Mobilization of the Hydroxyls in a Brown Coal with Solvent-Induced Swelling Evaluated by Pulsed 1H NMR

Abstract

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/benzene-d6 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 the 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 pola...