Enhancement of Elemental Mercury Oxidation by Core–Shell CuCo2O4@SiO2Oxygen Carrier with Strong Oxygen Release and Weak Adsorption Capacity in Chemical-Looping Combustion

Oxygen carriers transfer lattice oxygen and oxidize elemental mercury in chemical-looping combustion (CLC). This study aims to design a core–shell CuCo2O4@SiO2oxygen carrier to enhance the removal of mercury during CLC. CuCo2O4@SiO2was prapered by combining a salt-assisted combustion method and an impregnation method. The SiO2:CuCo2O4ratio was optimized to achieve a high mercury removal efficiency. Over 10 cycles, CuCo2O4@SiO2oxygen carriers have a stable oxygen release. At 900 °C, in comparison with CuCo2O4, mercury removal efficiency over CuCo2O4@SiO2through oxidation increased from 63.46 to 82.21%. The mercury removal over CuCo2O4@SiO2through chemical adsorption decreased accordingly. This indicated that CuCo2O4@SiO2oxygen carriers promoted the oxidation efficiency of Hg0and reduced the adsorption of mercury on its surface. The DFT calculations revealed that SiO2loading over CuCo2O4surface provided part of the lattice oxygen to supplement the oxygen vacancies on the CuCo2O4surface, promoting the oxygen release from the oxygen carrier. However, the loading of SiO2inhibited the formation of surrounding oxygen vacancies to a certain extent, and the right amount of SiO2improved the oxygen release rate. Therefore, CuCo2O4@SiO2is a suitable oxygen carrier that can be applied in CLC.