Enhanced Durability of Monolithic V₂O₅–WO₃/TiO₂ Catalysts Prepared by a Novel One-Pot Method for the Selective Catalytic Reduction of NO_x with NH₃

Abstract

In the present work, V₂O₅–WO₃/TiO₂ (VWT) catalysts were loaded onto a cordierite monolith through a novel one-pot method (OP) and a traditional incipient wetness impregnation method (IW). The catalysts were characterized and evaluated for NH₃-SCR before and after hydrothermal aging at 600°C for 36 h. An analysis of catalyst activity showed that the hydrothermal stability of OP was much higher than that of IW. N₂-sorption and X-ray diffraction (XRD) results suggested that there were no significant differences in the textural and structural properties of the two catalysts before and after aging, except for the formation of a small amount of WO₃ crystallites on the surface of aged OP. Separate NH₃-oxidation tests revealed that the NO selectivity of aged OP was significantly lower than that of aged IW, which resulted in a much higher NO_x conversion at high temperatures during NH₃-SCR. X-ray photoelectron spectroscopy (XPS), H₂-temperature programmed reduction (H₂-TPR), and Raman spectroscopy indicated that V and W species were more stable on the surface of OP during aging rather than IW, thus inhibiting the aggregation of surface-active species and leading to a better hydrothermal stability. Furthermore, OP exhibited better adhesion of the washcoat when compared to IW and this VWT catalyst exhibited a good tolerance for SO₂.