Significance of RuO2 Modified SCR Catalyst for Elemental Mercury Oxidation in Coal-fired Flue Gas

Catalytic conversion of elemental mercury (Hg-0) to its oxidized form has been considered as an effective way to enhance mercury removal from coal-fired power plants. In order to make good use of the existing selective catalytic reduction of NOx (SCR) catalysts as a cobenefit of Hg-0 conversion at lower level HCl in flue gas, various catalysts supported on titanium dioxide (TiO2) and commercial SCR catalysts were investigated at various cases. Among the tested catalysts, ruthenium oxides (RuO2) not only showed rather high catalytic activity on Hg-0 oxidation by itself, but also appeared to be well cooperative with the commercial SCR catalyst for Hg-0 conversion. In addition, the modified SCR catalyst with RuO2 displayed an excellent tolerance to SO2 and ammonia without any distinct negative effects on NOx reduction and SO2 conversion. The demanded HCl concentration for Hg-0 oxidation can be reduced dramatically, and Hg-0 oxidation efficiency over RuO2 doped SCR catalyst was over 90% even at about 5 ppm HCl in the simulated gases. Ru modified SCR catalyst shows a promising prospect for the cobenefit of mercury emission control.