Catalytic reduction of SO2 over Sn–Zr based catalysts for DSRP under high pressure

The catalytic activity of Sn–Zr based catalysts and the production behavior of COS during SO2 reduction were investigated for the catalytic reduction of SO2 under high pressure condition in this study. The SnO2, ZrO2 and SnO2–ZrO2 used as the catalysts were prepared by the precipitation and co-precipitation methods. The activity tests for the Sn–Zr based catalysts were carried out in the range of 200–450 °C at atmospheric pressure and 20 atm. CO was also used as the reducing agent for the reduction of SO2. The catalytic activity and a surface area of the SnO2–ZrO2 prepared by the co-precipitation methods were higher than that of the SnO2 and SnO2–ZrO2 catalysts prepared by the physical mixing. It was concluded that the surface area of SnO2–ZrO2 catalyst prepared by the co-precipitation increased due to the formation of the lattice defects. A high yield of elemental sulfur was also maintained for 50 h in the durability test. Carbonyl sulfide is produced by the reaction between CO and the elemental sulfur produced during the reduction of SO2, and was also produced by the gas–solid reaction between the metal sulfide and CO. The selectivity of COS was high at the intermediate level of conversion of SO2. Since the vapor pressure of elemental sulfur decreased with increasing pressure, the production of COS was reduced to a greater extent at the high SO2 conversion observed at high pressure. From these results, it was confirmed that SnO2–ZrO2 is a suitable catalyst for the catalytic reduction of SO2 at high pressure.