Aromatic biomarker from brown coal, Sangatta coalfield, East Borneo of middle miocene to late miocene age

A section of the Sangatta coalfield in the Balikpapan formation located in Kutai Basin, East Borneo, Indonesia, is the Inul area, located North of Pinang Dome. This section of the coalmine has coals with low calories (ca. 4379 cal/g), which is why they cannot be used optimally yet. The reasons of using low calorie coals are besides from being used as a mixing ingredient for the blending process of high calorie coals, they are also used to diversify the coals through the process of coal liquefaction (coal to liquid). In order for the coal liquefaction to be processed correctly, there needs to be a study on the geochemistry organics through coal biomarker analysis, particularly on the hydrocarbon aromatic fractions, so that the origins of the coal organic compounds could be known. Biomarker analysis on the aromatic hydrocarbon fraction shows the existence of naphthalene compound groups with sesquiterpenoids skeleton, phenanthrene with diterpenoids, sesterpenoids skeleton and triterpenoids aromatic pentacyclic. The existence of cadalene compound, triterpene pentacyclic monoaromatic, -triaromatic, -tetraaromatic, -pentaaromatic and triterpenoid C-ring cleaved hydrocarbon with oleanane, ursane and lupane skeletons indicated that the source of coal organic compounds were derived from b-amyrin which were produced by Angiospermae plants. The coal biomarkers distribution, particularly the high abundance of triterpenoid pentacyclic triaromatic compound, confirmed the low maturity of the coals which is predicted to profit from the process of liquefaction due to the high contents of their aromatic fractions.