Synergistic catalytic oxidation of Hg0 and NH3-SCR of NO over MnCeTiOx catalyst in flue gas

Abstract

The catalytic oxidation over the selective catalytic reduction (SCR) catalysts is efficient and economical for the removal of elemental mercury (Hg0). Herein, we studied the catalytic oxidation of Hg0 over the MnCeTiOx catalysts with different Ce contents synthesized by a polyethylene glycol-assisted (PEG) co-precipitation method. By increasing the contents of Ce loaded, the oxidizability of MnCeTiOx was reduced, but the NH3-SCR performance and H2O/SO2 resistance were improved. The MnCe(0.1)TiOx catalyst presented high NO conversion rate exceeding 80% at 160–360 °C and gas space hourly velocity (GHSV) of 80, 000 h−1 and Hg0 oxidation efficiency beyond 95% at 100–300 °C and 400, 000 h−1, respectively. The surface-active oxygen including chemisorbed surface O and unsaturated-coordinated surface lattice O acted as the active sites for Hg0 oxidation. The competitive adsorption and oxidation of SO2 and NH3 could suppress the adsorption of Hg0. NO and SO2 could be oxidized into active intermediates, such as NO3-* and SO42-* , which benefited the oxidation of Hg0. However, the NH3 was a strong Lewis base and reducing agent, which could be oxidized to NH2 * or NH* and then hinder the oxidation of Hg0. These results clarified the interaction among the multi-components during the oxidation of Hg0 over the SCR catalysts, which is beneficial to the development of Hg0 treatment techniques in low-temperature flue gas.