Simultaneous removal of NO and dioxins over V2O5-WO3/TiO2 catalyst for iron ore sintering flue gas: The poisoning effect of Pb

Abstract

V2O5-WO3/TiO2 (VWTi) catalyst is widely used for simultaneously eliminating the NO and dioxins from the iron ore sintering flue gas. However, the catalyst is confronted with deactivation by heavy metals during operation. Here, we studied the effects of PbCl2 and PbO on catalytic elimination NO and dioxins over VWTi catalyst based on the presence of lead species in sintering flue gas. Variations of catalytic activity, surface acidity, and regeneration performance were evaluated. The results confirmed that the deactivation degree was in correlation with the lead content, the influence of the existing forms of lead on the catalyst surface on denitrification, and dioxin removal activities were following the sequence: PbO > PbCl2. The introduction of lead species could occupy acidic sites on the catalyst surface, resulting in a decrease in the V5+/V4+ molar ratio, the surface chemisorbed oxygen, and the amount of acid on the catalyst surface. XRD investigations show that the formation of PbSO4 precipitates by the reaction of lead ions with sulfate groups on the catalyst's surface reduced the number of acidic sites provided by sulfate groups. Besides, the formation of PbSO4 on the catalyst's surface also led to the failure of lead ion removal by regeneration treatment, consequently resulting in the catalytic activity can handly be effectively repaired.