Effect of the B-Site Composition on the Oxygen Permeability and the CO2 Stability of Pr0.6Sr0.4CoxFe1-xO3-δ (0.0 ≤ x ≤ 1.0) Membranes

Dense single-phase perovskite-type Pr0.6Sr0.4CoxFe1-xO3-delta (0.0 <= x <= 1.0) membranes (0.6 mm thick) were synthesized via EDTA-citric acid complexing route. Subsequently, the effect of various B-site Co/Fe compositions on oxygen permeability, temperature-dependent CO2 stability, microstructure, and electrical properties of the membranes were studied. The crystal structures and the high-temperature phase stability of the perovskite structure in a CO2-containing atmosphere were analyzed using X-ray diffraction. The highest oxygen permeation flux was observed for Pr0.6Sr0.4CoO3-delta with 1.57 cm(3)(STP) min(-1) cm(-2) and 1.37 cm(3)(STP) min(-1) cm(-2) at 1000 degrees C under air/He and air/CO2 gradients, respectively. Furthermore, the effect of CO2 as the sweep gas on the temperature-dependent oxygen permeability and stability of the membranes was studied. Basically, the membranes with lower Co contents were found to be less susceptible to CO2 exposure and their microstructures were less affected by CO2. The partial oxidation of methane (POM) to syngas was successfully performed for more than 80 h at 950 degrees C using a PSCF membrane with a Co content of x = 0.2. The POM reaction shows an average CH4 conversion rate of >98% and a CO selectivity of >95%.