Influence of cobalt precursor and fuels on the performance of combustion synthesized Co3O4/γ-Al2O3 catalysts for total oxidation of methane

A series of nanosized Co3O4/gamma-Al2O3 catalysts have been prepared using a combination of wetness impregnation and subsequent combustion synthesis (CS) in self-propagating mode. Alumina impregnated with various cobalt precursors and fuels, and respective as-burnt combustion-synthesized catalysts were characterised by TGA-DTA, IR-spectroscopy, N-2 adsorption-lesorption, XRD, SEM/EDX and TEM, and tested in the total oxidation of methane. The observed influence of the initial precursors cobalt acetate, mixtures of cobalt acetate/cobalt nitrate, and mixtures of cobalt nitrate wit fuels such as urea, citric acid, glycine, and glycerine on the catalytic performance correlates well with their combustion behaviour. Catalysts obtained with the combustion method at the highest velocities and the lowest temperatures during the synthesis were found to have the highest activity (complete conversion of methane at 400-425 degrees C). After two days of catalytic performance in the reaction, no considerable deactivation of combustion-synthesized catalysts was observed and their particle size remained about twice less in comparison with the sample prepared by cobalt nitrate thermal decomposition. (C) 2007 Elsevier B.V. All rights reserved.