| Summary: | The MnO<sub>2</sub>/TiO<sub>2</sub> (TM<sub>5</sub>) catalyst modified by molybdenum was used for mercury oxidation at different temperatures in a fixed-bed reactor. The addition of molybdenum into TM<sub>5</sub> was identified as significantly enlarging the optimal temperature range for mercury oxidation. The optimal mercury oxidation temperature of TM<sub>5</sub> was only 200 °C, with an oxidation efficiency of 95%. However, the mercury oxidation efficiency of TM<sub>5</sub> was lower than 60% at other temperatures. As for MnO<sub>2</sub>−MoO<sub>3</sub>/TiO<sub>2</sub> (TM<sub>5</sub>Mo<sub>5</sub>), the mercury oxidation efficiency was above 80% at 200−350 °C. In particular at 250 °C, the mercury oxidation efficiency of TM<sub>5</sub>Mo<sub>5</sub> was over 93%. Otherwise, the gaseous O<sub>2</sub>, which could supplement the lattice oxygen in the catalytic reaction, played an important role in the process of mercury oxidation over TM<sub>5</sub>Mo<sub>5</sub>. The results of X-ray photoelectron spectroscopy (XPS) suggested that mercury oxidized by O<sub>2</sub> over TM<sub>5</sub>Mo<sub>5</sub> followed the Mars−Maessen mechanism.
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