Development of CVD Silica Membranes Having High Hydrogen Permeance and Steam Durability and a Membrane Reactor for a Water Gas Shift Reaction

Water gas shift reaction of carbon monoxide (CO) with membrane reactors should be a promising method for hydrogen mass-production because of its high CO conversion, high hydrogen purity and low carbon dioxide emission. For developing such membrane reactors, we need hydrogen permselective membranes with high hydrogen permeance with order of 10^-6 mol m^-2 s^-1 Pa^-1 at 573 K and high steam durability. In this study, we have optimized the kind of substrates, precursors, vapor concentration, and chemical vapor deposition (CVD) time using the counter-diffusion CVD method for developing such membranes. The developed membrane prepared from hexamethyldisiloxane has a hydrogen permeance of 1.29 × 10^-6 mol m^-2 s^-1 Pa^-1 at 573 K and high steam durability. We also conducted water gas shift reactions with membrane reactors installed the developed silica membranes. The results indicated that reactions proceed efficiently with the conversion around 95-97%, hydrogen purity around 94%, and hydrogen recovery around 60% at space velocity (SV) 7000.