期刊
FUEL
卷 331, 期 -, 页码 -出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.fuel.2022.125756
关键词
Coal oxidation; Free radicals; Model compounds; Oxidation pathway; Organic sulfur
The evolution mechanism of organic sulfur in the process of coal spontaneous combustion was investigated through quantum chemical calculations. The results showed that mercaptans play a dominant role in the oxidation process, and the oxidation of 2-methylthiophene releases the most heat.
In order to reveal the evolution mechanism of organic sulfur in the process of coal spontaneous combustion, the reaction paths and thermodynamic characteristics of 2-methylthiophene, dibenzothiophene, phenyl mercaptan, diphenyl sulfide, diphenyl sulfoxide, and diphenyl disulfide have been investigated by quantum chemical calculations. The results indicate C-H,-S-,-S-S-, S-H,-S-, and S=O bonds to be the respective active sites for oxidation reactions of the six model compounds. Upon oxidation and heating, 2-methylthiophene and phenyl mercaptan undergo dehydrogenation reactions to form hydroxyl radicals. The oxidation of organic sulfur com-pounds involves multiple steps; mercaptans are converted into thioethers, and thioethers and thiophenes are converted into sulfoxides and sulfones. The activity order of the six organic sulfur compounds is diphenyl sulfoxide > phenyl mercaptan > diphenyl sulfide > dibenzothiophene > 2-methylthiophene > diphenyl disulfide, with corresponding activation energies of 21.00, 60.39, 76.14, 94.52, 102.39, and 202.16 kJ/mol, respectively. It can be concluded that diphenyl sulfoxide is the most reactive and is easily oxidized to the cor-responding sulfone, but is only present at low levels in coal. Therefore, mercaptans play the dominant role in the oxidation of coal. The oxidation of 2-methylthiophene releases the most heat of 181.16 kJ/mol, which serves to accelerate coal spontaneous combustion.
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