Ceramic materials for H2 transport membranes applicable for gas separation under coal-gasification-related conditions

This work focuses on the synthesis, characterization and testing of mixed protonic–electronic conducting membrane materials for H2 separation from gas mixtures capable of operating in a membrane reactor at temperatures higher than 600 °C. La5.5WO12−δ and selected substituted barium zirconates with stoichiometries BaCe0.5Zr0.4Y0.1O3−δ and BaCe0.2Zr0.7Yb0.08Ni0.02O3−δ were therefore characterized and tested under coal-gasification-related conditions at 600–900 °C. Sintered samples of the synthesized substituted barium zirconates were characterized by measuring the total conductivity and the thermal expansion coefficients. Also particle size distributions, BET surface-areas and elemental analysis of the starting powders, including commercial La5.5WO12−δ were specified. The compounds were exposed to syngas with steam, as well as to an atmosphere mainly consisting of CO2. The microstructure and phase composition of the membrane materials were studied by SEM, EDX and XRD before and after exposure. BaCe0.2Zr0.7Yb0.08Ni0.02O3−δ shows a very promising chemical stability from 600 °C to 900 °C and La5.5WO12−δ at 900 °C.