The amount of hydroxylic hydrogen mobilized with the solvent-induced swelling of a brown coal was measured using a pulsed 1H NMR technique. Yallourn brown coal (YL), and deuterated YL (YL-d), prepared by selectively deuterating all the hydroxyls in YL, were swollen in binary solvents, including different pyridine-d5/benzene-d6 and dimethyl sulfoxide(DMSO)-d6/benzenerfe mixtures, at 303 K. The volumetric swelling ratio (Q) and the amount of mobile hydrogen were measured as a function of the composition of the solvent. The amount of hydroxylic hydrogen remaining immobile, fiM(OH), was also determined experimentally by comparing the amounts of mobile hydrogen in YL and YL-d. The fIM(OH) of YL in DMSO-benzene mixtures was found to be smaller than that in pyridine-benzene mixtures over thé entire range of Q from 1 to 3.5, demonstrating that DMSO reduces the hydrogen bonding associations between coal macromolecules more extensively than pyridine does for the swelling with equivalent Q. The effects of these polar .solvents on the relationship between fIM(OH) and Q can be attributed to the differences in their hydrogen bonding abilities.
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