Elemental Mercury Removal over CeO₂/TiO₂ Catalyst Prepared by Sol–Gel Method

Elemental mercury (Hg0) emitted from a coal-fired boiler is a serious menace and challenge to humans. Using high-efficiency CeO2/TiO2 catalysts to enhance the conversion from elemental mercury to oxidized mercury is a promising approach to reducing Hg0 emission. However, most of the CeO2/TiO2 catalysts were prepared by impregnation method or coprecipitation method while little attention has been paid to sol–gel method, which has many advantages in material production. In this study, a series of catalysts were synthesized through the sol–gel method to remove the gaseous Hg0 from simulated flue gas. The effect of vanadium (V) on Hg0 removal efficiency and the simultaneous removal of Hg0 and NO were also investigated. The results showed the optimal temperature for Hg0 removal over the CeO2/TiO2 catalysts was 350 °C. The oxidation of Hg0 could be promoted by O2, HCl, and NO, but inhibited by NH3 and SO2. The addition of vanadium could enhance the Hg0 removal performance and the resistance to NH3 and SO2. A synergetic effect was found during the simultaneous removal of Hg0 and NO. The high redox reaction reactivity of Ce4+/Ce3+ and V5+/V4+ should take the credit for the oxidation of Hg0 and the removal of NO. Based upon the performance tests and the characterization experiments of the samples, the detailed mechanisms of the Hg0 and NO removal over the catalysts were proposed.