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7649142 
Journal Article 
SOLID-STATE C-13 NMR-STUDIES ON COAL AND COAL OXIDATION 
Macphee, JA; Kawashima, H; Yamashita, Y; Yamada, Y; , 
1993 
Yes 
Advances in Chemistry Series
ISSN: 0065-2393 
AMER CHEMICAL SOC 
WASHINGTON 
229 
323-339 
WOS:A1993KG26900017 
Conventional and dipolar-dephasing C-13 NMR spectra with cross-polarization and magic-angle spinning (CP-MAS) were recorded for the eight Argonne Premium coal samples at 300 MHz using a Bruker AC 300 spectrometer with 4-kHz sample spinning. Measured apparent aromaticities correlate well with the atomic H/C ratio (r = 0.96). Certain of these coals were subjected to oxidation in air at 100-degrees-C for 168 h. For the fresh coals, the aromatic carbons exhibit a two-component (Gaussian-Lorentzian) decay in the dipolar dephasing experiment. The oxidized coals, in the range of dipolar dephasing delays investigated, exhibit only a Gaussian decay. Aliphatic carbons of both fresh and oxidized coals exhibit only a single Gaussian component. This behavior is explained in terms of the increased radical concentration in the oxidized coals. Studies of the dipolar dephasing behavior of model aromatic compounds (eg., anthracene and naphthalene) were carried out, and the results of these help to interpret the results obtained for oxidized coals.