Chemical Structure and Properties of Heat Treated Coal in the Early State of Carbonization (V)
Electron Spiu Resonance of Coals
1966 Volume 45 Issue 12 Pages 876-883
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1966 Volume 45 Issue 12 Pages 876-883
The twelve Japanese coals over the range from lignite to anthracite, and six foreign coking and caking coals and anthracite were elected as coal sample. It seems to he considered from the shape variation due to saturation effect that ESR signal for foreign coals in vacuum (d.a.f. C=87.6%-90.7%) consists of at least two components. One of them is a broad component and the other is a narrow component. The latter is very sensitive to oxygen gas and disappears in air. The change due to oxygen gas is reversible. The value of peak.to.peak line width (ΔHmsl) for the latter is about 1-2 gauss and the spin center concentration is about 2-5×1017 spins/g. All the ESR signals show homogeneous saturation, althou gh it is vague for the signal consisting of two comonents. The spin-lattice relaxation time (T1) shows a maximum at about 86% C, which is slightly lower value than that obtained by Smidt and D. W. van Krevelen. The line width for Japanese coal bellow about 86% C is slightly broader as compared with their results. This result seems to be due to higher hydrogen content of Japanese coal . Above about 90% C, the spin center concentration (N) rapidly increases, the line width rapidly decreases and the shape of absorption line changes from Gaussian type to Lorentzian type . The N decreases with the increase of the volatile matter content and increases with the aromatic carbon fraction. The latter fact seems to show that the spin center concentration is connected with the formation of aromatic ring system.
