Multipollutant control of Hg/SO2/NO from coal-combustion flue gases using transition metal oxide-impregnated SCR catalysts

Abstract

This research investigated the effects of transition metal oxide impregnation on the physical/chemical properties and the multipollutant (i.e., Hg/SO2/NO) control of a V2O5-WO3/TiO2-SiO2 selective catalytic reduction (SCR) catalyst. Additional V, Mn, and Cu of 5wt% as their precursor metal hydroxides were impregnated onto the catalyst surface. The impregnated metal oxides presenting in nanoscales caused an increase in total surface area of catalysts. SEM images suggested that the raw and treated catalysts presenting as bean-shaped nanoparticles within 10–30nm. V4+/V5+, Mn4+, and Cu2+ were the major valence states presenting on the surface of VOx-, MnOx-, and CuOx-impregnated catalysts, respectively. Hg0 oxidation, SO2 removal, and NO reduction of the SCR catalyst can be enhanced after the metal oxide impregnation. VOx- and CuOx-impregnated catalysts had not only excellent Hg0 oxidation but also great NO reduction. However, the increase in SO2 removal after metal oxide impregnation, assumed to be partly caused from enhancing SO2–SO3 conversion, may be of concern considering the potential downstream corrosion. Langmuir–Hinshelwood model can successfully explain the Hg0 oxidation by VOx- and MnOx-impregnated catalysts. Overall, multipollutant emission control using surface-impregnated SCR catalysts can be practically applied at 350°C under the tested coal-combustion flue gas condition.