Oxygen-deficient SrFeO3 - δ (0.02 < δ < 0.26) perovskites were prepared by soft-chemistry procedures, followed by annealing under different conditions, including high oxygen pressure. These materials contain Fe cations in the mixed Fe3+−Fe4+ valence state. The samples were characterized by X-ray and neutron powder diffraction, thermal analysis under reducing conditions, temperature-programmed reduction and desorption, specific surface area measurements, and XPS. The most deficient oxide, SrFeO2.74, shows a complex neutron diffraction diagram corresponding to a superstructure of perovskite in which half of the Fe cations are pentacoordinated to oxide anions in a pyramidal configuration. By contrast, the other half are octahedrally coordinated. The materials were tested as catalysts for methane oxidation. At moderate temperatures, a significantly higher catalytic activity was observed for the most oxygen-deficient sample, which is consistent with the oxygen desorption ability exhibited by this material, containing a large number of oxygen vacancies in its crystal structure.

The partial oxidation of methane to CH3OH and HCHO (C1-oxygenates) was evaluated over a low surface area V2O5/SiO2 catalyst. The introduction of low amounts of NO (0-2.92% vol) to the reaction feed strongly enhanced both the conversion of methane and selectivity to C1-oxygenates. In the presence of NO, both the reaction temperature and the CH4/O2 ratio affected selectivity to CH3OH and HCHO. Selectivity values of C1-oxygenates as high as 40% at a methane conversion close to 40% were obtained.

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