Reduction of SO₂ into sulfur over Ce-based catalyst: Performance optimizations and reaction mechanisms

Sulfur dioxide catalytic reduction is sustainable with acceptable desulfurizing efficiency while recovering valuable solid sulfur. However, the long-term challenge lies in enhancing catalytic activity and selectivity. In this work, we constructed Ce-based catalysts with controllable metal loadings by a straightforward impregnation method. By strategically screening metal species and loading amounts, efficient conversion of SO₂ into sulfur has been achieved. Experiments show that the 15 % Gd-Ce-O_x exhibited superior catalytic activity, achieving an impressive 97 % conversion of SO₂ and 98 % selectivity towards sulfur at 400 °C. Furthermore, the reduction of SO₂ by CO over the 15 % Gd-Ce-O_x catalysts followed the L-H and E-R mechanisms. This involved the adsorption of SO₂ on the catalyst surface leading to the formation of weakly adsorbed sulfate, dinuclear bidentate sulfate, sulfite and bisulfite species, followed by the participation of CO in the reaction resulting in the generation of weakly adsorbed CO, bicarbonate, monodentate carbonate and uncoordinated CO₃^2-. Ultimately, the reaction culminates in the formation of the sulfur and CO₂. This work provides a simple and efficient method for the preparation of sulfur by controlled metal-loaded Ce-based catalysts, which effectively realizes the sulfur dioxide resourceization of industrial flue gas.