The \u3csup\u3e13\u3c/sup\u3eC-NMR Solid State Spectroscopy of Various Classes of Coals

The 13C-NMR spectra of various classes of coal obtained in the solid state show two resonances, one of which is assigned to aromatic carbon and the other to aliphatic carbon. The resonances are very broad with the high field resonance centered at about 7 ppm below tetramethylsilane and a low field resonance centered at about 140 ppm below tetramethysilane. Based on our previous solid state 13C-NMR studies of graphite and diamond, the high field resonance is typical of a sp3 carbon whereas the low fields resonance is assigned to a sp2 carbon whereas the low fields resonance is assigned to a sp2 carbon. It is found that the antracitic coals have more aromatic (sp2) carbons than the bituminous, subbituminous and lignite coals. The analytical implications of this technique are briefly discussed