Chemical composition of SCG extracts obtained from coal and maceral concentrates

Five Turkish coals and macerals were subjected to supercritical toluene extraction at 400°C and 100 atm. The extracts were separated into three fractions, namely preasphaltene, asphaltene and oil. Oil fractions were further separated into paraffinic, aromatic and polar sub-fractions. This paper discusses the spectroscopic and chromatographic analysis of these paraffinic, aromatic and polar sub-fractions obtained from the supercritical extraction of whole coals and of their corresponding maceral concentrates

Supercritical toluene extraction of maceral concentrates obtained from Turkish coals

Five Turkish coals of rank varying from high volatile bituminous to sub-bituminous C were separated into four fractions by sequential sink-float treatment with cesium chloride solutions of different densities. Following the maceral analysis, each fraction was subjected to supercritical toluene extraction at 400°C and 100 atm. The extracts were separated into three fractions, namely preasphaltene, asphaltene and oil. Oil fractions were further separated into paraffinic, aromatic and polar sub-fractions. It is observed that SCG toluene extraction produces higher extract yields in lighter maceral concentrates when compared with those obtained from denser fractions. The average molecular weights of the extracts obtained from coals and from their corresponding maceral concentrates are all coal specific. The average molecular weights of the SCG extracts indicated that retrogressive reactions during SCG extractions are more prominent in low-rank coals. The oil fractions are dominating in the SCG toluene extracts and this is more prominent in the extracts obtained from sub-bituminous coals. The gaseous product formations during SCG extraction of the whole sub-bituminous coals are substantial but this is remarkably reduced during the SCG extraction of the corresponding maceral concentrates. © 1993