Promotional Effect of Ce-doped V2O5-WO3/TiO2 with Low Vanadium Loadings for Selective Catalytic Reduction of NOx by NH3

The effect of the additive Ce on V 2 O 5 -WO 3 /TiO 2 with low vanadium loadings for the selective catalytic reduction (SCR) of NO x with NH 3 was investigated. The catalytic activity of 0.1% V 2 O 5 -6% WO 3 /TiO 2 (V 0.1 W 6 Ti) 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, H 2 -TPR, and DRIFTS. The results indicated that the active components of V and W were well-dispersed, while a small cluster of cubic CeO 2 appeared over the V 0.1 W 6 Ce 10 Ti catalyst. The Ce additive could enhance the NO x 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 Ce 3+ oxide in V 0.1 W 6 Ce 10 Ti catalysts, which was beneficial for the oxidation of NO to NO 2 . Moreover, the DRIFTS results showed that the Ce additive on V 0.1 W 6 Ti 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-NH 4 + disappeared quickly in the presence of NO and O 2 . NO 2, nitrate, and nitrite species formed on the Ce-doped VWTi catalyst because NO was easily oxidized due to the addition of Ce on V 0.1 W 6 Ti.