Synergistic effect of Ce doping and phosphorylation on optimizing the low temperature NH3-SCR activity of the spent V2O5-WO3/TiO2 catalyst

The reactivation and subsequent reuse of exhausted selective catalytic reduction (SCR) catalysts has significant economic and environmental advantages. Water and acid washing along with thermal regeneration are commonly used to eliminate toxic substances from the catalyst surface, while these processes often result in the undesired loss of active components. In this research, an impregnation approach was adopted to replenish the depleted active constituents of the spent V₂O₅-WO₃/TiO₂ (VW/Ti) catalyst. Experimental investigations were conducted to evaluate the influence of Ce/P doping on both the SCR activity of this rejuvenated catalyst and its resistance to the detrimental effects of SO₂/H₂O exposure. The optimal performance is achieved with the Ce/P co-doped VW/Ti catalyst, demonstrating remarkable efficiency in removing nearly 100% of NO_x across a broad range of temperatures from 150 to 450 °C. The incorporation of a proper content of Ce serves to increase the VO_x surface density from a sub-monolayer state to a monolayer state and fosters the formation of more surface oxygen vacancies. This transformation positively contributes to enhancing both the catalytic activity and the resistance to SO₂/H₂O poisoning. Further treatment with H₃PO₄, although rendering the catalyst more susceptible to H₂O, achieves a delicate balance between its surface acidity and redox capabilities. This optimized state not only enhances the catalyst's robustness but also further widens the active temperature window.

Graphical abstract