Effects of La- and Ba- based perovskites coated on perovskite membranes on oxygen permeation

Abstract

The surface modification of substrate perovskite membranes with a porous layer was performed by coating of the catalytic perovskite compounds: La₁₋ₓSrₓCoO₃₋δ, La₁₋ₓSrₓFeO₃₋δ, Ba₁₋ₓ SrₓCoO₃₋δ, และ Ba₁₋ₓ Srₓ FeO₃₋δ or abbreviated as LSC, LSF, BSC, and BSF, respectively where x = 0.2 – 0.6. These perovskites were synthesized by a modified citrate method. Amount of strontium (x) affecting the crystallines structure of the perovskite compounds were studied. The catalytic perovskite layer was coated on both surfaces of the sintered membrane by a screen-printing method and repeated twice. Post heat treatment was conducted to control the porosity of the coating layer at 800-1,000 ℃. The substrate membranes were using La₀ ̣₈Sr₀ ̣₂Co₀ ̣₆ Fe₀ ̣₄ O₃₋δ, La₀ ̣₆ Sr₀ ̣₄Ga₀ ̣₃Fe₀ ̣₇ O₃₋δ, and Ba₀ ̣₅Sr₀ ̣₅Co₀ ̣₈ Fe₀ ̣₂O₃₋δ or abbreviated as LSCF8264, LSGF6437, and BSCF5582. The formation of catalytic perovskite powders and coated membrane were confirmed by XRD. The morphology of the coated membranes was investigated by SEM. The results indicated that in the sinter temperature at 1,000 ℃, the porous layer was formed. The oxygen desorption of the perovskite compounds were determined by TGA and O₂-TPD. Experimental results of TGA indicated that the amount of oxygen desorbed from the BSF55 catalyst is higher (2.192 %) than that of the other catalytic compounds. By introducing a highly oxygen desorbed BSF55 coating on the BSCF5582 membrane, significant promotion in the oxygen permeation fluxes could be obtained.