Promotional effect and mechanism of Ce-modified V2O5-WO3/TiO2 catalyst in low-temperature NH3-SCR.

Abstract

The enhancement effect of Ce modification on V₂O₅-WO₃/TiO₂ catalysts at low temperatures was investigated for the selective catalytic reduction (SCR) of NO_x with NH₃ (NH₃-SCR). By adding 9% CeO₂ to 0.5%V₂O₅-3%WO₃/TiO₂ catalyst, the low-temperature denitrification performance of Ce₉V_0.5W₃Ti catalyst after Ce modification was significantly improved, achieving a NO conversion above 90% within a broad temperature range of 200-350℃, with catalytic activity comparable to that of 3% V₂O₅-3% WO₃/TiO₂. The catalysts were characterized by XPS, H₂-TPR, NH₃, and NO-TPD. The results indicated that the Ce additive could enhance the adsorption of NO_x on Ce₉V_0.5W₃Ti catalyst due to the synergetic interaction among the Ce and V, W species. The interaction between V and Ce also promoted the formation of V⁵⁺ and Ce³⁺ on the surface of the catalyst, which was conducive to enhancing the adsorption and oxidation capacity of the catalyst for NO. Additionally, the introduction of Ce led to a substantial deposition of nitrate species on the surface of the catalyst, especially the increase of nitrite species, which was beneficial to the NH₃-SCR reaction process, resulting in a significant enhancement of the catalyst's low-temperature catalytic activity.