The Study of Thermal Stability of Mn-Zr-Ce, Mn-Ce and Mn-Zr Oxide Catalysts for CO Oxidation

MnO(x)-CeO(2), MnO(x)-ZrO(2), MnO(x)-ZrO(2)-CeO(2) oxides with the Mn/(Zr + Ce + Mn) molar ratio of 0.3 were synthesized by coprecipitation method followed by calcination in the temperature range of 400–800 °C and characterized by XRD, N(2) adsorption, TPR, TEM, and EPR. The catalytic activity was tested in the CO oxidation reaction. It was found that MnO(x)-CeO(2), MnO(x)-ZrO(2)-CeO(2), MnO(x)-ZrO(2) catalysts, calcined at 400–500 °C, 650–700 °C and 500–650 °C, respectively, show the highest catalytic activity in the reaction of CO oxidation. According to XRD and TEM results, thermal stability of catalysts is determined by the temperature of decomposition of the solid solution Mn(x)(Ce,Zr)(1−x)O(2). The TPR-H(2) and EPR methods showed that the high activity in CO oxidation correlates with the content of easily reduced fine MnO(x) particles in the samples and the presence of paramagnetic defects in the form of oxygen vacancies. The maximum activity for each series of catalysts is associated with the start of solid solution decomposition. Formation of active phase shifts to the high-temperature region with the addition of zirconium to the MnO(x)-CeO(2) catalyst.