Effect of the Calcination Temperature on the Properties of MnO_x–CuO–ZrO₂–CeO₂ Catalysts for CO Oxidation

Four-component oxide catalysts MnO_x–CuO–ZrO₂–CeO₂ are synthesized by co-precipitation with varying the calcination temperature from 400 °C to 800 °C. Formation and decomposition processes in mixed oxides are studied by X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The redox properties of the obtained samples are tested by temperature-programmed hydrogen reduction, and the catalytic characteristics are examined in the CO oxidation reaction. At 400-600 °C homogeneous solid solution Mn_xCu_yZr_zCe_qO₂ with the fluorite structure is formed. Temperature elevation to 700-800 °C facilitates the gradual decomposition of initial oxide, with manganese and copper cations leaving its composition in the form of highly dispersed CuO and Cu_xMn_3–xO₄ particles. The occurrence of different active states in the catalyst and their transitions into each other under the temperature effect is shown to maintain the high activity in the CO oxidation reaction up to 800 °C.