REDUCTION OF SULFUR-DIOXIDE BY CARBON-MONOXIDE TO ELEMENTAL SULFUR OVER COMPOSITE OXIDE CATALYSTS

The catalyst activity of fluorite-type oxide, such as ceria and zirconia, for the reduction of sulfur dioxide by carbon monoxide to elemental sulfur can be significantly promoted by active transition metals, such as copper. More than 95% elemental sulfur yield, corresponding to almost complete sulfur dioxide conversion, was obtained over a Cu-Ce-O oxide catalyst with a feed gas of stoichiometric composition ([CO]/[SO2] = 2) at temperatures above 450-degrees-C. This type of mixed metal oxide catalyst has stable activity and is resistant to water and carbon dioxide poisoning. XPS analysis found copper in the Cu-Ce-O oxide in a reduced oxidation state (Cu1+, Cu0). The stable fluorite-type structure, regarded as the backbone structure of the catalyst, existed in both the fresh and the spent catalyst. The high activity resulted from the strong interaction of transition metal and fluorite oxide.