XANES study of elemental mercury oxidation over RuO2/TiO2 and selective catalytic reduction catalysts for mercury emissions control

Linear combination fitting of the X-ray Absorption Near Edge Spectroscopy (XANES) was used to quantify oxidized mercury species over RuO2/TiO2 and Selective Catalytic Reduction (SCR) catalysts under different simulated flue gas conditions. Halogen gases play a major role in mercury oxidation. In the absence of halogen gas, elemental mercury can react with sulfur that is contained in both the RuO2/TiO2 and SCR catalysts to form HgS and HgSO4. In the presence of HCl or HBr gas, HgCl2 or HgBr2 is the main oxidized mercury species. When both HCl and HBr gases are present, HgBr2 is the preferred oxidation product and no HgCl2 can be found. The formation of HgO and HgS cannot be neglected with or without halogen gas. Other simulated flue gas components such as NO, NH3, SO2 and CO2 do not have significant effect on oxidized mercury speciation when halogen gas is present.