Cobalt and cobalt-iron spinel oxides as bulk and silica supported catalysts in the ethanol combustion reaction

Cobalt and mixed iron-cobalt spinel oxides Co_xFe_(3-x)O₄ supported on SiO₂ ‘IMP-Co_x-500′ and their bulk analogues ‘CP-Co_x-500′ were prepared via impregnation and co-precipitation methods respectively and calcined at 500 °C. Thermogravimetric analysis ‘ATG/DTG’, X-ray Diffraction method ‘XRD’, Texture measurements ‘BET/BJH’ and Temperature Programmed Reduction technique ‘TPR’ were used for their characterization. Their catalytic behavior in ethanol combustion was investigated. Results showed that nanostructured oxide materials with spinel structure were obtained with a good dispersion of the active phase at the surface of silica in the case of IMP-Co_x-500 compounds. The reduction behavior of the prepared samples is highly dependent on the oxide composition and interaction with the support; which is directly related to the catalytic behavior. The use of supported catalysts improves the catalytic performance and leads the reaction towards a total oxidation by decreasing greatly the formation of partial oxidation products. The obtained values of activation energies are relatively low in comparison with the literature data. A compensation effect was found by carrying out ethanol combustion through the spinel systems considered in this work.