QUANTIFICATION BY IN-SITU H-1-NMR OF THE CONTRIBUTIONS FROM PYRIDINE-EXTRACTABLES AND METAPLAST TO THE GENERATION OF COAL PLASTICITY

High-temperature H-1 n.m.r. measurements were made on four Australian bituminous coals and their pyridine extracts and residues to quantify the contributions from the extractable material and fluid material gen erated by thermolytic reactions (metaplast) to the overall development of fluidity. Solid-state C-13 n.m.r. and e.s.r. indicated that the py ridine-extractables are less aromatic than the parent coals and contai n lower concentrations of free radicals. Although the pyridine-insolub les did not soften appreciably up to 550 degrees C, some partly fluid material was discernible at the temperature of maximum fluidity and, f or the good coking coals, this accounted for between one-third and one -half of the fluid phase generated. Although the pyridine-extractables softened at temperatures as low as 150 degrees C, giving halfwidths o f only similar to 1.2 kHz, they still did not soften completely at max imum fluidity (25% rigid material). Taking the separate contributions from the pyridine-extractables and residues for the whole coals, the p redicted proportions of the total hydrogen in the fluid phase at maxim um fluidity were in close agreement with these observed. Further, the predicted spin-spin relaxation times from the two separate contributio ns were also close to those observed. Thus the pyridine-extractables d o not appear to increase markedly the amount of metaplast generated; t hey serve mainly to increase the mobility of the fluid phase. (C) 1997 Elsevier Science Ltd.