Effect of FeOx and MnOx doping into the CeO2–V2O5/TiO2 nanocomposite on the performance and mechanism in selective catalytic reduction of NOx with NH3

Researchers have been working on the development of new low temperature catalysts with high NOx conversion, N2 selectivity and resistance to SO2 and H2O in selective catalytic reduction of NOx with NH3 at 120–300 °C. Here, a series of novel FeOx–CeO2–V2O5/TiO2 (FeCeVTi) and MnOx–CeO2–V2O5/TiO2 (MnCeVTi) catalysts were synthesized via a modified solvent-free sol–gel method and their catalytic performances at low temperature were enhanced by doping different contents of Fe or Mn. Among them, the 7%FeCeVTi catalyst (7.0% Ce/Ti and 1.0% V/Ti molar ratio) showed the optimal integrated catalytic performance, whose NOx conversion remained above 92% between 210 and 360 °C and above 86.1% when introducing SO2 for 24 h at 250 °C with nearly 100% N2 selectivity. The interaction among Fe, Ce and V species in FeCeVTi catalysts contributed to their higher Ce3+/Ce4+ and surface V5+ ratio, appropriate redox ability, and more acid sites, which may result in the improvement of their SCR activity and resistance to SO2. The addition of MnOx into the CeVTi system increased the catalytic activity below 235 °C, but largely decreased the N2 selectivity and did not enhance the resistance to SO2 and H2O, which may be due to the too high redox ability of the MnCeVTi catalyst. The NH3-SCR reaction on the CeVTi sample followed the E–R mechanism, and the coexistence of E–R and L–H mechanisms was observed on the FeCeVTi catalyst.