Liquefaction of Gediz coal

49 SUMMARY In this study, the solvent and catalyst effects on the direct liquefaction of Gediz subbituminous coal from Uşak were investigated. Therefore at different temperatures, solvent and catalyst combinations, coal were liquefied in single and two stage reactions. Tetralin was used hydrogen donor, decalin as hydrogen shuttler and ammonium heptamolibdate as catalyst precurser. It was observed that Gediz coal was highly reactive due to its high pyrite and weak etheric bonds. At 400°C temperature total conversion of a 90% was obtained. Increase of reaction temperature caused an increase in conversion and lowered the molecular weight distribution. The use of tetralin as solvent increased the hydrogenation of radicals and prevented reverse reactions, there by advancing the formation of low molecular weight products. At 450°C temperature the use of tetralin provided 97% total conversion and a 67.2 yield of % oil+gas. AHM which becomes M0S2 during liquefaction depending on the reaction temperature and sulphur content of the coal, was also used in experiments. It was observed that the catalyst was effective.in the formation of AS and PAS. In the experiment without catalyst at 450°C temperature the oil+gas yield was 49.4%, this value decreased to 41% when the catalayst was used. The use of tetralin and catalyst together increased total conversion, oil yields and particularly AS yield. In the experiment with tetralin and without catalyst at 400°C, the AS yield was 32 %. This yield was 46% with catalysed coal. The use of tetralin increased the total conversion and yield of oil+gas, but decreased H2S formation. As a result, the sulphur content of the products increased. In experiments at 450"^Ç without catalyst and solvent, sulphur content of the oil fraction was 9.1%. This value increased to 27.4% when tetralin was used. In the experiments in which catalysed coal was used the sulphur content of oil was increased from 5.7% to 33.5 % by the use of tetralin. The reason for the increase in the sulphur contents of the products was thought to be secondary reactions between tetralin and H2S. Total conversion decreased from 81.9% to 74.6% in experiments performed without catalyst and decreased from 93.5% to 85.7% in experiments with catalyst when the reaction period was increased from 30 minutes to 60 minutes. Experiments in the absence of catalyst showed an 8% decrease. In two staged experiments the total conversion,the conversion to other producls, the formation of H2S increased. Two staged experiments with AHM and no solvent showed a 61.2% oil+gas yield having a 3.1% sulphur content. When tetralin was used in the second stage, the highest yield of oil+gas was is 71.5%. However, the sulphur content of the oil product was higher than in other two staged experiments (14.1%). In order to determine the effect of coal mineral matter, demineralized coals were liquefied at 400°C for 30 minutes. As a result, it was observed that pyrite catalysed total conversion and clays decreased total conversion. GC-MS analyses of liquid products (oil) showed that these products to contain straight chain hydrocarbons, there were also pristane andV.50 phytane isoprenoids in ail oil fractions from catalysed coal. Oil fractions also containing mono and dicyclic hydrocarbon structures substituted with alkyl groups. Such polyaromatic structures as anthracene, phenanthrene were obserbed in much higher quantities with increasing temperature and reaction period. By taking certain ion- range values such sulphur containing compounds as benzothiophene, dibenzothiophene and their alkyl substituents were determined.