COMPOSITION OF POTENTIAL OIL FROM HUMIC COALS IN RELATION TO THEIR PETROGRAPHIC NATURE

Previous studies of humic coals by Rock-Eval pyrolysis have shown that there is no correlation between the hydrogen index and the maceral composition. Moreover, the pyrolysis-BC analysis of the S//2 peak has shown that the pyrolysis products contain not only gaseous hydrocabons but also liquid hydrocarbons. To improve such studies, structural analyses were performed by liquid and gas chromatography of the pyrolysis products (C//1//5// plus fraction) from various humic coals having low to medium maturity. The polycyclic molecules in the C//2//5-C//3//5 range compounds were analyzed by GC-MS to determine the distribution of the tri-, tetra- and pentacyclic biomarkers. This distribution differs from one sample to another and the isomerization ratio of 'pyrolytic hopanes' appeared to be a possible parameter of rank. Such a diversity in the composition of the pyrolysate, independent of the age of the samples, is interpreted as resulting from the diversity of the genetic types of humic coals, a diversity which cannot be fully described by a bulk determination of their maceral composition.