State of the copper ions in the catalysts for oxidation of carbon monoxide to carbon dioxide

The state of the copper ions in the catalysts for the oxidation of carbon monoxide to carbon dioxide, prepared by dissolving an activated copper-containing aluminum alloy in water followed by calcination (method A) and by impregnation of the support produced by dissolving activated aluminum in water with copper nitrate solution (method B), was investigated by diffuse reflection electronic spectroscopy. It was established that the catalysts contain Cu²⁺ ions stabilized in fields of octahedral symmetry. The concentration of these ions depends on the method of synthesis of the catalyst, its copper content, and the pretreatment temperature. It is higher in the samples produced by impregnation than in the samples produced by fusion; increase in the amount of copper leads to a decrease while increase in the calcination temperature leads to an increase in the concentration of the above-mentioned ions. Treatment of the oxide systems with the reaction mixture does not affect the state and concentration of Cu²⁺. The catalytic activity of the samples depends on the method of preparation and increases with decrease in the amount of Cu²⁺ (O_h) and with increase in the content of the CuO phase in the system.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 786–790, April, 1992.