Abstract
The relation between the nature of solvent and the extent of coal liquefaction has been studied by using liquid product as a recycle solvent. The whole product was separated into liquid and solid fraction by centrifugation and a part of the liquid fraction was used as a solvent for a continuous reaction. 80g of Taiheiyo-Coal, 100g of solvent and 5g of nickel-molybdenum-alumina catalyst were put into a 500ml stainless steel autoclave and were heated at 400°C for 1hr under hydrogen pressure. The total pressure was maintained at 250 kg/cm2 by means of introducing hydrogen gas through a pressure controller during the reaction. A hydrogenated anthracene oil was used as a starting solvent.
The coal conversion decreased gradually and the contents of asphaltene and preasphaltene in product oil increased during the passes, while the yield of liquid fraction by centrifugation decreased rather rapidly. The H/C values of asphaltene and preasphaltene were decreased during the passes, which indicate that an increase of heavy fractions in the recycle solvent causes a decrease of the catalytic activity for hydrogenation. The composition of distillate fraction has been analysed by means of gas chromatograph. Three-ring condenced-aromatics or more decreased and straightchain paraffins increased during the passes. The concentration of straight-chain paraffins in distillate fraction was reached about 30 wt% after five passes.
