New Insight into SO Poisoning and Regeneration of CeO-WO/TiO and VO-WO/TiO Catalysts for Low-Temperature NH-SCR.

In this study, the poisoning effects of SO on the VO-WO/TiO (1%VWTi) and CeO-WO/TiO (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 NH + SO + HO + O at 200 °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 1%VWTi, NHHSO (ABS) was the main product detected after the poisoning process. Both of NHHSO and cerium sulfate species were formed on the poisoned 5%CeWTi catalyst, indicating that SO reacted with Ce/Ce, even in the presence of high concentration of NH. The decrease of BET specific surface area, NO 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 °C, but not for the 5%CeWTi catalyst. For industrial application, it is suggested that the regeneration process can be utilized for 1%VWTi catalysts after a period of time after NHHSO accumulated on the catalysts.