Effects of properties of manganese oxide-impregnated catalysts and flue gas condition on multipollutant control of Hg0 and NO

This research investigated the effects of manganese oxide (MnOx) impregnation on the physical/chemical properties and multi pollutant control effectiveness of Hg0 and NO using a V2O5-WO3/TiO2-SiO2 selective catalytic reduction (SCR) catalyst. Raw and MnOx-treated SCR samples were bean-shaped nanoparticles with sizes within 10-30 nm. Impregnating MnOx of ≤5 wt% caused limited changes in physical properties of the catalyst. The decrease in surface area when the impregnated MnOx amount was 10 wt% may stem from the pore blockage and particle growth or aggregation of the catalyst. Mn4+ was the main valence state of impregnated MnOx. Apparent crystallinity of MnOx was not observed based on X-ray diffraction. MnOx impregnation enhanced the Hg0 oxidation and NO/SO2 removal of SCR catalyst. The 5 and 10% MnOx-impregnated samples had the greatest multi pollutant control potentials for Hg0 oxidation and NO removal; however, the increasing SO2 removal that may be mainly due to SO2-SO3 conversion should be cautioned. HCl and O2 greatly promoted Hg0 oxidation. SO2 enhanced Hg0 oxidation at ≤200 ppm while NO and NH3 consistently inhibited Hg0 oxidation. Elevating flue gas temperature enhanced Hg0 oxidation. Overall, MnOx-impregnated catalysts show stable and consistent multi pollutant removal effectiveness under the test conditions.