Interpretation of Methane and Hydrogen Evolution in Coal Pyrolysis from the Bond Cleavage Perspective

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• 作者：Lei Shi ; Qingya LiuBin Zhou ; Xiaojin Guo ; Zhengke Li ; Xiaojie Cheng ; Ru Yang ; Zhenyu Liu
• 刊名：Energy & Fuels
• 出版年：2017
• 出版时间：January 19, 2017
• 年：2017
• 卷：31
• 期：1
• 页码：429-437
• 全文大小：583K
• ISSN：1520-5029

文摘

Pyrolysis of 34 coals of different rank with carbon contents of 73.7–91.9% was studied in a TG-MS system to analyze CH₄ and H₂ evolution. On the basis of the shape of evolution curves and dissociation energy of covalent bonds in coals, the CH₄ formation is attributed to the cleavage of a C_al–C_al bond in a low temperature range and that of C_al–C_ar bond in a high temperature range, while the H₂ formation was attributed to the cleavage of H–C_al bond in a low temperature range and that of C_al-C_ar bond in a high temperature range. The yields of CH₄ and H₂ corresponding to cleavage of each of these bonds are quantified by deconvolving each of the evolution curves into two subcurves. It is found that the cleavage of bonds containing only aliphatic carbon, such as C_al–C_al and H–C_al peaking at 549 and 540 °C, respectively, contributes to small fractions of CH₄ and H₂ generation. The cleavage of bonds containing an aromatic carbon, such as C_al–C_ar and H–C_ar peaking at temperatures of 618 and 774 °C, respectively, contributes to the major CH₄ and H₂ generation. The yields of the products and the proportion of each bond in the coals that cleaved to generate these products are found to be coal rank dependent. The changes of side-structure linked to these bonds are also analyzed with respect to changes in coal rank. These results extend the understanding on the mechanism of CH₄ and H₂ formation in coal pyrolysis as well as that on the bonding structure of coals.