Partial oxidation of methane (CH4) and oxygen permeation in a dense SrCoFeOx disk membrane reactor were studied with the reducing side of the membrane packed with different catalysts (catalyst support gamma-Al2O3, La0.6Sr0.4Co0.8Fe0.2O3-delta, and 10 wt % Ni/gamma-Al2O3) of increasing reaction activities for CH4 oxidation. The influence of temperature, flow rates, and inlet CH4 concentration (diluted with helium) on the performance of the different membrane reactors was investigated. The oxygen permeation flux and CH4 conversion increased in the following order: gamma-Al2O3 < La0.6Sr0.4Co0.8Fe0.2O3-delta < 10% Ni/gamma-Al2O3. The membrane reactor with the reforming catalyst of 10 wt % Ni/gamma-Al2O3 had the highest CH4 conversion (similar to 90%), CO selectivity (97%), and oxygen permeation flux (2.40 mL/(cm(2) min)) at 900 degrees C. The improvement of the oxygen permeation through the membranes with different catalysts emphasizes the effect of the CH4 oxidation reaction rate on the reducing side of the membrane on the oxygen permeation flux through the mixed-conducting ceramic membranes. Under identical conditions, the oxygen permeation flux through mixed-conducting ceramic membrane with a reducing gas is a strong function of the catalytic activity for the oxidation of the reducing gas.