Thermal stability and catalytic activity of highly dispersed materials MnOx – CeO2 and MnOx – ZrO2 – CeO2 in the oxidation of carbon monoxide

Abstract

Highly dispersed catalysts MnOx-CeO2 and MnOx – ZrO2 – CeO2 were synthesized for the oxidation of carbon monoxide. Using XRD and XRF methods, the formation of Mn – Ce – O and Mn – Zr – Ce – O solid solutions, as well as the presence of Mn2O3 and Mn3O4, was established. The specific surface area of the synthesized materials is 121 and 155 m2/g, respectively, with a particle size of 8-10 nm. Deconvolution of XPS spectra was carried out, the relative content of ionic forms of Mn, lattice oxygen Оα and high-energy forms Оβ was determined. When studying the thermal stability of the catalysts, it was found that bicomponent systems have low thermal stability, which leads to an enlargement of particle sizes to 32 nm, a decrease in the specific surface to 29 m2/g, and, as a consequence, to a decrease in catalytic activity. While for MnOx – ZrO2 – CeO2, less significant changes are observed: the particle size is 27 nm, the specific surface is 43 m2/g, while the catalytic activity is higher than for MnOx – CeO2. The study of the state of the components of the surface layer of the catalysts after isothermal exposure allowed to ascertain changes in the content of the ionic forms Mn, Oα, and Oβ. Based on the studies, it can be concluded that it is advisable to dope the bicomponent systems MnOx – CeO2 with Zr4+ ions. The resulting solid solution ZrO2 – MnOx – CeO2 is more stable under the influence of high temperatures.