Thermal Stability and Catalytic Activity of the MnOx–CeO2 and the MnOx–ZrO2–CeO2 Highly Dispersed Materials in the Carbon Monoxide Oxidation Reaction

Highly dispersed MnO x –CeO 2 and MnO x –ZrO 2 –CeO 2 catalysts for the carbon monoxide oxidation reaction are synthesized. Using the XRF and the XRD methods, the formation of the Mn–Ce–O and the Mn–Zr–Ce–O solid solutions, as well as the presence of Mn 2 O 3 and Mn 3 O 4 , is established. The specific surface area of the synthesized materials is 121 and 155 m 2 /g, respectively, the particle size being equal to 8–10 nm. The X-ray photoelectron (XPS) spectra is deconvolved and the relative content of the ionic forms of Mn, the lattice oxygen O α , and the high-energy forms O β are determined. Upon studying the thermal stability of catalysts, it is established that the two-component systems have low thermal stability, causing the particle size to increase to 32 nm, the specific surface area to decrease to 29 m 2 /g, and thus the catalytic activity to deteriorate. For MnO x –ZrO 2 –CeO 2 , less significant changes take place: the particle size is 27 nm, the specific surface area is 43 m 2 /g, and thus its catalytic activity is higher than that for MnO x –CeO 2 . Investigation of the state of the components of the near-surface layer of catalysts after isothermal aging makes it possible to ascertain the change in content of ionic forms of Mn, O α , and O β . It is concluded that doping of the two-component MnO x –CeO 2 systems with the Zr 4+ ions is expedient. The resulting ZrO 2 –MnO x –CeO 2 solid solution is more resistant to high temperatures.