New Insight into SO2 Poisoning and Regeneration of CeO2-WO3/TiO2 and V2O5-WO3/TiO2 Catalysts for Low-Temperature NH3-SCR

In this study, the poisoning effects of SO22 on the VO5s-O-0/TTO02 (l%VWTi) and CO(0)2-O-03/TO02 (5% CeWTi) selective catalytic reduction (SCR) catalysts were investigated in the presence of steam, and also the regeneration of deactivated catalysts was studied. After pretreating the catalysts in a flow of N-H3 + O-02 + (H)O0 +O-02 at 200 degrees C for 24 h, it was observed that the low-temperature SCR (LT-SCR) activity decreased significantly over the 1%VWTi and 5% CeWTi catalysts. For l%VWTi, N(H)4HO(44) (ABS) was the main product detected after the poisoning process. Both of N(H)4HO(04) and cerium sulfate species were formed on the poisoned 5%CeWTi catalyst, indicating that SO2 reacted with Ce3+/Ce4+, even in the presence of high concentration of NH3. The decrease of BET specific sufrace area, NOx adsorption capacity, the ratio of chemisorbed oxygen, and reducibility were responsible for the irreversible deactivation of the poisoned 5%CeWTi catalyst. Meanwhile, the LT-SCR activity could be recovered over the poisoned 1%VWTi after regeneration at 400 degrees C, but not for the 5%CeWTi catalyst. For industrial application, it is suggested that the regeneration process can be utilized for l%VWTi catalysts after a period of time after N(H)4HO(04) accumulated on the catalysts.