CHEMICAL STRUCTURAL FEATURES OF PYRIDINE EXTRACTS AND RESIDUES OF THE ARGONNE PREMIUM COALS USING SOLID-STATE C-13 NMR-SPECTROSCOPY

Soxhlet extractions were performed on the eight Argonne Premium coals using pyridine purged with argon and followed by a novel washing procedure to remove the pyridine. Mass closure (extracts plus residues) on duplicate experiments accounted for 94-96% of the original coal, repeatable to within 2%. Chemical structural features determined from C-13 NMR analyses of the extracts and residues showed more attachments per aromatic cluster for the residues, indicating a greater degree of covalent bonding in the residue than in the extract. H-1 NMR analysis of the extracts showed a gradual increase in the hydrogen aromaticity with rank, along with a maximum in the percentage of a-hydrogen in the high-volatile bituminous coals. Composite chemical features constructed from weighted averages of the features of the residues and extracts agree with many of the features of the parent coal. Chemical structural features of the extracts determined from H-1 NMR analyses agree with similar data reported previously for early coal tars during devolatilization at rapid heating rates.