Mn doped CeO₂-MoO₃/γ-Al₂O₃ catalysts for the enhanced adsorption and catalytic oxidation of Hg⁰ in oxygen atmosphere

A series of Mn-doped CeO₂-MoO₃/γ-Al₂O₃ catalysts were synthesized for the adsorption and catalytic oxidation of Hg⁰ from coal-fired flue gas using oxygen as the oxidizing agent. The results showed that the addition of Mn significantly promoted the adsorption and catalytic performances of CeO₂-MoO₃/γ-Al₂O₃ catalysts. The 6 wt% Mn-doped catalysts exhibited the best Hg⁰ catalytic oxidation efficiency of 86%. The catalysts were characterized to illustrate the structure-activity relationship of Mn-doped catalysts. It is found that the addition of Mn to the CeO₂ and MoO₃ lattice increases the concentration of oxygen vacancies on the catalyst surface which promotes the catalytic oxidation of mercury. HRTEM results indicate that the incorporation of Mn cracked CeO₂ crystal plane with an angle of 105° and may generate more active sites at the interface. Besides, the in-situ DRIFT spectra show that the acidic sites on the Mn-doped catalyst surface were dominated by Brønsted acid sites at lower temperatures which play an essential role in the adsorption of mercury. Overall, This research reveals the effect of Mn additives on the promotion of adsorption capacity and catalytic oxidation efficiency of Hg⁰, providing a promising approach to widen the effective temperature window of the catalyst.