Effect of cell geometry on the in situ measurement of e.s.r.-free radical concentrations during pyrolysis of a ZnCl2-impregnated coal

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

doi:10.1016/0016-2361(88)90047-6

Cited by 6 publications

(2 citation statements)

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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%

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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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