Further performance improvement of Ba0.5Sr0.5Co0.8Fe0.2O3−δ perovskite membranes for air separation

Perovskite BaSrCoFeO (BSCF) is a promising mixed conducting ceramic membrane material for air separation. In this work, BSCF powder was synthesized by a modified Pechini sol-gel technique at relatively lower temperature. The O permeation through a series of BSCF membranes has been tested at different temperatures and various O partial pressure gradients. Theoretical investigation indicated that bulk diffusion and the O exchange reactions on membrane surfaces jointly controlled the O permeation through BSCF membranes with thickness of between 1.1 and 0.75 mm. To further improve the O fluxes, effective efforts are made on membrane thickness reduction and surface modification by spraying porous BSCF layers on both surfaces. When the membrane thickness was reduced from 0.75 to 0.40 mm, the O fluxes were increased by 20-60% depending on the operating conditions. The surface modification further improved the O flux by another 20-40%. The high O fluxes achieved in this work are quite encouraging with a maximum value reaching 6.0 mL min cm at 900 °C.