Promotional Effect of Ce-doped V₂O₅-WO₃/TiO₂ with Low Vanadium Loadings for Selective Catalytic Reduction of NO<i>_x</i> by NH₃

Abstract

The effect of the additive Ce on V2O5-WO3/TiO2 with low vanadium loadings for the selective catalytic reduction (SCR) of NOx with NH3 was investigated. The catalytic activity of 0.1% V2O5-6% WO3/TiO2 (V0.1W6Ti) was greatly enhanced by the addition of 10 wt % of Ce in the broad temperature range of 200−500 °C. The catalysts were characterized by BET, XRD, XPS, TPD, H2-TPR, and DRIFTS. The results indicated that the active components of V and W were well-dispersed, while a small cluster of cubic CeO2 appeared over the V0.1W6Ce10Ti catalyst. The Ce additive could enhance the NOx adsorption and then accelerate the SCR reaction due to the synergetic interaction among the Ce and V,W species. Ce mainly existed in the form of Ce3+ oxide in V0.1W6Ce10Ti catalysts, which was beneficial for the oxidation of NO to NO2. Moreover, the DRIFTS results showed that the Ce additive on V0.1W6Ti could provide stronger and more active Brønsted acid sites, which were beneficial for the SCR reaction. The Ce additive also enhanced the reaction rate because the ad-NH4+ disappeared quickly in the presence of NO and O2. NO2, nitrate, and nitrite species formed on the Ce-doped VWTi catalyst because NO was easily oxidized due to the addition of Ce on V0.1W6Ti.