Detection of weathering in stockpiled coals by Fourier transform infrared spectroscopy

Ibarra, JoséV.; Miranda, JoséL.

doi:10.1016/0924-2031(95)00060-7

Cited by 65 publications

(68 citation statements)

References 16 publications

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“…Table 6 shows the evolution of the H al /Car ratio (2800-3000 cm -1 zone/1610 cm -1 band) of the three coals. It can be observed that this ratio decreased with temperature, indicating a significant disappearance of aliphatic structures when increasing the oxidation intensity, in agreement with the reported mechanisms for coal oxidation [29][30][31] . When fresh coal was exposed to air, oxygen adsorption occurred initially on aliphatic C-H forming intermediate products such as peroxide or hydroperoxide.…”

Section: Dynamic Characteristics Of Molecular Hydrogensupporting

confidence: 89%

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

Wang

Xue

et al. 2017

Energy Fuels

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Although H2 gas is used in coal mines as an important indicator to reflect the state of coal spontaneous combustion, the gas production of H2 at low temperature has been scarcely reported in the literature. In this paper, the modes and release mechanism of molecular hydrogen were investigated for three different coal ranks below 200 °C. Batch reactor tests were performed in combination with chromatographic analysis of the coal oxidation process. The experimental results showed that molecular hydrogen release mainly originated from coal oxidation rather than thermal decomposition of inherent hydrogen-containing groups. The amount of hydrogen released increased with the coal rank. The H2 release process during low-temperature oxidation typically proceeds in two phases, namely H2 slow release (T < 100 °C) and H2 accelerated release (T > 100 °C) phases. Experiments with model compounds revealed aldehyde compounds to noticeably produce H2. Coal plays a positive role in promoting the aldehyde groups to release H2 and CO2, but an opposite trend was observed in the case of CO. As revealed by Fourier transform infrared (FTIR) spectroscopy, the amount of aliphatic structures significantly decreased with the oxidation intensity, and a drastic increase in the aldehyde content was found at temperatures above 120 °C. Additionally, the path for the formation of H2 during low-temperature oxidation of coal was provided.

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Section: Dynamic Characteristics Of Molecular Hydrogensupporting

confidence: 89%

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

Wang

Xue

et al. 2017

Energy Fuels

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“…This result implies that two mechanisms of oxidation and decomposition proceed simultaneously during the thermal treatment process of lignite in air atmosphere. Oxidation of active aliphatic parts (especially methyl and methylene) in the organic structure of coals results in the additional formation of oxygen-containing groups [31,32] . Oxygen absorption occurs initially on methylene groups to produce free radicals for further formation of hydroperoxide, eventually leading to generating oxygen groups involving carboxyl and carbonyl [32] .…”

Section: Changes Of Oxygen-containing Groups During Lignite Upgradementioning

confidence: 99%

“…Oxidation of active aliphatic parts (especially methyl and methylene) in the organic structure of coals results in the additional formation of oxygen-containing groups [31,32] . Oxygen absorption occurs initially on methylene groups to produce free radicals for further formation of hydroperoxide, eventually leading to generating oxygen groups involving carboxyl and carbonyl [32] . Some researches indicate that oxidization of methylene bridges in aromatic units will cause an increase of phenolic hydroxyl groups which evolve to quinone and ultimate carboxyl with the deepening of oxidation [27] .…”

Section: Changes Of Oxygen-containing Groups During Lignite Upgradementioning

confidence: 99%

Changes of oxygen-containing groups during thermal treatment and their influences on moisture readsorption of lignite

2015

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The changes of oxygen-containing groups in the thermal treatment process of lignite were analysed and the moisture re-adsorption amounts of upgraded coals were related in this study. Chemical titration method was applied to determine the types and contents of oxygen-containing groups in raw lignite and upgraded coals obtained in the temperature range of 353-633K and under atmospheres of argon, air and carbon dioxide respectively.Experimental results showed that the oxygen-containing groups mainly involved carbonyl, phenolic hydroxyl and carboxylic groups (including carboxyl and carboxylate), among which phenolic groups were dominant. These different oxygen-containing groups decomposed discriminatingly with temperature according to thermal stability. The removal of oxygen-containing groups proceeded more easily in CO 2 atmosphere compared with that in Ar. Oxidation reaction occurring on the surface of lignite exposed to air leaded to the increase of oxygen-containing groups. The different types of Downloaded by [New York University] at 17:58 28 July 2015 2 oxygen-containing groups possessed the variously combining ability with water, among which carboxyl was considered as the most important group for the moisture re-adsorption. Decomposition of oxygen-containing groups in thermal treatment process of lignite mainly caused the reduction of monolayer water adsorption and further decreases the multilayer water.

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“…Some different methods have been used in analyzing the infrared spectrograms. [18,20,21,[29][30][31] Three processing methods were used in the data processing of the infrared spectrogram. We separated the overlapping parts in spectrograms and enhanced their resolving ability using the Fourier self-deconvolution method.…”

Section: Distribution Of Functional Groups In Beizao Lignitementioning

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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Detection of weathering in stockpiled coals by Fourier transform infrared spectroscopy

Cited by 65 publications

References 16 publications

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

Experimental Study on the Molecular Hydrogen Release Mechanism during Low-Temperature Oxidation of Coal

Changes of oxygen-containing groups during thermal treatment and their influences on moisture readsorption of lignite

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

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