Mn and Fe oxides co-effect on nanopolyhedron CeO2 catalyst for NH3-SCR of NO

The active components Mn and Fe oxides were loaded on the surface of CeO₂ catalyst with nanopolyhedrons morphology (CeO₂-NPs) by impregnation method to improve the CeO₂-NPs catalyst catalytic performance. The activity test results showed that the activity order of these catalysts within the temperature of 100–300 °C was Fe-Mn-Ce > Mn-Ce > Ce catalyst, and the NO conversion rate of Fe-Mn-Ce catalyst was the highest at 200 °C, which was about 98%. The performances of these catalysts were further investigated by SEM, XRD, XPS, Raman spectra, H₂-TPR, NH₃-TPD and in situ DRIFT. The results indicated that Fe-Mn-Ce catalyst possessed the best reducibility and surface acidity of the three catalysts. According to the XPS and Raman spectra tests, the sequences of the ratio of O_α/(O_α+O_β) and Ce³⁺/(Ce³⁺+Ce⁴⁺) were both Fe-Mn-Ce > Mn-Ce > Ce catalyst, which indicated that the Fe-Mn-Ce catalyst possessed the most oxygen vacancy and further improved the catalytic activity of the catalyst. Moreover, the Fe-Mn-Ce catalyst also exhibited the best tolerance to SO₂ of the three catalysts at 225 °C. In general, simultaneous loading of manganese and iron oxides on the CeO₂-NPs catalyst could effectively improve the low temperature SCR performance of the catalyst.