SWELLING OF THE EXTRACTS AND RESIDUES FROM CARBON DISULFIDE-N-METHYL-2-PYRROLIDINONE MIXED-SOLVENT EXTRACTION

Solvent swellings of the raw coals, their extracts and residues, which were obtained by carbon disulfide-N-methyl-2-pyrrolidinone mixed solvent extractions of some bituminous coals at room temperature, were studied. The swelling ratios (Q) of the raw coals were generally lower than those of the corresponding extracts and residues, like the results of Larsen et al. for the swelling of two bituminous raw coals and their residues. Swelling ratios of PS (pyridine-soluble and acetone-insoluble extract fraction), PI (pyridine-insoluble extract fraction), and residue in four solvents were in the order of cyclohexane < methanol < benzene < THF for three bituminous coals. For Illinois No. 6 coal, which has a higher oxygen content than the coals above, swelling ratios in methanol are higher than those in benzene. Large synergistic effect for the swelling ratios of PI in benzene-methanol mixed solvent was observed. These results were discussed from the points of the nature of cross-link bonds and cross-link density of raw coals, extracts and residues.