Promotional effect of Fe and Ce co-doping on a V2O5–WO3/TiO2 catalyst for SCR of NOx with high K and Pb resistance

Abstract

There is an increasing demand to develop efficient SCR deNO_x catalysts with high resistance to alkali and heavy metals. In this study, a V₂O₅–WO₃/TiO₂ (denoted VWTi) catalyst modified with FeO_x and CeO_x in 0.05Fe/V and 1.5Ce/V molar ratio (denoted FeCeVWTi) showed enhanced SCR activity and resistance to K–Pb co-poisoning in the temperature range of 300–400 °C. The FeCeVWTi catalyst also presented outstanding tolerance to H₂O and SO₂. After K–Pb poisoning, the FeCeVWTi catalyst showed 92.7% NO_x conversion at 350 °C, much higher than that of the VWTi catalyst (70.6%). The Fe and Ce co-doping significantly improved the redox ability, V⁵⁺ ratio and surface chemisorbed oxygen ratio of the VWTi catalyst by the interaction between Fe, Ce and V. The cooperation between Fe and Ce slightly decreased the surface acidity but significantly enhanced the NO_x adsorption on the FeCeVWTi catalyst. Additionally, in situ DRIFTS revealed that the SCR reaction on VWTi followed an E–R mechanism, while Fe and Ce co-doping changed the reaction route and made the SCR reaction on FeCeVWTi follow both an E–R mechanism and an L–H mechanism. The enhanced redox ability and adsorption of NO_x played decisive roles in improving the alkali–heavy metal resistance of the FeCeVWTi catalyst.