Low-temperature SCR activity and SO2 deactivation mechanism of Ce-modified V2O5–WO3/TiO2 catalyst

Abstract The promotion effect of ceria modification on the low-temperature activity of V 2 O 5 -WO 3 /TiO 2 catalyst was evaluated for the selective catalytic reduction of NO with NH 3 (NH 3 -SCR). The catalytic activity of 1 wt% V 2 O 5 -WO 3 /TiO 2 was significantly enhanced by the addition of 8 wt% ceria, which exhibited a NO x conversion above 80% in a broad temperature range 190–450 °C. This performance was comparable with 3 wt%V 2 O 5 -WO 3 /TiO 2 , indicating that the addition of ceria contributed to reducing the usage of toxic vanadia in developing low-temperature SCR catalysts. Moreover, V1CeWTi exhibited approximately 10% decrease in NO x conversion in the presence of 60 ppm SO 2 . The characterization results indicated that active components of V, W and Ce were well dispersed on TiO 2 support. The synergetic interaction between Ce and V species by forming V–O–Ce bridges enhanced the reducibility of VCeWTi catalyst and thus improved the low-temperature activity. The sulfur poisoning mechanism was also presented on a basis of the designed TPDC (temperature-programmed decomposition) and TPSR (temperature-programmed surface reaction) experiments. The deposition of (NH 4 ) 2 SO 4 on V1CeWTi catalyst was much smaller compared with that on V1Ti. On the other hand, the oxidation of SO 2 to SO 3 was significantly promoted on the CeO 2 -modified catalyst, accompanied by the formation of cerium sulfates. Therefore, the deactivation of this catalyst was mainly attributed to the vanishing of the V–Ce interaction and the sulfation of active ceria.