Microscopic understanding of the reaction path and gas production mechanism of key functional groups in coal: Combination of molecular dynamics, quantum chemistry and experimental research

Investigating the influence of reactive groups on coal spontaneous combustion (CSC) and gas generation holds significant value for controlling coal fires and atmospheric pollution. Therefore, molecular dynamics and quantum chemistry are innovatively used to study the reaction pathway and gas production mode of key groups in coal from a microscopic perspective, and experiments are combined to further explore the potential reaction mechanism. These results indicate that reactive groups form radicals during the oxidation process, which subsequently undergo decomposition and condensation to initiate chain reactions. The gas production pathways involve direct oxidative decomposition and the breakdown of coal-oxygen complexes and peroxides. CO and CO2 are first produced at 333 K and 313 K, respectively, mainly from the thermal decomposition of carboxyl and aldehyde groups. Furthermore, the coal-oxygen complexation reaction has no energy barrier, and it can be carried out spontaneously at room temperature. The activation energy at the initial stage of the peroxide reaction is 109.4834 kJ / mol. When the coal temperature reaches 343 K, the hydroxyl and aldehyde group in coal began to undergo peroxide reaction. The activation energy of the dehydrogenation reaction of the active groups in the coal is 238.9205-302.1951 kJ / mol. When the coal temperature exceeds 343 K, the key primary groups in the coal can directly react with O2 to form more carbon oxygen free radicals and energy. The conclusions of this study provide theoretical support for the prevention of CSC and contribute to the promotion of safe coal production and environmental protection.