Coals were heat-treated at heating rate of 3℃/min in an autoclave under nitrogen, and then quenched to room temperature. The heat-treated coals were extracted with a carbon disulfide-N-methyl-2-pyrrolidinone (CS_2-NMP) mixed solvent at room temperature. Molecular weight distribution (MWD) of the extracts (solvent-soluble-component) was investigated by the size exclusion chromatography (SEC) method using the CS_2-NMP mixed solvent as mobile phase. The extraction yields of the heat-treated coals gave a maximum in the softening range, and there was a good correlation between the maximum fluidity and the maximum extraction yield of the coals. Fluidity of heat-treated coals is discussed from the changes of MWD of the extracts.
