Abstract: 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/CO₂ separation factor of 6.0 at 200℃, and the hydrogen
permeance shows little change and the H₂/CO₂ 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.

Key words: silica membrane, hydrophobicity, hydrothermal stability, hydrogen separation, sol-gel process