In Situ FTIR Study of Real-Time Changes of Active Groups during Oxygen-Free Reaction of Coal

Qi, Xuyao; Wang, Deming; Xin, Haihui; Qi, Guansheng

doi:10.1021/ef400534f

Cited by 78 publications

(29 citation statements)

References 51 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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.

Self Cite

View full text Add to dashboard Cite

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 ...

show abstract

Section: Computational Objectmentioning

confidence: 99%

Reaction pathways of hydroxyl groups during coal spontaneous combustion

Xue

Xin

et al. 2016

Can. J. Chem.

Self Cite

View full text Add to dashboard Cite

show abstract

“…[24,25] Here we will only describe it in short. The main part in the in situ FT-IR system includes an in situ reaction chamber, a gas providing tube, and a programmed heater.…”

Section: The In Situ Ft-ir Systemmentioning

confidence: 99%

“…In consideration of this situation, an in situ FT-IR system of infrared spectrogram was used to test the micro changes during coal reaction at low temperatures. [24,25] Using the in situ FT-IR, the real-time changes of different functional groups during coal reaction under different atmospheres can be obtained exactly.…”

Section: Introductionmentioning

confidence: 99%

Oxidation and Self-Reaction of Carboxyl Groups During Coal Spontaneous Combustion

Wang

Xue

et al. 2014

Spectroscopy Letters

Self Cite

View full text Add to dashboard Cite

Carboxyl groups play an important role during the development of coal self-heating. The real-time changing characteristics of carboxyl groups were obtained using an in situ Fourier Transform Infrared Spectroscopy method. They are significantly influenced by reaction atmospheres. Under dry-air atmosphere, their quantity obviously decreases before reaching 120 C and then increases with temperature rise. Under oxygen-free atmosphere, it decreases before reaching 80 C and then increases with temperature rise. In contrast with direct oxidation process, the quantity of carboxyl groups is smaller and the decrease phenomenon at the beginning almost disappears during the oxidation process following oxygen-free reaction. The results indicate that the carboxyl groups have different reaction pathways during coal self-heating. These pathways can be divided into two kinds, that is, oxidation pathways and self-reaction pathways. The study proposed the reaction sequences of carboxyl groups during coal self-heating, which are helpful for revealing the mechanism of coal spontaneous combustion.

show abstract

“…Furthermore, the low-temperature oxidation of coal is closely related to the type of coal. The difference in the tendency of the spontaneous combustion of different coal types is mainly reflected by the content and occurrence of active groups and inherent oxygen-containing species (Kaji et al, 1985;Qi et al, 2013;Yuan and Smith, 2008).…”

Section: Introductionmentioning

confidence: 99%