Effects of doping Mn, Cu and Fe oxides on polyhedron CeO2 catalyst during NH3-SCR reaction

Background: Ceria (CeO2) was considered as one of the most promising catalysts due to its oxygen storage ca-pacity and redox property. However, the low activity of CeO2 catalyst in SCR reaction limited its further application on industrial processes.Methods: Transition metal (Mn, Cu and Fe) oxides were impregnated on nanopolyhedron CeO2 (CeO2-NP) cat-alysts to investigate the SCR performance.Significant findings: The Mn-CeO2-NP catalyst displayed the highest NOx conversion (ca. 70% conversion at 300 degrees C), followed by the Cu-CeO2-NP catalyst (ca. 65% conversion at 300 degrees C) and then the Fe-CeO2-NP catalyst (ca. 45% conversion at 300 degrees C). The results of H2-TPR showed that Mn-CeO2-NP and Cu-CeO2-NP catalysts were more efficient in reducing hydrogen at lower temperature than that of Fe-CeO2-NP catalysts. Based on XPS measurements, it was determined that the O alpha/(O alpha+O beta) ratio was Mn-CeO2-NP (ca. 65%)> Fe-CeO2-NP (ca. 59%)> Cu-CeO2-NP (ca. 55%) catalyst. It was also shown by Raman spectroscopy that the Mn-CeO2-NP catalyst had a higher concentration of oxygen vacancies than that of the Cu-CeO2-NP and Fe-CeO2-NP catalysts. Mean-while, more Bronsted acid sites, Lewis acid sites, nitrate and nitrites species were found in the Mn-CeO2-NP catalyst as seen by in situ DRIFT spectra.

Automated summary

Transition metal oxides impregnated on nanopolyhedron CeO2 catalysts showed that Mn-CeO2-NP catalyst exhibited the highest NOx conversion in SCR reaction, with higher oxygen vacancy concentration and more acid sites.