Hydrogen abstraction reaction mechanism of oil-rich coal spontaneous combustion

•The structural characteristics of oil-rich coal are revealed.•Key reaction links for hydrogen production of oil-rich coal are identified.•Hydroxyl radical is a pivotal intermediate for hydrogen production.•Hydrogen abstraction reaction mechanism of coal spontaneous combustion is found. Oil-rich coal is a type of coal with a hydrogen-rich structure, making it susceptible to spontaneous combustion at low temperatures. To investigate the process of hydrogen production through the low-temperature oxidation of oil-rich coal, nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR) experiments were conducted, along with quantum chemical simulations, to identify the dynamic changes in functional groups during low-temperature oxidation. The experimental results indicate that oil-rich coal primarily comprises hydrogen-containing structures, such as aromatic hydrocarbons and aldehyde groups. Based on the observed patterns of the functional group changes, three stages of hydrogen generation during the low-temperature oxidation of oil-rich coal were deduced. Furthermore, quantum chemical simulations were employed to model the target functional groups' structural changes during oil-rich coal's low-temperature oxidation. Combining the results of the experiments and simulations revealed the primary mechanism behind the low-temperature oxidation of oil-rich coal, leading to hydrogen production. This study identified the reaction of methylmethylene side chains forming aldehyde groups as a precursor to hydrogen. The simultaneous oxidation and structural interactions eventually result in the formation of hydrogen. These findings provide a more profound insight into the mechanism behind the spontaneous combustion of coal oxidation and provide a theoretical foundation for developing effective prevention and management technologies for the spontaneous combustion of oil-rich coal.