Low-temperature activity and mechanism of WO3-modified CeO2-TiO2 catalyst under NH3-NO/NO2 SCR conditions

Abstract

The CeO2-TiO2 (CeTi) and CeO2/WO3-TiO2 (CeWTi) catalysts were prepared by a sol-gel precipitation method and their NH3-NO/NO2 selective catalytic reduction (SCR) performance was studied. N2O formation and effect of oxygen concentration on SCR performance over CeWTi catalyst were also investigated while varying the NO2/NOx ratio. Results indicate that fast SCR behavior of CeWTi catalyst has the best NH3-NO/NO2 SCR performance due to the catalyst reoxidation rate by NO2 higher than by O2. Compared with CeTi catalyst, CeWTi catalyst exhibits higher de-NOx performance under NH3-NO/NO2 SCR conditions. As the CeTi and CeWTi catalysts exhibit similar redox property, addition of WO3 provides more acid sites which accelerate the reaction between NH4NO3 and NO to get a superior low-temperature activity. Amount of N2O formation shows a peak at 250 °C mainly derived from NH4NO3 decomposition.