NO_<i>x</i>Removal over V₂O₅/WO₃–TiO₂Prepared by a Grinding Method: Influence of the Precursor on Vanadium Dispersion

Abstract

V 2 O 5 /WO 3 –TiO 2 (VWT) catalysts for selective catalytic reduction (SCR) of NO x removal were prepared by a mechanical grinding method using different vanadium precursors. The SCR performances were evaluated in simulated flue gas and explained through characterizations by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, H 2 temperature-programmed reduction, and in situ diffuse reflectance Fourier transform spectroscopy. VO(acac) 2 –VWT catalyst prepared using a vanadyl acetylacetonate (VO(acac) 2 ) precursor exhibited the highest catalytic activity and excellent resistance to SO 2 and H 2 O poisoning in 200–400 °C compared to the catalysts obtained using other precursors. The VO(acac) 2 precursor could enrich V on the surface remarkably and promote the formation and dispersion of polymeric vanadia species. Furthermore, a relatively high percentage of low-valent vanadium atoms were found on the VO(acac) 2 –VWT surface, facilitating electron transfer between V 4+ and V 5+ . Surface-adsorbed NH 3 species on VO(acac) 2 –VWT were much more reactive. The initial geometry of vanadium precursors determined the tendency of V to accumulate and further influenced the dispersion and final form of V species.