Promoting SO2 Resistance of a CeO2(5)-WO3(9)/TiO2 Catalyst for Hg0 Oxidation via Adjusting the Basicity and Acidity Sites Using a CuO Doping Method

The competition between SO2 and elemental mercury (Hg0) for active sites was an important factor for suppressing the Hg0 oxidation properties of catalysts. There were obvious differences in properties of basicity and acidity between SO2 and Hg0. Raising the SO2 resistance via adjusting the basicity and acidity sites of catalysts was promising for reducing the competition between SO2 and Hg0. This study aimed to form multiple active sites with different basicities via Cu, Fe, Mn, and Sn doping. The results indicated that Cu doping had the best modification performance. Five percent CuO doping could significantly improve the SO2 resistance of CuO(5)-CeO2(5)-WO3(9)/TiO2 and increase the mercury oxidation efficiency (MOE) from 54.7 to 85.5% in the condition (6% O2, 100 ppm NO, 100 ppm NH3, and 100 ppm SO2). CO2 temperature-programmed desorption analysis showed that CuO(5)-CeO2(5)-WO3(9)/TiO2 exhibited weak basic sites (CeO2), medium-strong basic sites (Cu-O-Ce), and strong basic sites (CuO). Therefore, the CuO in the Ce-O-Cu structure was prioritized for the reaction with acid gas SO2 and protected CeO2 from SO2 poisoning. This study prepared a highly SO2-resistant catalyst for Hg0 oxidation. This research and development will be conducive for use in Hg0 oxidation in actual coal-fired flue gases.