Proton Donor Quality Index (PDQI) was calculated from the chemical structural analyses by means of GC-LVEI MS for an SRC-II heavy distillate and twelve hydrogenated coal liquids derived from it. Evaluation of hydrogen donor ability of the liquids was attempted. PDQI increased with increasing severity of hydrogenation at the temperature less than 420°C, but PDQI decreased over 430°C. PDQI at 460°C became smaller than that of SRC-II heavy distillate.
Liquefaction experiments with Akabira coal were carried out using the liquids as solvent. It was found that the coal conversions increased with the increase of PDQI of the solvents. Multi regression analyses between the coal conversions and PDQI of the chemical species in the solvents were performed, and the role of the species for the coal conversions was estimated. And then, a relationship between benzene soluble conversions and PDQIs fitted by those results in the experiments of Akabira coal liquefaction with recycling solvents was discussed.