Supercritical gas extraction of Taiheiyo coal has been investigated using toluene, toluene-tetralin mixtures, toluene-quinoline mixtures, and water as solvents with semi-batch type apparatus. Regardless of the solvents used, extraction yield and conversion increased with an increase in extraction pressure and reached a maximum at about 20 MPa. For toluene, a maximum in extraction yield occurred at a temperature around 350 degree C, and a nearly linear relation was observed between the conversions and temperature in the range of 330 to 380 degree C. Extraction of coal gave three products. The molecular structure of the coal extract became more condensed with increasing temperature, pressure and extraction time. The extraction mechanism could be explained using a two-component structure model.
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