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In order to explore the characteristics of spontaneous combustion of Jurassic coal in northern Shaanxi with low metamorphic degree and high coke content, DSC differential scanning calorimeter and diffuse in situ infrared spectroscopy experiment were used to study and analyze the dynamic evolution law and interaction relationship between macroscopic thermal effect and microstructure in the spontaneous combustion process of different coal seams in northern Shaanxi. The results show that there are three characteristic temperature points in the heat flow curve during the spontaneous combustion of Jurassic coal in northern Shaanxi, which can be divided into four stages according to the characteristic temperature points. It was found that the consumption and production of functional groups in Jurassic coal oxidation process were mainly in the absorption bands of aliphatic hydrocarbon, aromatic hydrocarbon and oxygen-containing functional groups, and CH3, CH2, C–H, OH and C=O were the most active key functional groups in the process of coal oxidation. The dynamic correlation degree between heat flux intensity and key active groups is established by using dynamic grey correlation mathematics method. It is concluded that C=O bond has the highest correlation with heat flow intensity during coal oxidation, and has the greatest influence on heat flow intensity. The correlation values of the active groups CH3 and CH2 are second only to the C=O bond, and they are easy to react with oxygen, accompanied by the reaction heat. Although the correlation degree between C–H and OH bond is lower than that of C=O, CH3 and CH2 bond, the correlation degree value is also high, and has certain contribution to the coal reaction heat. These research results have important guiding significance for the development of targeted inhibitors for Jurassic coal spontaneous combustion disaster in northern Shaanxi. [ABSTRACT FROM AUTHOR]

• Gas products during spontaneous combustion of coal were studied. • The significant variation of active groups in spontaneous combustion of coal was studied. • The quantitative relationship between key active groups and gas products was established. • The mechanism of gas release from spontaneous combustion of coal was described. In order to reveal the internal relationship between the active groups and gas products in spontaneous combustion of coal, the correlation between the content of active functional groups and the production of gas products was studied by temperature programmed experiment and in situ infrared spectroscopy analysis experiment. The results show that there are three characteristic temperature points in the gas release curve of Jurassic coal spontaneous combustion in northern Shaanxi, which can be divided into slow oxidation stage, critical temperature stage, rapid oxidation reaction stage and combustion stage. CH 3 , CH 2 , C–H and OH are actively consumed in the spontaneous combustion of coal. C O gradually increased, which is an important oxidation product during Jurassic coal oxidation in northern Shaanxi. The chain length CH 2 /CH 3 is attacked and the fracture shortened, while the oxygen enrichment degree of C O/C C in coal increases gradually. The correlation values of key active groups of CH 3 , CH 2 , C–H, OH, C O, CH 2 /CH 3 , and C O/C C with oxygen, carbon and oxygen gases and alkane and olefin gases in the process of coal oxidation heating in different coal seams in northern Shaanxi during Jurassic period are obtained. The results show that CH 3 , CH 2 and CH 2 /CH 3 , are the main parts of oxygen molecules attacking and binding in the Jurassic coal oxidation process in northern Shaanxi, and the oxygen-rich products of coal decompose into carbon oxygen gas and alkane alkene gas. Due to the different activation energies of various active groups, the spontaneous combustion of coal shows different reaction degrees in each stage. The research results can be used to understand the occurrence and development degree of spontaneous coal combustion, and have important guiding significance for the monitoring and warning of spontaneous coal combustion and the targeted prevention and control of spontaneous coal combustion disasters. [ABSTRACT FROM AUTHOR]