Dual-Environment Mercury Adsorption: Role of Active Oxygen Species in Cu–Mn–Ce Composite Oxides under Natural Gas and Flue Gas Conditions

Cerium-based composite oxides have been intensively investigated for the elimination of elemental mercury (Hg 0 ) from natural gas and flue gas. Because of distinct operational conditions, the required types of active oxygen species in composite oxides differ substantially between these two atmospheric environments. Nevertheless, the diversity of oxygen species has led to considerable debate regarding the active sites responsible for the Hg 0 removal. The exploration of these oxygen species is essential as it directly guides the rational design of active sites in sorbents. In this work, we designed and synthesized sorbents with different oxygen species and systematically investigated the contributions of these oxygen species in the Hg 0 removal reaction. Cu–Mn–Ce (CMC) composite oxides were successfully prepared by the coprecipitation method. Characterization results indicate that the incorporation of Cu and Mn ions into the CeO 2 lattice indeed significantly increases the concentration of oxygen vacancies and releasable lattice oxygen. The Hg 0 removal efficiencies of CMC for natural gas and flue gas can be maintained above 90.0% and 99.0%, respectively, even under a high gas hourly space velocity of 480,000 h –1 . Furthermore, CMC exhibits superior cyclic stability and high SO 2 resistance for Hg 0 removal. Combined with the results from adsorption tests and characterization, it can be concluded that the surface-active oxygen species determine the catalytic oxidation and adsorption efficiency of Hg 0 , while the releasable lattice oxygen species ensure the continuous supply of active oxygen under extremely oxygen-deficient conditions.