction of tetra-ethylortho-silicate(TEOS) and methyl-tri-ethoxy-silane(MTES) in ethanol and characterized by TGA,FTIR and gas permeation. The hydrophobicity of modified silica membranes increases with MTES/TEOS molar ratio and almost no water can be adsorbed on the surface of the membranes with MTES/TEOS molar ratio higher than 0.8. For the modified silica membranes with METS/TEOS molar ratio of 1, the hydrogen transport is activated by temperature with a H2 flux of 6.0×10-7mol·m-2·Pa-1·s-1 and H2/C02 separation factor of 6.0 at 200℃, and the hydrogen permeance shows little change and the H2/C02 separation factor increases after aging at 200℃ and a water vapor pressure of 3564Pa for 110 hours. It's shown that CH3-modified silica membranes are more hydrothermally stable than the unmodified silica membranes.