Methane combustion on LaSrCeFeO mixed oxides: bifunctional synergistic action of SrFeO3−x and CeOx phases

The catalytic deep oxidation of methane over perovskite-type mixed oxide catalysts is examined. Three groups of mixed oxides (i) La1−yCeyFeO3 (0.0<y≤0.5), (ii) La1−xSrxFeO3 (0.0<x≤0.5) and (iii) La1−x−ySrxCeyFeO3 (0.0<x,y≤0.3), containing La, Sr, Ce, Fe cations in various ratios were prepared and characterized by XRD, Mössbauer spectroscopy and O2-TPD measurements. The catalysts are active in the temperature range of 440–740°C. A maximum of activity appears for y=0.3, in the series La1−yCeyFeO3 in a wide temperature range. The increase of Sr content in the series La1−xSrxFeO3 results in the enhancement of the reaction rates which is related to the presence of SrFeO3−x crystal phase that favors the surface reaction. The double substituted solids La1−x−ySrxCeyFeO3 show higher catalytic activity as compared to the activity of the two other examined perovskitic series which is related to the bifunctional synergistic action of CeO2 and SrFeO3−x crystal phases in the solids.