templated nanostructure silica membrane versus template-free one: synthesis, characterization, and performance for hydrogen separation

An experimental study was carried out to investigate synthesis and performance of the mtes (methyltriethoxysilane) templated and template-free nanostructure silica membranes for hydrogen separation. the permeance of hydrogen, carbon dioxide, and nitrogen pure gases and permselectivity and separation factor of gas mixtures were investigated at 25° c, 100° c, and 200° c. activated molecular sieve with positive and negative signs and knudsen disusion were respectively the dominant transport mechanisms in hydrogen, carbon dioxide, and nitrogen gas molecules permeances. although the hydrophobic property of templated membrane is a good option for gas separation in hydrothermal conditions, the dense structure of the membrane results in lower permeance and permselectivity in comparison with template-free one. hydrogen permeance at 200° c and 3 bar, which was measured as 30:5*10^-8 mol m^-2 pa^-1 s^-1 for template-free silica membrane, decreased to 2:37*10^-8 mol m^-2 pa^-1 s^-1 for mtes templated silica membrane. permselectivity and separation factor of h2/n2 in the same conditions, which were respectively measured as 31.2 and 21 for template-free membrane, reached 21.5 and 8 for templated membrane. in addition, h2/co2 permselectivity in the same conditions was measured as 23.4 and 13.9 for template-free and templated membranes, respectively.