Boosting SO2‑tolerant oxidation of Hg0 and chlorobenzene over MnCo2O4@TiO2 catalyst via constructing shielding effects

Abstract

Currently, it was still challenging to improve the SO2-tolerant catalytic oxidation of Hg0 and chlorobenzene in flue gas. Herein, we developed a MnCo2O4@TiO2 core–shell material that employed a self-shielding mechanism to prevent sulfate deposition. The optimal MnCo2O4@TiO2-2 catalyst achieved 100 % Hg0 removal efficiency at 250 °C under 150–600 ppm SO2, and also showed enhanced SO2 resistance during chlorobenzene conversion at 275 °C. The strong interaction between MnCo2O4 and TiO2 facilitated the electronic transfer from MnCo2O4 to TiO2, thereby producing more Co3+ and maintaining the high reactivity. Further, the mesoporous TiO2 layer facilitated the generation of moderate acid sites, improved the distribution of surface oxygen species, and weakened SO2 adsorption on catalyst. Under the protection of mesoporous TiO2 layer, the generation of Mn/Co sulfates could be inhibited effectively. In particular, the suitable TiO2 shell balanced the chemical adsorption and oxidation processes of Hg0 on the catalyst. This enhancement led to improved single Hg0 removal efficiency and SO2-tolerant Hg0 removal performance. During chlorobenzene degradation in presence of SO2, the oxidation path of chlorobenzene on MnCo2O4@TiO2 occurred via chlorobenzene → phenolates → maleates → formates/acetates → CO2 and H2O. Although sulfate formation would cover the active surface and inhibit the reaction path, the TiO2 shell could attenuate this negative effect. This study provided a new approach for the development of SO2-tolerant transition metal oxide with superior performance, holding significant academic and practical value.