Improving the oxygen permeability of barium or lanthanum-based perovskite membranes by surface-coating with catalysts

Abstract

The effect of SrCoFeOx (SCF), La₀₁Sr₀.₉Co₀.₉Fe₀₁O₃ (LSCF) and SrCo₀.₄Fe₀.₅Ni₀₁O₃ (SCFN) thin layers, prepared by modified citrate method, coating on oxygen permeation flux through dense Ba₀.₅Sr₀.₅Co₀.₈Fe₀.₂O₃ (BSCF) membranes and BaCo₀.₇Fe₀.₂Nb₀.₁O₃ (BCFN) membranes, synthesized via solid state method, was investigated. Unfortunately, the relative density of prepared BCFN membrane (79.28%) was quite lower than the required 90% for gas permeation membrane; therefore, only BSCF membrane was further studied. The catalyst powders were coated on one or both surfaces of dense BSCF membranes. The oxygen permeation flux of membranes was measured in the temperature range of 700-1000°C. The results show that the oxygen permeation fluxes of most coated membranes were higher than the flux of uncoated BSCF membrane. Comparing the effect of single-coating on air side, coating of SCF showed higher flux than coating with LSCF and SCFN. On the other hand, comparing the effect on He side, coating with SCFN gave higher flux than LSCF and SCF. Furthermore, double coating with SCF on air side and with SCFN on He side increased the flux of a single-coating and has good oxygen permeation stability at 850°C for at least 100h. The chemical compatibility of membrane and catalysts was tested by firing at high temperature for 10 h. BSCF membrane has good compatibility with SCF and SCFN at 850°C and with LSCF at 900°C.