Extraction of coal-tar pitches with toluene near the critical point: gasification and coal hydrogenated pitches

The extraction of coal-tar pitches with toluene near the critical point was investigated using a laboratory-scale semi-batch extraction cell. Coal-tar pitches from processes using gasification and hydrogenation of coal to produce synthesis gas and liquid fuel products respectively was used. The effect of process variables on the properties of the extract and residue fractions was determined. It was found that the amount and number-average molecular weight of the extract and residue can be varied over a wide range by modest changes in temperature and pressure near the critical point of toluene. An analysis of selected samples of extract and residue fractions is given to demonstrate the use of extraction with toluene near the critical point for refining coal-tar pitches with vastly different properties. (C) 1999 Elsevier Science Ltd. All rights reserved.