Efficient enhancement of the anti-KCl-poisoning performance for V2O5-WO3/TiO2 catalysts by Ce(SO4)2 modification

Abstract

Alkali metal species have a severe poisoning effect on V2O5-WO3/TiO2 (VWTi) selective catalytic reduction catalysts, series of sulfate-doped VWTi catalysts were prepared in this study and their resistances to alkali metals were tested to explore a efficient solution to alleviate alkali metal poisoning. The results of activity tests showed that the Ce(SO4)2-doped catalyst possessed the best resistance ability on alkali metals, with the optimal Ce(SO4)2 loading of 7.5 ​wt%. The screened catalyst (noted as VWTi-7.5Ce) exhibited an outstanding denitrification efficiency and a perfect resistance to SO2 and H2O in the typical denitrification temperature range (250-375 ​°C) with 2.0 ​wt% KCl poisoning. Despite the fact that KCl decreased the specific surface area and the average pore size of VWTi catalyst, which weakened the redox ability and decreased the surface acidities, abundant active acid sites were provided on the surface of the VWTi-7.5Ce catalyst after the introduction of SO42−, which mitigated the toxic effects of alkali metals on the acidity of the catalyst. The introduced Ce4+/Ce3+ redox couples also enhanced the chemisorbed oxygen ratio, thus promoting the redox ability of the catalyst. Moreover, the Ce3+ species could preferentially interact with KCl over the catalyst, thus protecting the active V5+ species. Therefore, the abundant acid sites brought by SO42− and the redox ability provided by Ce4+/Ce3+ both contributed to the excellent anti alkali metal poisoning ability of the VWTi-7.5Ce catalyst.