To develop a new process for reducing high-concentration SO 2 to elemental sulfur, the reduction of SO 2 with CO and activated carbon in a fixed bed experimental system was investigated. The effects of temperature, CO/SO 2 molar ratio, and reaction time on SO 2 reduction were studied. The results showed that the starting temperature of SO 2 reduction with activated carbon was approximately 700 °C and that the addition of CO decreased the starting temperature to 400 °C. Higher temperature led to an increase in SO 2 conversion. The S yield also increased initially but then decreased when the temperature exceeded 800 °C, due to the formation of COS. SO 2 conversion increased with an increasing CO/SO 2 molar ratio, the optimum S yield being achieved at a CO/SO 2 ratio of 2. However, the existence of unreacted SO 2 in the product decreased the S yield and resulted in an optimum S yield occurring at a low ratio. Lower selectivity of SO 2 reduction to elemental sulfur was observed if reaction time was reduced. By prolonging gas−carbon contact time, the S yield increased and gradually approached SO 2 conversion at temperatures below 700 °C. The catalytic mechanism over activated carbon conformed to the COS intermediate mechanism, and the rate of the overall CO−SO 2 reaction was determined by the Claus reaction between COS and SO 2 .
The exponent-stabilized Koopmans' theorem (ESKT) is used to calculate the energies of n* temporary anion states of a series of substituted benzenes. The calculations yield fairly accurate predictions of the relative energies of x* states when using flexible sizes of basis sets.
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