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

AbstractThe promotion effect of ceria modification on the low-temperature activity of V2O5-WO3/TiO2 catalyst was evaluated for the selective catalytic reduction of NO with NH3 (NH3-SCR). The catalytic activity of 1wt% V2O5-WO3/TiO2 was significantly enhanced by the addition of 8wt% ceria, which exhibited a NOx conversion above 80% in a broad temperature range 190–450°C. This performance was comparable with 3wt%V2O5-WO3/TiO2, 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 NOx conversion in the presence of 60ppm SO2. The characterization results indicated that active components of V, W and Ce were well dispersed on TiO2 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 (NH4)2SO4 on V1CeWTi catalyst was much smaller compared with that on V1Ti. On the other hand, the oxidation of SO2 to SO3 was significantly promoted on the CeO2-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