Supercritical fluid extraction of a high-ash Brazilian mineral coal

The effects of extraction temperature, solvent density and addition of cosolvents on the conversion, liquid yield and also on the characteristics of the extracts and residues from SCFE with toluene of a high-ash Brazilian mineral coal were experimentally investigated (Rocha [1]). The experiments were performed in a semi-batch laboratory-scale unit in the coal pyrolysis region - 593 to 673 K and with pressures up to 11.5 MPa. It was observed a reduction in the total sulfur content up to 44%, whereas providing residues with maximum losses of 16% of the original heat-content. The extracts were characterized by a reliable, non-destructive Preparative Liquid Chromatography method - PLC-8 (Karam et al. [2]), providing eight discrete fractions with well defined chemical functionality. With the addition of 5 mol% tetralin 21.7% conversion was obtained, that means an increase of 15% when compared to pure toluene, while with n-methyl-2-pyrrolidone (NMP) and ethanol the conversion decreased.