Extraction of coal below 350 degrees C in flowing non-polar solvent

Eight Argonne premium coals and an Australian brown coal (Morwell) were ext racted in a flowing stream of either tetralin or 1-methylnaphthalene under 10 MPa at 200-400 degreesC to examine the dissolution/depolymerization beha vior of coal in liquid phase. The flowing solvent was used to minimize the secondary interaction between the extract and the macromolecular network of coal. Four bituminous coals were extracted with negligible decomposition b elow 350 degreesC. The extract yield reached 65-80% for the bituminous coal s at 350 degreesC, and the extract was separated into about 25-40% of solub le fraction at room temperature (soluble) and about 40% of solid precipitat ed at room temperature (deposit). The detailed analyses of the soluble, the deposit and the residue through ultimate analysis, C-13 solid NMR, GPC, an d matrix-assisted laser desorption/ionization time-of-flight mass spectrome try (MALDI-TOFMS) enabled to examine the structure of Pittsburgh #8 (PITT) in detail. The raw PITT coal was found to contain small molecules (M-w = 13 0-600) and large molecules (M-w = 1300-3500) in its network. The soluble co nsisted of only small molecules, but both small and large molecules were in volved in the deposit and the residue. The extraction method employed in this work was found to be effective to se parate coal into different molecule size fractions without decomposition fo r bituminous coals. The soluble, being obtained in 20-40% yield and consist ing of molecules smaller than 600 of M-w, and the deposit, being obtained i n 40% yield at maximum and containing little ash, would be well utilized as either clean fuel or raw materials for the subsequent conversion. (C) 2001 Published by Elsevier Science Ltd.