Oxygen permeation and stability study of La0.6Sr0.4Co0.8Ga0.2O3−δ (LSCG) hollow fiber membrane with exposure to CO2, CH4 and He

Abstract

La0.6Sr0.4Co0.8Ga0.2O3−δ (LSCG) perovskite material has been synthesized and fabricated into oxygen permeating hollow fiber membranes. Oxygen permeation from 100mLmin−1 of air at 650°C to 950°C were tested with 100mLmin−1 of pure He, CH4 and CO2 as sweep gases. The maximum O2 permeation flux at 950°C was in the order of CH4 followed by He and CO2 at 7.45mLmin−1cm−2, 3mLmin−1cm−2 and 2.4mLmin−1cm−2. Sweeping with CH4 resulted in the highest flux due to increase in surface exchange reaction whereas the lowest flux was attained for CO2 sweep due to formation of SrCO3. An 80h CO2-stability test was then conducted at 900°C and 800°C. In this CO2-stability study, He and CH4 were intermittently used as sweep gases in order to study their effect on the O2 flux of the CO2 swept LSCG membrane. Interestingly, the fluxes improved upon exposure to He and CH4. However, after being switched back to CO2 from He sweep, the flux slightly improved initially before stabilizing again to the value prior to He sweep. The impact of switching back from CH4 showed insignificant changes in the stabilized flux compared to the initial value. SEM-EDX characterization of the membrane from the CO2-stability study shows considerable erosion at the wall structure with indication of SrCO3, SrO and CoO phases. However, this did not impede the stability of the fluxes or the integrity of the membrane throughout the 80-h study. In fact, XRD shows that the perovskite structure is maintained despite having lower crystallinity.