Significance of Fe2O3 modified SCR catalyst for gas-phase elemental mercury oxidation in coal-fired flue gas

Abstract

To improve the ability of commercial selective catalytic reduction (SCR) catalyst to catalyze the oxidation of gaseous elemental mercury, Fe2O3 was introduced. Modifying with Fe2O3 can significantly enhance the elemental mercury oxidation ability of SCR catalyst. Fe2O3/SCR prepared by an impregnation method was employed as mercury oxidation catalysts in the simulated flue gas, and the role of Fe2O3 was investigated. The temperature window was from 150 to 450°C. In this study, Fe2O3/SCR (1% Fe, wt.) was found to be an optimal catalyst with a mercury oxidation efficiency of higher than 90% at 350°C using a simulated flue gas. The catalysts were characterized by X-ray diffraction (XRD), Brunauer Emmet Teller (BET) measurements, and X-ray photoelectron spectroscopy (XPS). The results indicated that the Fe2O3 was well-dispersed on the surface of SCR. The surface areas and catalytic oxidation activity were not consistent patterns, and the diameter of the mercury atom was much smaller than the pore diameter of the Fe2O3/SCR catalysts. Loading content of Fe2O3 was a very important factor for the removal of mercury. HCl was the most effective flue gas component responsible for the Hg0 oxidation. However, SO2 had a slight inhibition effect on Hg0 oxidation. Furthermore, change experiment of a mercury valence state was performed. And the mechanism of Hg0 oxidation was also discussed.