Excellent alkali resistance of Fe, Ce and sulfates co-modified V2O5–WO3/TiO2 catalyst for selective catalytic reduction of NOx with NH3

Abstract

Improving the alkali resistance of catalysts for selective catalytic reduction of NOx with NH3 is still a challenge. In this work, the co-modification with Fe, Ce and sulfates on V2O5–WO3/TiO2 catalysts (denoted as xSFeCeVWTi) significantly enhances its alkali resistance with K element as a representative. A series of xSFeCeVWTi catalysts was synthesized by wet impregnation with designed 0.05Fe/V, 1.5Ce/V and different S/V molar ratios x. The NOx conversion and K resistance of xSFeCeVWTi catalysts increase with the increase of loading amounts of sulfates but no longer further increase as the sulfates load is excessive to block the pores of catalysts and hinder the adsorption of reactants. The optimal modified catalyst in about 2.2S/V actual loading ratio, corresponding to 10.5SFeCeVWTi samples, shows over 99.0% NOx conversion and N2 selectivity at 300–400 °C after K-poisoning. The interaction between Fe, Ce and V improves its redox ability but slightly weakens surface acidity, while the proper amount of sulfate species enriches surface Brønsted acid sites but attenuates its redox capability. However, a balance of redox capacity and surface acidity, caused by Fe, Ce and sulfate co-modification, contributes to the excellent K resistance of 10.5SFeCeVWTi catalyst. Finally, the change of physicochemical properties influences the reaction mechanism which follows the Eley–Rideal mechanism on 10.5SFeCeVWTi catalyst. These results show that the co-modification with Fe, Ce and sulfates is a good way to improve the alkali tolerance of V2O5–WO3/TiO2 catalyst in industrial applications.