Low-temperature oxidation kinetics of high-volatile bituminous coal studied by dynamic in situ 9 GHz c.w. e.p.r. spectroscopy

Kudynska, J.; Buckmaster, H. A.

doi:10.1016/0016-2361(96)00014-2

Cited by 42 publications

(18 citation statements)

References 29 publications

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“…There are many works [1][2][3][10][11][12][13][14][15][16][17][18][19][20][21] about the application of EPR spectroscopy to study different chemical processes in coal. The difficult separation of component lines in complex EPR spectra of coal is probably responsible for the narrow range of these studies.…”

Section: Introductionmentioning

confidence: 99%

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

et al. 2003

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Changes in individual groups of paramagnetic centers after reduction and reductive butylation of Polish flame coal (70.8 wt.% C) were studied by electron paramagnetic resonance (EPR) spectroscopy. The modero method of reductive butylation of coal in a potassium-liquid ammonia system was used. This process increases the solubility of coal in organic solvents. Microwave saturation of EPR spectra was applied to test the spin-lattice relaxation in coal. The measured EPR spectra were a superposition of broad (ABpp, 0.424).49 mT) and narrow (ABpp, 0.09-0.13 toT) Lorentz lines. Paramagnetic centers located in simple and multiring aromatic structures were responsible for the broad and narrow lines, respectively. Microwave saturation indicates that slow and fast spin-lattice relaxation processes are characteristic for these two types of structures in the original coal. A decrease of the microwave power saturation of the broad Lorentz line after a single reduction of coal was observed. It inereased for both 4 times reduced coal and reductively butylated coal. As the result of multiple reduction and butylation, spin-lattice relaxation processes in simple coal aromatic units were fastened. The narrow Lorentz lines of both 4 times reduced and reductively butylated coal were saturated and the spin-lattiee relaxation time increased.

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Section: Introductionmentioning

confidence: 99%

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

et al. 2003

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“…It is generally accepted that peroxides (−O−O−) are the first intermediates formed because of the coupling of the biradical oxygen molecule with a free carbon center in the aromatic or aliphatic structure of coal during chemisorption. 35 The α-methylene component has the highest reactivity and reacted with O 2 to form peroxides (−O−O−). 22 This is followed by the abstraction of a hydrogen atom by a peroxide radical from aromatic or aliphatic groups, leading to the formation of hydroperoxides (−O−O−H), as shown in reaction 4.…”

Section: Resultsmentioning

confidence: 99%

“…It is generally accepted that peroxides (−O–O−) are the first intermediates formed because of the coupling of the bi-radical oxygen molecule with a free carbon center in the aromatic or aliphatic structure of coal during chemisorption . The α-methylene component has the highest reactivity and reacted with O 2 to form peroxides (−O–O−) .…”

Section: Resultsmentioning

confidence: 99%

Study on the Chemical Inhibition Mechanism of DBHA on Free Radical Reaction during Spontaneous Combustion of Coal

Wang

Zhou

et al. 2020

Energy Fuels

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It is imperative to have an in-depth understanding of the chemical inhibition mechanism for spontaneous combustion of coal, not only for controlling and preventing spontaneous combustion of coal in the coal mining industry but also for reducing emissions of hazardous gases. N,N-dibenzylhydroxylamine (DBHA) as a hydroxylamine free radical scavenger can be chosen as a feasible stabilizer for the spontaneous combustion of coal. In this study, the inhibitory performance of DBHA was examined by investigating coal mass changes and heat release obtained from thermogravimetric and differential scanning calorimetry. The effect of DBHA on change of the active groups during coal oxidation at different temperatures was determined by in situ Fourier-transform infrared spectroscopy. Density functional theory was also introduced to optimize the active radical model and calculate thermodynamic parameters. Experimental results showed that DBHA exerted a strong inhibitory effect on the spontaneous combustion of coal, especially for lignite and sub-bituminous coal. DBHA can combine with a hydroperoxide intermediate to form a stable compound, causing the effect of reducing the free hydroxyl content in coal and interrupting the formation of aldehydes and carboxylic acids. Additionally, it can combine with alkyl radicals to form stable compounds. DBHA exhibits an inhibitory effect by increasing the activation energy at each stage, especially during the accelerated oxidation and quick oxidation stages. Furthermore, the possible reaction paths between free radicals and DBHA were also proposed on the basis of the experimental findings.

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“…Low-temperature oxidation of coal is the primary source of heat leading to spontaneous combustion. Several investigators have proposed a number of coal oxidation mechanisms at low temperatures [27][28][29][30][31][32][33][34][35]. In general, two parallel reaction sequences were supposed to occur in the self-heating of coal, i.e.…”

Section: Reaction Rate Of Coal Oxidationmentioning

confidence: 99%

A rapid method for determining the R70 self-heating rate of coal

Xin

Wang

et al. 2013

Thermochimica Acta

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Low-temperature oxidation kinetics of high-volatile bituminous coal studied by dynamic in situ 9 GHz c.w. e.p.r. spectroscopy

Cited by 42 publications

References 29 publications

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

Effect of reduction and butylation on coal: Application of microwave saturation of two-component EPR spectra

Study on the Chemical Inhibition Mechanism of DBHA on Free Radical Reaction during Spontaneous Combustion of Coal

A rapid method for determining the R70 self-heating rate of coal

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