CoMnMgAl mixed oxides prepared by a microwave assisted self-combustion synthesis for toluene total oxidation

Abstract Volatile organic compounds (VOCs) are one of the most relevant air pollutants as they act as precursor agents for photochemical smog, acid rain and other noxious compounds. Catalytic oxidation stands out as an abatement method of VOCs thanks to its high efficiency and low energy requirements. Within this approach, catalysts based on cobalt and manganese are remarkable systems due to their excellent redox properties and the oxygen mobility within the mixed oxides structures. In this work, CoMnMgAl-Ox type catalysts were prepared by a microwave (MW) assisted self-combustion synthesis method varying the Co/Mn molar ratio between 0 and 1, the MW irradiation power between 80 and 500 W and the impregnation or non-impregnation with platinum at 1.0 %. The catalysts were characterized by XRD, N2 adsorption-desorption isotherms, HR-TEM and XPS techniques and evaluated in the catalytic oxidation of toluene in diluted gas phase at atmospheric pressure. All solids prepared by MW showed higher catalytic activities than their equivalents prepared by traditional self-combustion, demonstrating that the use of microwaves in the synthesis enhances the catalytic activity of materials in the oxidation due to the prevalence of Co (III) species and a smaller particle size. Additionally, it was found that the Co/Mn = 0.6 M ratio in the oxide, gives rise to the most active catalyst, presenting conversions comparable to those of the catalysts impregnated with platinum.