Effect of the <i>B</i>-Site Composition on the Oxygen Permeability and the CO₂ Stability of Pr_0.6Sr_0.4Co_<i>x</i>Fe_1–<i>x</i>O_3−δ (0.0 ≤ <i>x</i> ≤ 1.0) Membranes

Abstract

Dense single-phase perovskite-type Pr 0.6 Sr 0.4 Co x Fe 1– x O 3−δ (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 CO 2 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 CO 2 -containing atmosphere were analyzed using X-ray diffraction. The highest oxygen permeation flux was observed for Pr 0.6 Sr 0.4 CoO 3−δ with 1.57 cm 3 (STP) min –1 cm –2 and 1.37 cm 3 (STP) min –1 cm –2 at 1000 °C under air/He and air/CO 2 gradients, respectively. Furthermore, the effect of CO 2 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 CO 2 exposure and their microstructures were less affected by CO 2 . The partial oxidation of methane (POM) to syngas was successfully performed for more than 80 h at 950 °C using a PSCF membrane with a Co content of x = 0.2. The POM reaction shows an average CH 4 conversion rate of >98% and a CO selectivity of >95%.