The effects of microwave receptor to coal (receptor/coal) ratio and the period of heating by microwave energy on the solubilization of Turkish coals in tetralin have been investigated. CuO was used as microwave receptor. The amount of receptor and the type of coal significantly affected the yield of liquid product. The addition of the CuO receptor caused to increase in the lignite conversions to oil fractions. The yield of THF soluble fraction increased in the presence of CuO receptor, however, due to catalytic effect of CuO, the yields of preasphaltene (PAS) and asphaltene (AS) decreased. The oil fractions were obtained from the experiments treated by microwave energy in the presence of 3/5 CuO/coal ratio and in the absence of receptor for 20 min liquefaction periods. The compositions of the oil fractions were determined by GC/MS. The composition of the oil fractions of the coals strongly depends on the type of coal. It was observed that the oil fractions contain oxygenated aromatic compounds in addition to condensed aromatic structures. Considerable amounts of 3,4-dihydro-1(2H)-naphthalenone (alpha-tetralone) were found in the oil fractions of lignites treated by microwave energy. (C) 2008 Elsevier Ltd. All rights reserved.