Cross-polarization magic-angle spinning 13C NMR spectra of coals of varying rank

Abstract Cross-polarization, magic-angle spinning 13 C nuclear magnetic resonance spectra have been obtained on a series of coals that span the ASTM rank classification. Aromaticities thus obtained follow the classification reasonably well, increasing as rank increases NMR parameters were extensively varied to determine optimum conditions for the cross polarization contact time and pulse repetition rate. Good correlations were obtained between both the fixed carbon and the volatile matter obtained from the proximate analysis, and the aromatic carbon obtained from NMR. Generally the NMR spectra of lignites and low rank coals exhibit varying degrees of fine structure.