FTIR and 13C NMR Investigation of Coal Component of Late Permian Coals from Southern China

Two separated components, vitrinite and barkinite, and one associated coal sample obtained from South China were studied by Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance ( 13 C NMR) with curve-fitting analysis to obtain information on the concentrations of several functionalities in the samples. These two components were also studied in situ in coal by micro-FTIR. Some parameters derived from FTIR, micro-FTIR, and 13 C NMR were selected to obtain a better understanding of the chemical structure of barkinite. All the FTIR and 13 C NMR spectra and the values of I 1 and I 2 show that the most distinct structural feature of barkinite is a rich concentration of aliphatic structures. Furthermore, the aliphatic structures are longer and less branched. Oxygen is mainly bound to aliphatic carbon. For barkinite, the ratio of integrated areas of 3000–2700 cm –1 and 3100–3000 cm –1 regions of FTIR spectra suggest that its aliphatic hydrogen concentration is larger than its aromatic hydrogen concentration. In the aromatic structures, barkinite has a higher ratio of integrated areas of 900–700 cm –1 to 1600 cm –1 than vitrinite, and the aromatic ring number per cluster is mainly 2 or 3. In addition, the intensity of the aliphatic peaks relative to the aromatic peaks (the A factor) of barkinite shows that barkinite can be inferred to be a type I kerogen and that barkinite has good hydrocarbon-generating potential.