Reduction of SO₂ on different carbons

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• 作者：Humeres ; Eduardo ; Moreira ; Regina F.P.M. ; da Gloria B. Peruch ; Maria
• 关键词：A. Charcoal ; Graphite ; Coke ; D. Reactivity ; Reaction kinetics
• 刊名：Carbon
• 出版年：2002
• 出版时间：April, 2002
• 年：2002
• 卷：40
• 期：5
• 页码：751-760
• 全文大小：163 K

文摘

The reduction of SO₂ on four carbons (graphite, charcoal, activated carbon and coke) was studied under steady-state conditions and when the kinetics was chemically controlled in a reactor operated under differential conditions. The reaction showed second-order kinetics: first order with respect to carbon and first order with respect to the partial pressure of SO₂. The reactivity of the different carbons, as measured by the second-order rate constants, followed the sequence of decreasing crystallinity: graphite<coke (7.34)<coke (11.73)<charcoal. The difference in reactivity between graphite and charcoal was determined by ΔH^≠, while for cokes it increased with the ash content because of a favorable ΔS^≠. The main reaction products for all carbons were CO₂ and sulfur in the ratio 2:1, considering the sulfur as S₂, which was shown to be formed through the same path. CO, COS, and CS₂ were also detected, and the product distribution depended on the carbon and whether the reaction was diffusion controlled or chemically controlled. Analysis of product ratios strongly suggested that CO, COS and CS₂ were produced from consecutive reactions of the primary products. CO was formed from CO₂ by a slow Boudouard reaction that occurred partially and under conditions of non-equilibrium. Complexed sulfur reacted with CO to form COS and CS₂. There was an interaction between the active site of reduction and the site where sulfur is inserted.