Effects of silica additive on the NH3-SCR activity and thermal stability of a V2O5/WO3-TiO2 catalyst

V2O5/WO3-TiO2 and V2O5/WO3-TiO2-SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750 degrees C in 10 vol% H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3-TiO(2)catalyst severely over the entire measured temperature range. Interestingly, the NH3-SCR activity of the silica-modified catalyst at 220-480 degrees C is enhanced after ageing. The catalysts were characterized by X-ray diffraction, nitrogen adsorption, X-ray fluorescence, Raman spectroscopy, H-2 temperature-programmed reduction, and NH3 temperature-programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3-TiO2 catalyst was significantly improved. (C) 2016, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved.