LAUSR

A series of V2O5–WO3/TiO2 catalysts treated by KCl or K2SO4 were prepared using the equal volume impregnation method. The effects of adding these K salts on SO2–SO3 conversion and on denitration behavior over the catalyst were studied, using reactor trials and various characterization methods, including NH3-TPD, H2-TPR, ICP, BET, XRD, SEM, FT-IR and XPS. The results of catalytic activity evaluation tests show that adding K salts decreases the denitration efficiency, while SO2 enhances the activity of the KCl-poisoned catalyst to an extent. The presence of K salts also improves the SO3 formation rate, such that the SO3 formation rate for the K2SO4-poisoned catalyst is as high as 1.53% at 410 °C (compared with 0.60% for the fresh catalyst). The characterization data indicate that K salts aggregate on the catalyst surface, blocking the pores of the catalyst. The reduction ability of the catalyst is decreased slightly and new weakly acidic sites appear. In addition, the concentration of strongly acidic sites declines. SO2 can increase the surface acidity of the catalyst. K salts increase the number of V5+=O bonds and weakly acidic sites, but consume oxygen atoms along with V and W species. Importantly, the strength of the V5+=O bonds, the concentration of surface chemically adsorbed oxygen and the V4+/V5+ ratio all played vital roles in improving the conversion of SO2–SO3 and in enhancing the NO reduction.Graphical Abstract