Reduction of SO₂ by CO to Elemental Sulfur over Sn-Zr Catalysts

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Sn-Zr catalysts with Sn/Zr molar ratio of 1/4, 3/5, 1/1 and 2/1 were selectively prepared. The reactivity of Sn-Zr catalysts in accordance with experimental conditions such as reaction temperature (573-823 K) and space velocity (GHSV: 10,000 cm³·g-cat^-1·h^-1) was investigated. Sn-Zr catalysts exhibited high activity and yield in the reduction of SO₂ to elemental sulfur. SO₂ conversion and sulfur yield in the recovery of elemental sulfur from SO₂ over Sn₂Zr₁ catalyst were respectively about 99 % and 97.5 % at 598 K, which were superior to other catalysts. Crystalline phases observed were tin dioxide and zirconium dioxide. TEM showed that fine particles of 5-20 nanometers in round shapes were present in the sample before and after the reaction. This indicates that no sintering of the catalyst occurred. From the TPR results, two peaks were observed. The first peak appeared at around 580-620 K is considered due to the partially reduction of SnO₂ to SnO. The second peak at around 1025 K is attributable to the reduction of SnO to metallic Sn.