Fabrication and Evaluation of Trimethylmethoxysilane (TMMOS)-Derived Membranes for Gas Separation

Gas separation membranes were fabricated with varying trimethylmethoxysilane (TMMOS)/tetraethoxy orthosilicate (TEOS) ratios by a chemical vapor deposition (CVD) method at 650 °C and atmospheric pressure. The membrane had a high H(2) permeance of 8.3 × 10(−7) mol m(−2) s(−1) Pa(−1) with H(2)/CH(4) selectivity of 140 and H(2)/C(2)H(6) selectivity of 180 at 300 °C. Fourier transform infrared (FTIR) measurements indicated existence of methyl groups at high preparation temperature (650 °C), which led to a higher hydrothermal stability of the TMMOS-derived membranes than of a pure TEOS-derived membrane. Temperature-dependence measurements of the permeance of various gas species were used to establish a permeation mechanism. It was found that smaller species (He, H(2), and Ne) followed a solid-state diffusion model while larger species (N(2), CO(2), and CH(4)) followed a gas translational diffusion model.