Abstract The caking property is a prerequisite and essential condition for coal to form coke. Investigating the impact of different functional group structures in coking coal on its caking property would be help to optimize coal blended, while the functional group structures of coal samples was used to characterize through Fourier transform infrared spectroscopy (FT-IR). The changes in these structures were investigated on eight coking coals of varying degrees of metamorphism during high-temperature pyrolysis in this paper. The peak fitting of infrared spectra was used to derive the structural parameters of the functional groups in the coal. Multivariate linear regression was then employed to analyze the correlation between different functional group structures and caking property (G value). The results demonstrated that the infrared parameters aromatic hydrogen rate (<InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11955_2025_10701_Article_IEq1.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\(f_{{{\text{ar}}}}^{{\text{H}}}\)</EquationSource>  </InlineEquation>), aromatic carbon rate (<InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11955_2025_10701_Article_IEq2.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(f_{{{\text{ar}}}}^{{\text{C}}}\)</EquationSource>  </InlineEquation>), aromaticity (AR), the degree of aromatic ring condensation (DOC), and the length of the aliphatic chain or the branching degree of aliphatic chains (F) increased, when the longer aliphatic chains would break down into more short aliphatic chains during pyrolysis. Multivariate linear regression analysis revealed that the caking property G value of coking coal could be primarily determined by the length of the aliphatic chain or the branching degree of aliphatic chains, with secondary factors being the content of hydrogen bonds and aliphatic content. A higher aliphatic side chains content, primarily short aliphatic chains, a high degree of branching, and a significant amount of hydrogen bonds would be beneficial for generating more plastic layer, thereby enhancing the coal’s caking property. Therefore, the established regression model indicated that when the relative content of aliphatic groups in coking coal was around 0.50–0.65, the degree of branching was around 2.0, and the relative content of hydrogen bonds was between 1.5–4.0, the coal caking property G value was between 65~80, which could guide coal blending and coking from the perspective of coal molecular functional group structure.

Effect of Different Coking Coal Functional Groups Structure on Caking Property

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发表日期：

2025年7月1日

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Yan Peng,
XinTing Liu,
Yinping Cao,
XiaoYong Zhang,
DaiLin Zhang

摘要

Abstract

The caking property is a prerequisite and essential condition for coal to form coke. Investigating the impact of different functional group structures in coking coal on its caking property would be help to optimize coal blended, while the functional group structures of coal samples was used to characterize through Fourier transform infrared spectroscopy (FT-IR). The changes in these structures were investigated on eight coking coals of varying degrees of metamorphism during high-temperature pyrolysis in this paper. The peak fitting of infrared spectra was used to derive the structural parameters of the functional groups in the coal. Multivariate linear regression was then employed to analyze the correlation between different functional group structures and caking property (G value). The results demonstrated that the infrared parameters aromatic hydrogen rate ( \(f_{{{\text{ar}}}}^{{\text{H}}}\) ), aromatic carbon rate ( \(f_{{{\text{ar}}}}^{{\text{C}}}\) ), aromaticity (AR), the degree of aromatic ring condensation (DOC), and the length of the aliphatic chain or the branching degree of aliphatic chains (F) increased, when the longer aliphatic chains would break down into more short aliphatic chains during pyrolysis. Multivariate linear regression analysis revealed that the caking property G value of coking coal could be primarily determined by the length of the aliphatic chain or the branching degree of aliphatic chains, with secondary factors being the content of hydrogen bonds and aliphatic content. A higher aliphatic side chains content, primarily short aliphatic chains, a high degree of branching, and a significant amount of hydrogen bonds would be beneficial for generating more plastic layer, thereby enhancing the coal’s caking property. Therefore, the established regression model indicated that when the relative content of aliphatic groups in coking coal was around 0.50–0.65, the degree of branching was around 2.0, and the relative content of hydrogen bonds was between 1.5–4.0, the coal caking property G value was between 65~80, which could guide coal blending and coking from the perspective of coal molecular functional group structure.