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- Title
Reaction pathways of hydroxyl groups during coal spontaneous combustion.
- Authors
Qi, Xuyao; Xue, Haibo; Xin, Haihui; Wei, Cunxiang
- Abstract
Hydroxyl groups are one of the key factors for the development of coal self-heating, although their detailed reaction pathways are still unclear. This study investigated the reaction pathways in coal self-heating by the method of quantum chemistry calculation. The Ar-CH2-CH(CH3)-OH was selected as a typical structure unit for the calculation. The results indicate that the hydrogen atoms in hydroxyl groups and R3-CH are the active sites. For the hydrogen atoms in hydroxyl groups, they are directly abstracted by oxygen. For hydrogen atoms in R3-CH, they are abstracted by oxygen at first and generate peroxy-hydroxyl free radicals, which abstract the hydrogen atoms in hydroxyl groups later. The reaction of R3-CH contains three elementary reactions, i.e., the hydrogen abstraction of R3-CH by oxygen, the conjugation reaction between the R3C■ and oxygen atom, and the hydrogen abstraction of -OH by hydroxyl free radicals. Then, the microstructure parameters, IRC pathways, and reaction dynamic parameters were respectively analyzed for the four reactions. For the hydrogen abstraction of -OH by oxygen, the enthalpy change and activation energy are 137.63 and 334.44 kJ/mol, respectively, which will occur at medium temperatures and the corresponding heat effect is great. For the reaction of R3-CH, the enthalpy change and the activation energy are −3.45 and 55.79 kJ/mol, respectively, which will occur at low temperatures while the corresponding heat influence is weak. They both affect heat accumulation and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.
- Subjects
ACTIVATED adsorption; ELEMENTARY reactions (Chemical reactions); QUANTUM theory; THERMODYNAMICS; ELECTROMAGNETIC waves
- Publication
Canadian Journal of Chemistry, 2016, Vol 94, Issue 5, p494
- ISSN
0008-4042
- Publication type
Article
- DOI
10.1139/cjc-2015-0605