Abstract
The Mn-Ce oxide catalysts active in the oxidation of CO were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transition electron microscopy (TEM), energy dispersive X-Ray (EDX), and a differential dissolution technique. The Mn-Ce catalysts were prepared by thermal decomposition of oxalates by varying the Mn:Ce ratio. The nanocrystalline oxides with a fluorite structure and particle sizes of 4–6 nm were formed. The introduction of manganese led to a reduction of the oxide particle size, a decrease in the surface area, and the formation of a MnyCe1−yO2−δ solid solution. An increase in the manganese content resulted in the formation of manganese oxides such as Mn2O3, Mn3O4, and Mn5O8. The catalytic activity as a function of the manganese content had a volcano-like shape. The best catalytic performance was exhibited by the catalyst containing ca. 50 at.% Mn due to the high specific surface area, the formation of the solid solution, and the maximum content of the solid solution.
Highlights
The combustion of fossil fuels in power plants, motor vehicles, and other industries emits different toxic pollutants such as CO, NOx, and volatile organic compounds (VOCs), which are very dangerous for the environment and human health
As our MnxCe1-x samples are composed of different phases, we find a catalysts contain crystalline oxides such as Mn2 O3, Mn5 O8, and Mn3 O4 and ceria
The structure, microstructure, redox and surface properties were studied by X-ray diffraction, high-resolution transmission electron microscopy with energy dispersive X-ray analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy and the differential dissolution technique
Summary
The combustion of fossil fuels in power plants, motor vehicles, and other industries emits different toxic pollutants such as CO, NOx , and volatile organic compounds (VOCs), which are very dangerous for the environment and human health. Emissions of carbon monoxide pose a serious threat to human health and ecology. The elimination of CO via catalytic oxidation is one of the most effective methods for the purification of exhaust gases from automobiles and industry [1,2]. For these purposes, manganesecontaining catalysts have received considerable attention [3,4]. The catalytic activity in oxidation reactions on manganese oxides is associated with their structural flexibility and variability of the oxidation state of manganese [3]
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