Co-firing technology for the preparation of asymmetric oxygen transporting membranes based on BSCF and Zr-doped BSCF
Significance: Asymmetric tubular membranes with a length of 450 mm were prepared in one step by co-firing of a green support coated by slurry. BSCF (Ba0.5Sr0.5Co0.8Fe0.2O3-d) and Zr-doped BSCF3Zr (Ba0.5Sr0.5(Co0.8Fe0.2)0.97Zr0.03O3-d) were used for the separation layer as well as for the porous support, latter one together with PMMA microspheres as a pore forming agent. The gas leakage at room temperature was below 0.003 mL STP/(cm2·min). Oxygen fluxes up to 12 mL STP/(cm2·min) were observed at 900°C in vacuo operation mode. The oxygen flux increased with growing driving force but the slope of the curve flattened at higher driving forces probably caused by limiting surface exchange and pressure losses inside the porous support. The oxygen permeation of asymmetric BSCF tubes was s lightly higher compared to BSCF3Zr and exceeded the oxygen flux of a monolithic BSCF membrane by a factor of 4 at comparable operation conditions.