Investigation of chemical stability and oxygen permeability of perovskite-type Ba0.5Sr0.5Co0.8Fe0.2O3 − δ and BaCo0.7Fe0.2Nb0.1O3 − δ ceramic membranes

In this paper, two kinds of perovskite-type mixed conductor materials, Ba0.5Sr0.5Co0.8Fe0.2O3 − δ and BaCo0.7Fe0.2Nb0.1O3 − δ, were prepared by solid state synthesis. By combination of thermal gravimetric analysis, XRD and SEM, the high-temperature chemical stability of these two materials in pure Ar, 10% CO2 + Ar and 40% H2 + Ar atmosphere was studied. In addition, oxygen permeation tests were also conducted in order to study the two materials' long term stability under service condition of coke oven gas (COG) partial oxidation reforming. The results show that BaCo0.7Fe0.2Nb0.1O3 − δ material, in which Ba occupied all A-site and B-site is partly substituted by a small amount of Nb, has a better chemical and structural stability than Ba0.5Sr0.5Co0.8Fe0.2O3 − δ at high temperature under rather high oxygen concentration gradient through the membrane. At 875 °C, when COG flow rate was 88 ml/min and air flow was fixed at 76.89 ml/min, oxygen permeation flux through a BaCo0.7Fe0.2Nb0.1O3 − δ membrane of 1 mm in thickness reached 11.5 ml/min1 cm2, which could meet the industrial conditions of the COG partial oxidation reforming in industrial applications.

Research Highlights
► BCFN sample shows a high decomposition temperature in strong reduction atmosphere.
► BCFN’s crystal structure annealed in 10% CO2 + 90% Ar was more stable than BSCF’s.
► Nb in B-site plays a positive role in improving the stability of BCFN.
► Both membranes were increasing oxygen permeation flux with COG flow rate increase.