New Insight Into The Promotion Effect Of Cu Doped V₂O₅/WO₃-TiO₂ For Low Temperature NH₃-SCR Performance

Nitrogen oxides（NO_x）, are one of the most dangerous air pollutants that cause acid rain and photochemical smog, as well as directly do harm to human health. The selective reduction of NO_x by NH₃ is one of the most efficient NO_x emission control technologies. V₂O₅-WO₃/TiO₂ has been a well-known NH₃-SCR catalyst and shows optimum performance within a narrow temperature window of 300-400?C and the high resistance to SO₂ poisoning. Under the condition of low-load operation, the temperature of exhausted gas cannot reach to the lowest operation temperature, causing the SCR denitrification system not operation. Hence, it is urgent to develop a novel NH₃-SCR catalyst with excellent NO_x conversion at low temperature to avoid the problems associated with the existing commercial system, especially for the coal power plant. The V/WTi was first prepared by traditional incipient wetness impregnation method, and then, Cu was added to gain the V（Cu）/WTi catalyst with the same method. The promoting effect of Cu on the SCR active was evaluated and the structure-performance correlation on NH₃-SCR performance was investigated. Meanwhile, a mechanism of NH₃-SCR over V（Cu）/WTi catalyst at low temperature is proposed to further understand the promotion effect.The promotion effect of Cu on V/WTi catalyst for the selective catalytic reduction of NO_x by NH₃ was investigated in the temperature range of 150-400 ?C. The Cu addition shows a superior NH₃-SCR performance in comparison with V/WTi sample. The catalysts were characterized by XRD, Raman, EPR, H₂-TPR, XPS, and in situ DRIFTS techniques. Obtained results reveal the Cu oxides in close proximity to V oxides on the surface facilitates the formation of double redox couples of V⁵⁺/V⁴⁺ and Cu²⁺/Cu⁺, which may play a critical role in the superior NH₃-SCR performance. The electronic interactions caused by the redox cycle of Cu²⁺+V⁴⁺? V⁵⁺+Cu⁺ could significantly improve the redox properties of vanadium species, which is beneficial for the activation of NH₃ species bound to vanadium species. Moreover, the redox cycle of Cu²⁺+V⁴⁺?V⁵⁺+Cu⁺ induces the formation of high-activity nitrates species adsorbed on Cu species. The kinetic analysis reveals that the Cu doping induces the decrease of activation energy（Ea） of NH₃-SCR.