A study on the characteristics of the SO2 reduction using coal gas over SnO2-ZrO2 catalysts

SO2, which is an air pollutant causing acid rain and smog, can be converted into elemental sulfur in direct sulfur recovery process (DSRP). SO2 reduction was performed over catalyst in DSRP. In this study, SnO2-ZrO2 catalysts were prepared by a co-precipitation method, and CO and coal gas, which contains H2, CO, CO2 and H2O, were used as reductants. The reactivity profile of the SO2 reduction over the catalysts was investigated at the various reaction conditions as follows: reaction temperature of 300–550 °C, space velocity of 5000–30,000 cm3/g-cat. h, [reductant]/[SO2] molar ratio of 1.0–4.0 and Sn/Zr molar ratio of SnO2-ZrO2 catalysts 0/1, 2/8, 3/5, 5/5, 2/1, 3/1, 4/1 and 1/0. SnO2-ZrO2 (Sn/Zr = 2/1) catalyst showed the best performance for the SO2 reduction in DSRP on the basis of our experimental results. The optimized reaction temperature and space velocity were 325 °C and 10,000 cm3/g-cat. h, respectively. The optimal molar ratio of [reductant]/[SO2] varied with the reductants, that is, 2.0 for CO and 2.5 for coal gas. SO2 conversion of 98% and sulfur yield of 78% were achieved with the coal gas.