Cobalt-Containing Oxide Catalysts Obtained by The Sol-Gel Method with Auto-Combustion in The Reaction of Low-Temperature Oxidation of Carbon Monoxide

Abstract

The reaction of low-temperature oxidation of carbon monoxide is important in the context of air purification and reduction of automotive emissions. Along with the search for active catalytic systems for carbon monoxide oxidation, the development of new energy-saving methods of catalyst synthesis also seems important. Cobalt-iron, cobalt-manganese, cobalt-chromium, cobalt-copper binary and cobalt-manganese-iron, cobalt-copper-iron-containing triple oxide systems for low-temperature oxidation of carbon monoxide into carbon dioxide were synthesized by the sol-gel method with auto-combustion. The samples were analyzed by X-ray diffraction, IR spectral and derivatographic methods of analysis, their specific surface area was measured by the BET method, micro-photographs were taken on a scanning electron microscope. It was established that the resulting binary and ternary cobalt-containing oxide systems are multiphase systems containing ferrites, manganites, and oxides of cobalt, copper, manganese, and iron. The resulting catalysts are active in the low-temperature oxidation of carbon monoxide at 145-180 °C. The activation energy of the CO oxidation reaction on the analyzed oxide systems was revealed by the Arrhenius equation is placed in the range of 17-33 kJ/mol. In the systems, an intensifying effect of the influence of its components on the catalytic activity is observed in the oxide and spinel phases. The Co-Cr=2:1 system, which, along with chromite, also contains cobalt oxide, which is active at a much lower temperature – 145 °C than systems with a Co-Cr=1:1 and 1:2 ratios. A similar dependence was obtained in the Co-Fe=2:1 system, i.e. in a sample that, along with cobalt ferrite, also contains cobalt oxide. On this catalyst, 100% conversion of CO to CO2 occurs at a temperature of 200 °C, and a Co-Fe = 1:2 sample with a stoichiometric ratio of metals, in which the ferritization reaction completely occurs, as experiments have shown, is active only at temperatures above 300 °C. The intensifying effect of the influence of the components on its activity is also observed in three-component systems, in which the complete conversion of CO occurs at a temperature of 145-160 °C. The appearance of various structural defects during short-term combustion of the gel without additional heat treatment, which can potentially be considered as catalytically active centers, on the one hand, and the presence of oxide and spinel phases in the composition of catalysts, which exhibit a mutual reinforcing effect, on the other hand, is demonstrative advantage of this method for the synthesis of active catalysts for low-temperature oxidation of carbon monoxide to dioxide.