Catalytic behavior of a mixed conducting oxygen-permeable membrane reactor for methane oxidation

A mixed conducting perovskite-type Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ ceramic membrane reactor was applied for the activation, of methane, the membrane reactor served as oxygen provider and OCM catalyst at the same time. The oxygen permeability of the membrane increased with the increase of temperature or oxygen partial pressure at the oxygen-rich membrane side (Po₂′)- At 850°C and under air/He oxygen partial pressure gradient, Jo₂ reached about 1.2 mL/(cm².min) for a 1.5 mm thickness membrane. The membrane had catalytic activity for the conversion of methane to ethane and ethylene with C₂ selectivity up to 40%-70%, albeit that the conversions were low, typically between 0.5%-3.5% at 800°C-900°C. Large amount of unreacted molecule oxygen was found in the eluted gas, which led to the relatively low C₂ selectivity due to the noncatalytic homogeneous reaction of methane and carbon-contained products with molecule oxygen. The oxygen permeation flux at the OCM reaction mode increased only slightly compared with that under non-reactive air/He oxygen gradient, it is much different from that at POM reaction mode, the oxygen permeation flux at POM mode increased about ten folds than that at air/He oxygen gradient.