Catalytic properties of stoichiometric and non-stoichiometric LaFeO 3 perovskite for total oxidation of methane

Abstract

Perovskite LaFeO 3 and derived materials La (1− ϵ) FeO (3−1.5 ϵ) with ϵ=0.1, 0.2, 0.3 have been prepared as polycrystalline powders by thermal low-temperature decomposition of La and Fe nitrates, a method which ensures a high surface area. They have been used in catalytic methane combustion in the range 300–450 °C, showing a 100% selectivity to carbon dioxide. The reaction is indeed characterised by two ranges with different dependence of the reaction rate on temperature, as shown by the Arrhenius plot, whose slope decreases markedly above about 375 °C. Temperature programmed desorption experiments of oxygen allowed us to ascertain the presence of two surface oxygen species, whose desorption occurs, respectively before and after the above indicated temperature on this basis, we propose here an hypothesis on the way of working of the catalysts. The characterisation of the catalysts has been then completed by means of temperature programmed reduction, whose results contribute to strengthen the hypothesis that the catalyst reduction operated by methane involves a smaller number of lattice planes than reduction of hydrogen.