A relationship between the V4+/V5+ ratio and the surface dispersion, surface acidity, and redox performance of V2O5–WO3/TiO2 SCR catalysts

Abstract

A series of V₂O₅–WO₃/TiO₂ catalysts with different vanadium loading amounts were prepared by an impregnation method and were characterized by XRD, Raman spectroscopy, XPS, DRIFTS, Py-DRIFTS, NH₃-TPD, H₂-TPR, etc. The results show that the catalytic activity is related to the ratio of V⁴⁺/V⁵⁺. The variation of the V⁴⁺/V⁵⁺ ratio caused by the different dispersion states of vanadia oxide leads to changes in the surface acidity and redox properties of the catalysts. As the V⁴⁺/V⁵⁺ ratio reaches the maximum value, the apparent activation energy (E_a) required to form the transition state on the Brønsted acid sites is the lowest. Artificial regulation of vanadium loading to properly increase V⁴⁺/V⁵⁺ content may affect the interactions between V, W, O and Ti atoms, which enhances NH₃-SCR reaction performance.