Catalytic oxidation of Hg0 by CuO–MnO2–Fe2O3/γ-Al2O3 catalyst

Abstract

CuO–MnO2–Fe2O3/γ-Al2O3 (CMFA) SCR (selective catalytic reduction) catalyst prepared by improved impregnation method was studied for gas-phase mercury oxidation in a simulated coal combustion flue gas at typical SCR temperatures. Brunauer–Emmet–Teller (BET), X-ray Diffractogram (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the catalyst. The CMFA catalyst yielded more than 70% oxidation efficiency using a simulated flue gas (O2, CO2, HCl, NO, SO2, H2O and balanced with N2). A 3-day experiment indicated that CMFA had a long service life and would be promising in industrial applications. In the presence of O2, an enhancing effect of HCl, NO and SO2 was observed. Without O2, NO still promoted Hg0 oxidation due to the formation of multi-activity NOx species. Meanwhile, SO2 had little effect on Hg0 oxidation and HCl inhibited Hg0 adsorption and subsequent oxidation. Hg0 oxidation over the CMFA catalyst might follow the Eley–Rideal mechanism, where gaseous or weakly bonded Hg0 reacted with adsorbed active species on the catalyst surface to generate Hg2+. Although NH3 would inhibit Hg0 oxidation, once NH3 was cut off, the efficiency fully recovered. This study provided a promising method for simultaneous removal of NO and Hg0 from coal-fired power plants.