Low temperature processes in a bituminous coal studied by in situ electron spin resonance spectroscopy

Fowler, Timothy G.; Bartle, Keith D.; Kandiyoti, R.

doi:10.1016/0016-2361(87)90188-8

Cited by 40 publications

(16 citation statements)

References 9 publications

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“…The narrow EPR lines of multiring coal structures with high aromaticity characterized the fast spin-lattice relaxation processes and these lines saturated at higher microwave powers (16). Conversion of chemical structure during thermal decomposition of macerals and coals was accompanied by changes of the amount and properties of their paramagnetic centers (11,12,(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33). The strongest changes of concentration of paramagnetic centers in the studied macerals heated at 300 -650°C occured above 550°C (28 -33).…”

Section: Discussionmentioning

confidence: 99%

Thermally Excited Multiplet States in Macerals Separated from Bituminous Coal

Wiȩckowski

Pilawa

Świa̧tkowska

et al. 2000

Journal of Magnetic Resonance

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Section: Discussionmentioning

confidence: 99%

Thermally Excited Multiplet States in Macerals Separated from Bituminous Coal

Wiȩckowski

Pilawa

Świa̧tkowska

et al. 2000

Journal of Magnetic Resonance

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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%

“…The difficult separation of component lines in complex EPR spectra of coal is probably responsible for the narrow range of these studies. Changes of the total amount of paramagnetic centers in coal and changes in their resultant EPR spectra were mainly analyzed [14][15][16][17][18]. The change of individual groups of paramagnetic centers in chemically treated coal is not well known so far.…”

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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“…The complexity lies in the fact that solid fuels have an internal combustion stage, which has a considerable effect on the gasification process. This stage is accompanied by the formation of radicals, which was confirmed by the studies on pyrolysis and gasification of biomass and coal in the presence of hydrogen radical [2], as well as by the in situ spectroscopy of electronic paramagnetic resonance for the measurement of spin density on the fuel surface [3,4]. Therefore, during pyrolysis on the fuel surface and in the gas phase, there are free radicals, which can trigger the reactions among gaseous products of thermal decomposition.…”

Section: Introductionmentioning

confidence: 93%

Impact of gas-phase chemistry on the composition of biomass pyrolysis products

Козлов

Svishchev

Donskoy

et al. 2015

J Therm Anal Calorim

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In the present paper, significance of gas-phase chemical reactions occurring in thermal analysis furnace is evaluated. Free radical species form as a result of biomass thermal decomposition and may give rise to chain reactions. Gas portion emitted by the sample analyzed flows to detector (mass spectrometer in our study) in finite time interval, so chemical reactions may change its composition. Quantitative assessment of this change was made based on data about amount of active species that may initiate kinetic chains. Radical trap method was used to determine radical species amount. Toluene vapors was fed to carrier gas and flowed in thermal analysis furnace reacting with radical species produced from biomass thermal decomposition. Stable radical species-benzyl-is reaction product that can be detected by mass spectrometer. Results show that radical species concentration in gas produced from biomass gasification (639 ppm for pyrolysis stage and 3581 ppm for char gasification stage) is too small to change gas-phase composition significantly in time interval for which gas has been achieving detector. Comprehensive kinetic model for toluene oxidation in oxidizer lack conditions is developed based on widely known mechanisms. Radical species amount estimates may be useful as initial information in heterogeneous combustion modeling.

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Low temperature processes in a bituminous coal studied by in situ electron spin resonance spectroscopy

Cited by 40 publications

References 9 publications

Thermally Excited Multiplet States in Macerals Separated from Bituminous Coal

Thermally Excited Multiplet States in Macerals Separated from Bituminous Coal

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

Impact of gas-phase chemistry on the composition of biomass pyrolysis products

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