Effect of manganese and/or ceria loading on V2O5–MoO3/TiO2 NH3 selective catalytic reduction catalyst

Abstract

The effect of manganese and/or ceria loading of V2O5–MoO3/TiO2 catalysts was investigated for selective catalytic reduction (SCR) of NOx by NH3. The manganese and/or ceria loaded V2O5–MoO3/TiO2 catalysts were prepared by the wetness impregnation method. The physicochemical characteristics of the catalysts were thoroughly characterized. The catalytic performance of 1.5 wt% V2O5–3 wt% MoO3/TiO2 (V1.5Mo3/Ti) is greatly enhanced by addition of 2.5 wt% MnOx and 3.0 wt% CeO2 (V1.5Mo3Mn2.5Ce3/Ti) below 450 °C. Compared with the V1.5Mo3/Ti catalyst with NOx conversion of 75% at 275 °C, V1.5Mo3Mn2.5Ce3/Ti exhibits higher NOx conversion of 84% with good resistance to SO2 and H2O at a gas hourly space velocity value of 150000 h−1. The active manganese, cerium, molybdenum, and vanadium oxide species are highly dispersed on the catalyst surface and some synergistic effects exist among these species. Addition of MnOx significantly enhances the redox ability of the cerium, vanadium, and molybdenum species. Addition of Ce increases the acidity of the catalyst. More active oxygen species, including surface chemisorbed oxygen, form with addition of Mn and/or Ce. Because of the synergistic effects, appropriate proportions of manganese in different valence states exist in the catalysts. In summary, the good redox ability and the strong acidity contribute to the high NH3-SCR activity and N2 selectivity of the V1.5Mo3Mn2.5Ce3/Ti catalyst in a wide temperature range. And the V1.5Mo3Mn2.5Ce3/Ti catalyst shows good resistance to H2O and SO2 in long-time catalytic testing, which can be ascribed to the highly sulfated species adsorbed on the catalyst.