Catalytic oxidation of Hg0 by MnOx-CeO2/γ-Al2O3 catalyst at low temperatures

MnOx-CeO2/gamma-Al2O3 (MnCe) selective catalytic reduction (SCR) catalysts prepared by sol-gel method were employed for low-temperature Hg-0 oxidation on a fixed-bed experimental setup. BET, XRD and XPS were used to characterize the catalysts. MnCe catalysts exhibited high Hg-0 oxidation activity at low temperatures (100-250 degrees C) under the simulated flue gas (O-2, CO2, NO, SO2, HCl, H2O and balanced with N-2). Only a small decrease in mercury oxidation was observed in the presence of 1200 ppm SO2, which proved that the addition of Ce helped resist SO2 poisoning. An enhancing effect of NO was observed due to the formation of multi-activity NO, species. The presence of HCl alone had excellent Hg-0 oxidation ability, while 10 ppm HCl plus 5% O-2 further increased Hg-0 oxidation efficiency to 100%. Hg-0 oxidation on the MnCe catalyst surface followed the Langmiur-Hinshelwood mechanism, where reactions tool place between the adsorbed active species and adsorbed Hg-0 to form Hg2+. NH3 competed with Hg-0 for active sites on the catalyst surface, hence inhibiting Hg-0 oxidation. This study shows the feasibility of a single-step process integrating low-temperature SCR and Hg-0 oxidation from the coal combustion flue gas. (C) 2013 Elsevier Ltd. All rights reserved.