Self-reaction of initial active groups in coal

Qi, Xuyao; Wang, Biao; James, A Milke; Zhong, Xiaoxing

doi:10.1016/j.ijmst.2011.08.006

Cited by 28 publications

(12 citation statements)

References 14 publications

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“…It has been confirmed that the hydroxyl group is one of the main oxygen-containing groups and its basic characteristic parameters in the structure are almost the same in different ranks of coal. [33][34][35][36][37][38] Coal ranks affect the quantity of active groups existing in coal. The quantities of active groups in low-rank coals are usually larger than those in high-rank ones.…”

Section: Computational Objectmentioning

confidence: 99%

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Xue

Xin

et al. 2016

Can. J. Chem.

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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-CH 2 -CH(CH 3 )-OH was selected as a typical structure unit for the calculation. The results indicate that the hydrogen atoms in hydroxyl groups and R 3 -CH are the active sites. For the hydrogen atoms in hydroxyl groups, they are directly abstracted by oxygen. For hydrogen atoms in R 3 -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 R 3 -CH contains three elementary reactions, i.e., the hydrogen abstraction of R 3 -CH by oxygen, the conjugation reaction between the R 3 C▪ 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 R 3 -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.Résumé : Les groupes hydroxyle constituent l'un des principaux facteurs à l'origine du chauffage spontané du charbon. Toutefois, les mécanismes réactionnels précis de ce phénomène sont encore mal compris. La présente étude s'est penchée sur les mécanismes de réaction en cause dans le chauffage spontané du charbon en utilisant la méthode de calcul quantique de modélisation moléculaire. Nous avons choisi le Ar−CH 2 −CH(CH 3 )−OH comme unité structurale de référence pour le calcul. Les résultats indiquent que les atomes d'hydrogène des groupes hydroxyle et de la position R 3 −CH sont les centres réactifs. Les atomes d'hydrogène des groupes hydroxyle sont directement arrachés par l'oxygène. Quant aux atomes d'hydrogène de la position R 3 −CH, ils sont d'abord arrachés par l'oxygène et génèrent ensuite des radicaux libres peroxohydroxyle, qui arrachent à leur tour des atomes d'hydrogène des groupes hydroxyle. La réaction du R 3 −CH comprend trois réactions élémentaires : l'arrachement par l'oxygène de l'atome d'hydrogène de la position R 3 −CH, la réaction de conjugaison entre le radical R 3 C▪ et l'atome d'oxygène et l'arrachement de l'atome d'hydrogène du groupe -OH par les radicaux libres hydroxyle. Ensuite, nous avons analysé les paramètres microstructuraux, les voies de la coordonnée intrinsèque de réaction et les paramètres de dynamique de réaction ...

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Section: Computational Objectmentioning

confidence: 99%

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Xue

Xin

et al. 2016

Can. J. Chem.

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“…With respect to spontaneous combustion prediction in gob, fractal dimension (or Hurst index) can be used to indicate the oxidation condition of coal in slow oxidation stage in gob according to former researchers' study (Butakova et al, 2013;Chen et al, 2008;Wang et al, 2011;Qi et al, 2012;Zhu et al, 2010). If the fractal dimension of gas indexes exceeds its normal upper limit, then the coal will come to the quick oxidation stage indicating the rising risk of coal spontaneous combustion in gob.…”

Section: Critical Valuesmentioning

confidence: 99%

“…The process of coal spontaneous combustion is comprised of slow oxidation stage, quick oxidation stage and severe oxidation stage according to former studies (Butakova et al, 2013;Chen et al, 2008;Wang et al, 2011;Qi et al, 2012). Different oxidation phases are characterized by corresponding combustion gaseous products and their concentrations, which can be employed to indicate the stage of combustion (Zhu et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Coal spontaneous combustion prediction in gob using chaos analysis on gas indicators from upper tunnel

Yang

Zhou

et al. 2015

Journal of Natural Gas Science and Engineering

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“…[8][9][10][11][12][13][14] In order to further comprehend the reaction mechanism of spontaneous coal combustion, it is necessary to better understand the changes of these active groups during coal oxidation.…”

Section: Introductionmentioning

confidence: 99%

An In Situ Testing Method for Analyzing the Changes of Active Groups in Coal Oxidation at Low Temperatures

Wang

Xin

et al. 2014

Spectroscopy Letters

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This study details an in situ Fourier transform infrared spectroscopy analytical system that was employed to follow chemical variations in the functional groups on coal surface during the oxidation process at low temperatures. In the reported in situ Fourier transform infrared spectroscopy system, a special chamber was used to contain the coal powders, and a gas inlet tube and a programmable heater were used to simulate different reaction atmospheres and temperatures. The comparisons between in situ and ex situ Fourier transform infrared spectroscopy spectra indicate that the in situ Fourier transform infrared spectroscopy data offer a more accurate reflection of changes in the functional groups. The real-time changes of aliphatic hydrocarbon groups and oxygen-containing groups in a lignite coal sample were analyzed from 30 C to 220 C using in situ Fourier transform infrared spectroscopy. The experimental results indicate that the chemical variations in the functional groups are affected by their relative chemical activities. The results show that the presence of aliphatic groups on the coal surface varies with temperature. Over the range of 30-70 C the presence of these groups decreases, but then their abundance increases over the range of 70-180 C and finally decreases again when the temperature is increased to between 180 C and 220 C. With respect to oxygen-containing functional groups, three various trends were observed as the test temperature was varied. Our conclusion was that these variations are a function of the reaction activities of the various oxygen-containing functional groups.

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Self-reaction of initial active groups in coal

Cited by 28 publications

References 14 publications

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Coal spontaneous combustion prediction in gob using chaos analysis on gas indicators from upper tunnel

An In Situ Testing Method for Analyzing the Changes of Active Groups in Coal Oxidation at Low Temperatures

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