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

Abstract

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.