The effects of temperature and density on the characteristics of the extracts from SCFE of a high-ash Brazilian coal

The effects of extraction temperature and density on the characteristics of the extracts from supercritical fluid extraction (SCFE) of a high-ash Brazilian coal, with toluene as primary solvent, were experimentally investigated. The influence of addition of 5 mol% ethanol on the characteristics of the extracts was also studied. The experimental conditions ranged from 593 to 673 K and 4.7 to 11.5 MPa in a semi-batch, laboratory-scale unit with a high-ash subbituminous coal, 0.85-1.18 mm particle size. The extracts were fractionated by preparative liquid chromatography into eight distinct chemical classes: saturated hydrocarbons (HC), monoaromatics, diaromatics, triaromatics, polycyclic aromatics, resins, asphaltenes and asphaltols. This method is shown to be an appropriate procedure for analysing the effects of the said process variables on the characteristics of the extracts, allowing the maximization of specific chemical fractions. The amount of lighter components in the extracts was observed to increase with increasing temperature and with addition of 5 mol% ethanol. The opposite trend was found with increasing solvent density, at constant temperature. Copyright (C) 1996 Elsevier Science Ltd.