Polymer derived ceramic membranes for gas separation

Ceramic membranes based on polymer derived ceramics (PDCs) like silicon oxycarbide (SiOC) and silicon carbonitride (SiCN) offer an attractive combination of physical and chemical properties like chemical inertia, high mechanical strength and high temperature resistance. SiOC and SiCN membranes were deposited as thin layers by coating on top of tubular asymmetric porous ceramic substrates starting from a polymeric precursor solution followed by crosslinking and pyrolysis above 600 °C in inert atmosphere. High ideal permselectivities were achieved at 300 °C. SiOC membrane showed nearly ten times higher permeances of hydrogen to carbon dioxide and therefore possessed molecular sieving properties in separation of H2/CO2. A comparable SiCN membrane had a very low H2/CO2 ideal permselectivity bu t promising results for the other ideal permselectivities.