A mechanistic study on kinetic compensation effect during low-temperature oxidation of coal chars
A mechanistic study on kinetic compensation effect during low-temperature oxidation of coal chars
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DOI：
10.1016/j.proci.2010.07.073
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
K. Yip;E. Ng;Chun-Zhu Li;J. Hayashi;Hongwei Wu
中科院分区：
文献类型：
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作者：
K. Yip;E. Ng;Chun-Zhu Li;J. Hayashi;Hongwei Wu
本文提供了一系列碳材料（石墨，亚烟煤焦，褐煤焦）的低温氧化机理的见解。在化学反应控制的条件下，对快速热解半焦的氧化进行了动力学分析。采用FT-Raman光谱分析提供了整个氧化过程中反应碳材料的碳结构的直接结构信息。结果表明，在此条件下的选择性氧化的意义，并与此平行，碳氧化反应的动力学补偿效应，在整个转化的所有样品。由FT-拉曼光谱的结果支持，动力学补偿效应似乎是这些具有异质碳结构的碳材料的选择性氧化的结果。氧化的所有样品，有或没有催化剂，似乎是类似的“性质”的碳结构缩合在低温氧化过程中，这表明类似的增加表观活性位点的人口相对于增加表观能垒。在现有的实验条件下，推导出了适用于各种材料的通用动力学补偿效应关联式，只需要初始焦炭动力学参数。焦炭中固有的无机物种似乎也改变了选择性氧化的结果碳结构缩合的“程度/范围”。在这种情况下，使用的补偿效应相关性将需要更多的信息，在氧化过程中的催化，除了初始炭动力学参数。
This paper provides mechanistic insights into the low-temperature oxidation of a range of carbon materials (graphite, a sub-bituminous coal char, and a brown coal char). Kinetic analysis was carried out on oxidation of the chars, prepared from fast-heating pyrolysis, under chemical-reaction-controlled regime. FT-Raman spectroscopic analysis was adopted to provide direct structural information on the carbon structure of reacting carbon materials throughout oxidation. The results demonstrate the significance of selective oxidation under the conditions, and parallel to this, the kinetic compensation effect of carbon oxidation reaction throughout conversion for all samples. Supported by the results from FT-Raman spectroscopy, the kinetic compensation effect seems to be a result of the selective oxidation of these carbon materials with heterogeneous carbon structures. Oxidation of all samples, with or without catalysts, appears to be similar in terms of the ‘nature’ of carbon structural condensation during low-temperature oxidation, suggesting a similar increase in apparent active sites population with respect to increase of apparent energy barrier. Under the current experimental conditions, a general kinetic compensation effect correlation has been deduced for various materials, requiring only the initial char kinetic parameters. The inherent inorganic species in chars also seem to alter the ‘degree/extent’ of carbon structural condensation as results of selective oxidation. In this case, the use of the compensation effect correlation will require more information on the catalysis during oxidation, apart from the initial char kinetic parameters.