Catalytic reduction of sulfur dioxide with carbon monoxide over tin dioxide for direct sulfur recovery process

SO2 reduction by CO over SnO2 catalyst was studied in this work. The parameters were the reaction temperature, space velocity (GHSV) and [CO]/[SO2] molar ratio. The optimal temperature, GHSV and [CO]/[SO2] molar ratio were 550 °C, 8000 h−1 and 2.0, respectively. Under these conditions, the SO2 conversion and sulfur selectivity were about 78% and 68%, respectively. The following reaction pathway involving two mechanisms was proposed in SO2 reduction by CO over SnO2 catalyst: in the first step involving Redox mechanism, the elemental sulfur was produced by the mobility of the lattice oxygen between SO2 and SnO2 surface. In the second step, COS was formed by the side reaction between elemental sulfur and CO or metal sulfide and CO. In the third step involving COS intermediate mechanism, the abundant elemental sulfur was produced by the SO2 reduction by COS which was produced in the second step and was more effective reducing agent than CO.