SUPERCRITICAL TOLUENE EXTRACTION OF MACERAL CONCENTRATES OBTAINED FROM TURKISH COALS

Five Turkish coals of rank varying from high volatile bituminous to su b-bituminous C were separated into four fractions by sequential sink-f loat treatment with cesium chloride solutions of different densities. Following the maceral analysis, each fraction was subjected to supercr itical toluene extraction at 400 degrees C and 100 atm. The exacts wer e separated into three fractions, namely preasphaltene, asphaltene and oil. Oil fractions were further separated into paraffinic, aromatic a nd polar sub-fractions. It is observed that SCG toluene extraction pro duces higher extract yields in lighter maceral concentrates when compa red with those obtained from denser fractions. The average molecular w eights of the extracts obtained from coals and from their correspondin g maceral concentrates are all coal specific. The average molecular we ights of the SCG extracts indicated that retrogressive reactions durin g SCG extractions are more prominent in low-rank coals. The oil fracti ons are dominating in the SCG toluene extracts and this is more promin ent in the extracts obtained from sub-bituminous coals. The gaseous pr oduct formations during SCG extraction of the whole sub-bituminous coa ls are substantial but this is remarkably reduced during the SCG extra ction of the corresponding maceral concentrates.