Carbonyl node and decarbonylation bottleneck: A mechanistic basis for staged gas release in coal
5 affiliations
- 1School of Safety Science & Engineering
- 2Xi’an University of Science and Technology
- 3Mechanical Engineering Department
- 4Texas A&M University
- 5Qinghai Energy Development (Group) Co. Ltd
Abstract
Coal spontaneous combustion begins with low-temperature oxidation, in which multiple functional groups participate concurrently, and their coupled evolution ultimately determines the formation of diagnostic gases. However, how these pathways interact and translate structural oxidation into staged gas release remains poorly resolved. Here, the oxidation pathways associated with methyl, hydroxyl, ether, and carbonyl functionalities in Liuqiao (LQ) coking coal are integrated into a unified reaction network. Site-specific lead compounds representing the corresponding local coal environments were constructed, and Laplacian bond order (LBO) was used to identify preferred activation sites. Density functional theory calculations characterized the elementary reaction pathways, with transition states verified by intrinsic reaction coordinate analysis where applicable. LBO identified distinct activation centers for each functionality, while the three supply pathways exhibited closely convergent propagation barriers of 16.84, 17.71, and 17.68 kcal/mol, indicating concurrent operation with contributions governed primarily by functional-group abundance rather than strong kinetic selectivity. Peroxide homolysis acts as a kinetic gate at 33.50 kcal/mol, whereas carbonyl formation is facile and decarbonylation constitutes the downstream bottleneck at 22.47 kcal/mol. This network architecture predicts that carbonyl species should accumulate before substantial CO release. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and TG-MS confirm this prediction, showing carbonyl accumulation preceding the staged evolution of H2O, CO, and CO2. These results establish carbonyl as a key structural reservoir linking low-temperature oxidation chemistry to gas evolution and provide a mechanistic basis for interpreting gas-based indicators of coal spontaneous combustion.
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BibTeX
@misc{li2026carbonyl,
title = {{Carbonyl node and decarbonylation bottleneck: A mechanistic basis for staged gas release in coal}},
author = {Yaqing Li and Tingting Huang and Jun Deng and Yutao Zhang and Seyed Borhan Mousavi and Saeed Zeinali Heris and Kexin Liu and Xiangqing Jiang},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008993/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008993/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Carbonyl node and decarbonylation bottleneck: A mechanistic basis for staged gas release in coal
AU - Yaqing Li
AU - Tingting Huang
AU - Jun Deng
AU - Yutao Zhang
AU - Seyed Borhan Mousavi
AU - Saeed Zeinali Heris
AU - Kexin Liu
AU - Xiangqing Jiang
PY - 2026
DA - 2026/09/17
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008993/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008993/v1
AB - Coal spontaneous combustion begins with low-temperature oxidation, in which multiple functional groups participate concurrently, and their coupled evolution ultimately determines the formation of diagnostic gases. However, how these pathways interact and translate structural oxidation into staged gas release remains poorly resolved. Here, the oxidation pathways associated with methyl, hydroxyl, ether, and carbonyl functionalities in Liuqiao (LQ) coking coal are integrated into a unified reaction network. Site-specific lead compounds representing the corresponding local coal environments were constructed, and Laplacian bond order (LBO) was used to identify preferred activation sites. Density functional theory calculations characterized the elementary reaction pathways, with transition states verified by intrinsic reaction coordinate analysis where applicable. LBO identified distinct activation centers for each functionality, while the three supply pathways exhibited closely convergent propagation barriers of 16.84, 17.71, and 17.68 kcal/mol, indicating concurrent operation with contributions governed primarily by functional-group abundance rather than strong kinetic selectivity. Peroxide homolysis acts as a kinetic gate at 33.50 kcal/mol, whereas carbonyl formation is facile and decarbonylation constitutes the downstream bottleneck at 22.47 kcal/mol. This network architecture predicts that carbonyl species should accumulate before substantial CO release. In-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and TG-MS confirm this prediction, showing carbonyl accumulation preceding the staged evolution of H2O, CO, and CO2. These results establish carbonyl as a key structural reservoir linking low-temperature oxidation chemistry to gas evolution and provide a mechanistic basis for interpreting gas-based indicators of coal spontaneous combustion.
ER -