Dimethoxydimethylsilane-derived silica membranes prepared by chemical vapor deposition at 973 K exhibiting improved thermal/hydrothermal stability

Abstract

With the aim of developing thermally/hydrothermally stable silica membranes for H2 separation, dimethoxydimethylsilane-derived silica membranes were prepared via chemical vapor deposition (CVD) at various temperatures. This process employed a substrate having an intermediate layer with a gallium-loaded γ-alumina coating that had been calcined at 1073 K. The data demonstrate that this intermediate layer was itself thermally stable at 1073 K and hydrothermally stable at 973 K. A systematic evaluation of membrane performances under thermal/hydrothermal conditions confirmed that membranes prepared at 973 K were more stable than those fabricated at 873 K under dry conditions. In addition, the loss in H2 permeance under hydrothermal conditions was lower in the case that the CVD temperature was 973 K. Hence, to ensure stability, the temperature at which such membranes are employed should be lower than the CVD processing temperature.