Hydrogen Separation in Hydrogen–Methylcyclohexane–Toluene Gaseous Mixtures through Triphenylmethoxysilane-Derived Silica Membranes Prepared by Chemical Vapor Deposition

Amorphous triphenylmethoxysilane-derived silica membranes were prepared by chemical vapor deposition to demonstrate excellent hydrogen separation performance from gaseous mixtures containing methylcyclohexane (MCH) and toluene (TOL). Pure H 2 permeances were on the order of 10 –6 mol m –2 s –1 Pa –1, while the single gas permeances of SF 6, TOL, and MCH were all on the order of 10 –11 mol m –2 s –1 Pa –1, regardless of the ranges of pressure difference and temperature (0.1–0.5 MPa and 373–573 K). This agrees with the order of kinetic diameters for these gaseous molecules, showing high selectivity of hydrogen over the hydrocarbons. The influence of the coexisting MCH and TOL on H 2 separation performance through the same membrane was investigated in the gaseous mixtures after eliminating the effect of water molecules. Similar negative effects were observed for MCH and TOL on the H 2 separation properties, with the influence of TOL being slightly higher than that of MCH for H 2 –X (X = MCH, TOL) binary mixtures. Moreover, such the silica membrane exhibited high hydrogen separation performance and good stability in the H 2 –MCH–TOL ternary gaseous mixtures under operating conditions, which would have potential application to extract high purity hydrogen over 99.99% in membrane reactors. The membrane underwent eight mixtures exposure–regeneration cycles and exhibited stable medium-term running for over 25 days including gas-exchanging cycles and temperature cycles at 573–373 K.