Research on the changes of free radicals during the oxygen-free heating process of coal
ZHU Lingqi
LIU Kexin
LI Yaxin
HAO Zi'ang
Abstract：To study the variation characteristics of free groups in coal during the oxygen-free heating process,long-flame coal was selected for thermogravimetric analysis and in-situ Fourier transform infrared spectroscopy experiments.The variation trends of functional groups between adjacent temperature points were analyzed by difference spectroscopy,and the quantitative data of func-tional groups changing with temperature were obtained by combining the Fourier transform infrared spectroscopy deconvolution technique.Further,the second-order derivative spectra and deconvolution spectra were utilized for segmented and peak-segmented fitting to explore the pyrolysis mechanism and kinetic characteristics of the main functional groups in different temperature intervals.The segmented and peak-segmented fitting research was conducted based on the second-order derivative spectra and deconvolution spectra.The results show that:during the entire heating process,the contents of aliphatic functional groups,hydroxyl groups(-OH),carbonyl groups(C=O),C-O and aromatic C=C in coal all decreased,while the content of aromatic C-H increased.The aliphatic groups decreased due to the volatilization of small molecule substances between 30-427℃,conforming to the unidirectional trans-port mode,and the activation energy was 22.7 kJ/mol;at 427-561℃,the single carbon-carbon bond breaks,resulting in a decrease in its quantity,which conforms to the third-stage reaction mode,and the activation energy rises to 82.46 kJ/mol;at 561-800℃,it conforms to the first-stage pyrolysis reaction,and the activation energy is 162.3 kJ/mol.The aromatic C=C decreases in quantity between 30℃and 427℃due to the cleavage of oxygen-containing functional groups and the volatilization of small mo-lecule substances;at 427-800℃,due to the decomposition of aliphatic functional groups resulting in a decrease in quantity,it con-forms to the secondary pyrolysis reaction mode,and the activation energy is 207.23 kJ/mol.The transformation of C-O to C=O and its decomposition between 30℃and 266℃reduces the quantity,which conforms to the first-stage pyrolysis reaction mode;at 266-800℃,due to the further reduction of pyrolysis of aliphatic functional groups,which conforms to the secondary reaction mode,the activation energy increases from 39.46 kJ/mol to 52.92 kJ/mol.The hydroxyl group(-OH)decreases in quantity due to water evaporation at 30-180℃,and decreases in quantity due to the decomposition of aliphatic functional groups at 180-561℃;at 266-800℃,this stage conforms to the secondary pyrolysis reaction mode,and the activation energy is 72.31 kJ/mol.
Keywords：chemical structure of coalfunctional groupFourier infrared spectroscopyactivation energylong-flame coal
Publication Date：2025-10-30
Online Publishing Date：2025-10-28(First online date of this platform, not the publication date of the document)
Pages：10( 105-114 )