SOLVENT-EXTRACTION OF COALS DURING ANALYTICAL SOLVENT SWELLING - A POTENTIAL SOURCE OF ERROR

Bruceton coal (Pittsburgh No. 8) was exhaustively extracted with pyridine, and the residue was swollen with toluene, chlorobenzene, and pyridine. The solvent volume used to swell a constant amount of coal was varied. The coal swelling in chlorobenzene and pyridine increased as the volume of the solvent used to swell the coal increased. Vapor pressure osmometry was used to measure the concentration of materials dissolved in the swelling solvents contacting the coal. Both chlorobenzene and pyridine extracted enough material from the coal residue to promote solvent activity and reduce solvent swelling. The concentration of extracted material decreased as the volume of the swelling solvent increased. The use of high solvent:coal ratios in solvent swelling experiments is recommended and long exposure of the coal to the solvent after equilibrium has been reached should be avoided.