Role of flue gas components in Hg0 oxidation over La0.8Ce0.2MnO3 perovskite catalyst in coal combustion flue gas

Abstract

La0.8Ce0.2MnO3 perovskite catalyst was employed for elemental mercury (Hg0) oxidation in coal combustion flue gas. The effects of flue gas components, including O2, NO, SO2, HCl, H2O as well as the selective catalytic reduction (SCR) reductant (NH3), on Hg0 oxidation were investigated systematically. Above 90% Hg0 oxidation was obtained at 200 °C under simulated flue gas (SFG) and SCR atmosphere with a gas hourly space velocity of 60,000 h−1. Gaseous O2 regenerated and replenished surface oxygen, hence promoting the oxidation of Hg0. NO promoted the Hg0 oxidation because of the formation of active surface species like NO2. HCl facilitated the Hg0 oxidation, and 98.8% Hg0 oxidation was obtained under the atmosphere containing 10 ppm HCl in the co-presence of O2. SO2 inhibited Hg0 oxidation because of the irreversible damage on catalytic activity by reacting with the active species on the catalyst·H2O also inhibited Hg0 oxidation due to the change of catalyst surface chemistry as well as the consumption of active surface chlorine species (Cl∗). NH3 competed active sites with Hg0 and induced oxidized mercury reduction, hence limiting the Hg0 conversion. However, the inhibitive effect of NH3 could be partly offset by the promotional effect of NO. This work clarified the effects of flue gas compositions on Hg0 oxidation over a novel La0.8Ce0.2MnO3 perovskite catalyst, which is essential for further improving the catalyst activity.