| Abstract
| - In situ electron paramagnetic resonance (EPR) spectroscopy was used to investigate the behaviorof free radicals in a lignite Banko coal (%C: 71.3%) that was heated to 300 °C at a rate of 10°C/min in a hydrogen-donating solvent 1,4,5,8,9,10-hexahydroanthrancene (HHA), a polar solventN-methyl-2-pyrrolidinone (NMP), and mixtures of the two solvents (NMP/HHA). With HHA, theradical intensity increased slightly as temperature increased from 60 to 200 °C, and then decreasedgreatly as it increased to 300 °C, due to the stabilization of radicals by hydrogen transferredfrom HHA. In contrast, the radical intensity in NMP increased greatly from 60 °C to 260 °C andthen decreased slightly. NMP, an aprotic polar solvent, might interact with the free radicals andprevent the radical molecules from recombining and taking part in addition reactions. WhenNMP/HHA mixtures were used, changes in the radical intensity was dependent on the proportionof HHA. Moreover, the EPR spectra were deconvoluted to narrow and broad lines, and the behaviorof the broad-line components was found to be related to coal dissolution in HHA.
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