Nature of the free radicals in coals, pyrolyzed coals, and liquefaction products

Conference · Mon Jan 01 04:00:00 EST 1979 · Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States)

OSTI ID:6086192

Retcofsky, H L ^[1]; Hough, M R; Clarkson, R B

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1. Pittsburgh Energy Technology Center, PA

In contrast to the ESR spectra of coals, which generally consist of a single line devoid of any resolvable fine structure due to hyperfine intreactions, the ENDOR spectra (at least in the present study) are rich in detail. These results are quite surprising in light of spectra published several months ago which showed only a single band at the so-called free proton frequency . In an attempt to experimentally deduce the reasons for this apparent discrepancy of results, we found a reversible effect of air (oxygen) on the ENDOR spectrum, i.e., the hyperfine lines were observed for evacuated samples, but disappeared upon admission of air to the samples. The fact that an ENDOR spectrum is observed under the experimental conditions employed is unambiguous proof that the unpaired electrons in the coal couple with nuclear spins, undoubtedly protons, in the sample. This provides additional support for the free radical interpretation of the ESR spectrum. The magnitude of the hyperfine interactions, i.e., none greater than 10 gauss, indicates that none of the radicals has a high unpaired electron spin density at a particular carbon atom.

• OSTI ID: 6086192
• Report Number(s): CONF-790415-P2
• Conference Information: Journal Name: Am. Chem. Soc., Div. Fuel Chem., Prepr.; (United States) Journal Volume: 24:1
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010600* -- Coal
Lignite
& Peat-- Properties & Composition
CARBONACEOUS MATERIALS
CHARS
CHEMICAL COMPOSITION
COAL
COAL LIQUIDS
ELECTRON SPIN RESONANCE
ENERGY SOURCES
FOSSIL FUELS
FUELS
MAGNETIC RESONANCE
PYROLYSIS PRODUCTS
RADICALS
RESONANCE
STRUCTURAL CHEMICAL ANALYSIS