Insight into regeneration mechanism with sulfuric acid for arsenic poisoned commercial SCR catalyst

Abstract

Washing method by sulfuric acid was investigated in the context of deactivation and regeneration mechanism of arsenic deactivated catalyst over V2O5-WO3/TiO2 catalyst. The physical and chemical properties changes for catalysts were characterized by XRD, SEM, BET, Raman, XPS, NH3-TPD and in situ DRIFT, therein including morphology, structure, chemical states, surface acidity and functional groups. The results indicated that arsenic species mainly consisted of As2O5 on the arsenic poisoned catalyst surface. It increased N2O formation due to high active oxygen ratio of poisoned catalyst. After regeneration, the N2O formation was reduced. Arsenic oxides covering on catalyst surface could be almost wipe off with sulfuric acid. As-OH group disappeared, and the Brønsted and Lewis acid sites were re-exposed. Moreover, a new Brønsted acid sites (S-OH) was formed by chelating bidentate sulfates (SO42−) since it introduced S=O into anatase TiO2 lattice. However, some vanadium species were lost and the remaining species tended to form V4+, the activity had an apparent decrease in the temperature range of 300–400 °C.