SELECTIVE CATALYTIC REDUCTION OF SULFUR-DIOXIDE WITH HYDROGEN TO ELEMENTAL SULFUR OVER CO-MO/AL2O3

The selective reduction of sulfur dioxide with hydrogen to elemental sulfur was studied over Co-Mo/Al2O3. When the feed conditions were properly optimized (SO2/H-2 mole ratio = 1:3), a sulfur yield of about 80% was achieved at temperatures around 300 degrees C. The temperature is the lowest that has been reported so far for any catalyst for this reaction. The catalytic activity remained high and stable after presulfiding with 10% H2S in hydrogen. Little influence on the catalytic activity was observed if the water content in the feed was kept below 11 vol.-%. The overall reaction consisted of two individual steps occurring on two different sites; sulfur dioxide was first hydrogenated to hydrogen sulfide on the metal sulfide phase, then followed by the Claus reaction of hydrogen sulfide with sulfur dioxide to produce elemental sulfur on the acidic sites of the alumina support.