Investigation of the Chemical Structure of Coal by Nuclear Magnetic Resonance and Infrared Spectrometry

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Abstract
The distributions of hydrogen and carbon among various organic structures in solvent extracts of selected coals have been determined by high-resolution proton and carbon-13 magnetic resonance spectrometry. Structural parameters including the aromaticity, the degree of aromatic ring substitution, and the average size of the condensed aromatic ring system have been deduced for each extract using the nuclear magnetic resonance data in conjunction with the elemental analysis of the material. Complementary infrared spectral studies of the extracts and their parent coals have been used to estimate the aromaticities of whole coals. The potential of two other magnetic resonance techniques, proton-enhanced nuclear induction spectroscopy and proton-decoupled high-resolution carbon-13 magnetic resonance, in coal research is discussed. The results of the present investigation are in accord with commonly held views of coal metamorphism; they do not, however, support recent reports challenging the classical view that coals arc highly aromatic materials.