Mechanism of gas separation through amorphous silicon oxycarbide membranes 

Polymer-derived amorphous silicon oxycarbide (SiOC) ceramics are designed for hydrogen separation at high temperatures. To form amorphous SiOC top-coating with the thickness of about 300 nm, tubular porous g-Al2O3/a-Al2O3 substrates with gradient porosity are threefold coated by vinyl-functionalized polysiloxane and pyrolyzed at 700 °C under argon. N2-physisorption measurement confirms formation of microporous material with a specific surface area of about 400 m2 g-1. Single gas permeance characterization of the SiOC membrane at 300 °C reveals H2/CO2 and H2/SF6 ideal permselectivities of about 10 and 320, respectively. The experimental gas permeance data are modeled using solid-state diffusion (for He and H2) and gas translational diffusion (for CO2 and SF6) mechanisms.