Catalytic reduction of SO 2 over Sn–Zr based catalysts for DSRP under high pressure

Abstract

The catalytic activity of Sn–Zr based catalysts and the production behavior of COS during SO 2 reduction were investigated for the catalytic reduction of SO 2 under high pressure condition in this study. The SnO 2, ZrO 2 and SnO 2–ZrO 2 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 SO 2. The catalytic activity and a surface area of the SnO 2–ZrO 2 prepared by the co-precipitation methods were higher than that of the SnO 2 and SnO 2–ZrO 2 catalysts prepared by the physical mixing. It was concluded that the surface area of SnO 2–ZrO 2 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 SO 2, 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 SO 2. Since the vapor pressure of elemental sulfur decreased with increasing pressure, the production of COS was reduced to a greater extent at the high SO 2 conversion observed at high pressure. From these results, it was confirmed that SnO 2–ZrO 2 is a suitable catalyst for the catalytic reduction of SO 2 at high pressure.