Roles of Promoters in V₂O₅/TiO₂ Catalysts for Selective Catalytic Reduction of NOx with NH₃: Effect of Order of Impregnation

Recently, various promoters for commercial selective catalytic reduction (SCR) catalysts are used to improve DeNOx activity at low temperature. We aimed at finding the optimum condition to prepare V₂O₅/TiO₂ catalyst by changing promoters (W, Ce, Zr and Mn), not only for improving SCR reactivity, but also for reducing N₂O formation at high temperature. In addition, we changed the order of impregnation between promoter and vanadium precursors on TiO₂ support and observed its effect on activity and N₂O selectivity. We utilized various analytical techniques, such as N₂ adsorption–desorption, X-ray Diffraction (XRD), Raman spectroscopy, UV-visible Diffuse Reflectance Spectroscopy (UV-vis DRS) and Temperature Programmed Reduction with hydrogen (H₂-TPR) to investigate the physicochemical properties of V₂O₅/TiO₂ catalysts. It was found that W and Ce added V₂O₅/TiO₂ catalysts showed the most active DeNOx properties at low temperature. Additionally, the difference in impregnation order affected the SCR activity. The superiority of low temperature activity of the vanadium firstly added catalysts (W or Ce/V/TiO₂) is attributed to the formation of more polymerized V₂O₅ on the sample.