Thermal stability of Si-doped V2O5/WO3–TiO2 for selective catalytic reduction of NOx by NH3

Abstract

The selective catalytic reduction of NOx with NH3 (NH3-SCR) is a very effective technology to control the emission of NOx, and the thermal stability of NH3-SCR catalyst is very important for removal of NOx from diesel engines. In this work, V2O5/WO3–TiO2 (VWT) and SiO2-doped V2O5/WO3–TiO2 (VWTSi10) catalysts were prepared by impregnation method and characterized by Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Raman, temperature programmed reduction by hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption by ammonia (NH3-TPD). The doping of SiO2 promotes the thermal stability of V2O5/WO3–TiO2 for NH3-SCR significantly. After calcination at 650 °C for 50 h, the operation window of 10% SiO2-doped V2O5/WO3–TiO2 is 220–480 °C, while the maximum NOx conversion on V2O5/WO3–TiO2 is about 77%. The presence of SiO2 obviously blocks the transformation of TiO2 from anatase to rutile and stabilizes the dispersion of VOx and WO3 on the surface. It is available for the existence of V4+ and the amount of surface acid sites increases, which inhabits the NH3 oxidation at the high temperature range and promotes NH3-SCR activity.