EXTRACTION AND SWELLING OF LOW-RANK COALS WITH VARIOUS SOLVENTS AT ROOM-TEMPERATURE

Low-rank coals were extracted with various solvents under ultrasonicat ion at room temperature. In the case of single solvent extraction, N-m ethyl-2-pyrrolidinone (NMP) gave the highest extraction yield for Loy Yang coal, 14.3 wt % (daf). Among the mixed solvents used in this stud y, NMP-methanol (8:2) and NMP-water (3:1) mixed solvents gave the high yields, 15.3 and 15.1 wt % (daf), respectively. The NMP-carbon disulf ide mixed solvent was not effective, although it gave very high extrac tion yields for bituminous coals. FT-IR measurements for Loy Yang coal , its extract, and residue showed that they have similar chemical stru ctures. In polar solvents, Loy Yang coal swelled more highly than subb ituminous coals, and the highest swelling ratio was also obtained in N MP, indicating high affinity between Loy Yang coal and NMP. The mixtur e of Loy Yang coal with NMP forms a gel structure at the composition o f about 83 wt % NMP and 17 wt % coal.