Development of hydrogen-selective dimethoxydimethylsilane-derived silica membranes with thin active separation layer by chemical vapor deposition

Abstract

Novel hydrogen-selective amorphous silica membranes were developed by chemical vapor deposition (CVD) method using dimethoxydimethylsilane (DMDMS) as the silica precursor. The preparation conditions were optimized by varying the DMDMS saturated vapor concentration in the CVD reactor and the CVD time. The membrane prepared under optimized conditions demonstrated excellent hydrogen-selective performance, exhibiting a hydrogen permeance of 2.8 × 10−7 mol m−2 s−1 Pa−1 at 773 K, which is approximately three times larger when compared with silica membranes prepared with tetramethoxysilane (TMOS). And the ideal selectivity of hydrogen to nitrogen at the same temperature was 2.3 × 103. The estimation of pore size by the normalized Knudsen-based permeance (NKP) method and the structural analysis by XPS indicated that the DMDMS-derived membrane possessed a thinner active separation layer compared with the TMOS-derived membrane, while the pore size was comparable. Thus, membrane thickness was influenced by the slight difference in the chemical structures of the silica precursors, resulting in a higher hydrogen permeance. Finally, excellent hydrothermal stability of the DMDMS-derived membrane was demonstrated.