Fuel, Vol.77, No.11, 1237-1241, 1998
Investigation of extracts of coal by supercritical extraction
Supercritical extraction of Leping coal was isothermally carried out with toluene and its co-solvent at 355-425 degrees C/ 5-10 MPa in a semi-continuous apparatus. The results indicated that extraction conditions affected the elemental composition, thermogravimetric characteristics and group components of extracts and their fractions. The yield of extract at 380 degrees C with toluene reached a maximum 64 wt% (in daf coal) containing 31 wt% oil which included aliphatics 22 wt%, aromatics 20 wt% and polar compounds 39 wt%. H/C atomic ratio of oil in such an extract was 1.38 and its weight loss at 300 degrees C was 30%. Analysis of i.r. and H-1-n.m.r. spectra was employed to characterize the coal extract and its fractions.