Role of flue gas components in mercury oxidation over TiO2 supported MnOx-CeO2 mixed-oxide at low temperature

MnOx-CeO2 mixed-oxide supported on TiO2 (Mn-Ce/Ti) was synthesized by an ultrasound-assisted impregnation method and employed to oxidize elemental mercury (Hg-0) at 200 degrees C in simulated coal combustion flue gas. Over 90% of Hg-0 oxidation was achieved on the Mn-Ce/Ti catalyst at 200 degrees C under simulated flue gas representing those from burning low-rank coals with a high gas hourly space velocity of 60,000 h(-1). Gas-phase O-2 regenerated the lattice oxygen and replenished the chemisorbed oxygen, which facilitated Hg-0 oxidation. HCl was the most effective flue gas component responsible for Hg-0 oxidation. 10 ppm HCl plus 4% O-2 resulted in 100% Hg-0 oxidation under the experimental conditions. SO2 competed with Hg-0 for active sites, thus deactivating the catalyst's capability in oxidizing Hg-0. NO covered the active sites and consumed surface oxygen active for Hg-0 oxidation, hence limiting Hg-0 oxidation. Water vapor showed prohibitive effect on Hg-0 oxidation due to its competition with HCl and Hg-0 for active adsorption sites. This study provides information about the promotional or inhibitory effects of individual flue gas components on Hg-0 oxidation over a highly effective Mn-Ce/Ti catalyst. Such knowledge is of fundamental importance for industrial applications of the Mn-Ce/Ti catalyst in coal-fired power plants. (C) 2012 Elsevier B.V. All rights reserved.