Simultaneous NO Removal and Hg⁰ Oxidation over CuO Doped V₂O₅‑WO₃/TiO₂ Catalysts in Simulated Coal-Fired Flue Gas

Abstract

A series of CuO doped V₂O₅-WO₃/TiO₂ based commercial selective catalytic reduction (SCR) catalysts were synthesized via the improved impregnation method for simultaneous NO removal and Hg⁰ oxidation under simulated coal-fired flue gas at a temperature range of 150–400 °C. Several characterization techniques, including Brunauer–Emmett–Teller analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed reduction of H₂ (H₂-TPR), were used to characterize the catalysts. The results indicated that Cu₃-SCR catalyst exhibited the superior catalytic activity and a wide active temperature window for simultaneous NO removal and Hg⁰ oxidation. The effects of flue gas components on the catalytic activity were also investigated. The results indicated that Cu₃-SCR catalyst showed good performances on SO₂ tolerance and H₂O resistance. The effect of Hg⁰ on NO removal was almost negligible. However, the copresence of NO and NH₃ obviously inhibited the Hg⁰ oxidation activity. Further study revealed that this inhibiting effect was weakened as the consumption of NH₃. The BET and XRD results suggested that the highly dispersed Cu species was beneficial to the superior catalytic activity of the Cu₃-SCR catalyst. The XPS and H₂-TPR analyses indicated that the Cu₃-SCR catalyst possessed abundant chemisorbed oxygen and good redox ability, which was ascribed to the strong synergy between CuO and V₂O₅ on the catalyst. The redox cycle of V⁴⁺ + Cu²⁺ ↔ V⁵⁺ + Cu⁺ in Cu₃-SCR catalyst significantly improved the catalytic activity for simultaneous NO removal and Hg⁰ oxidation. The mechanism of Hg⁰ oxidation over the Cu₃-SCR catalyst was also investigated