Structural characteristics of coal tar-derived isotropic pitches and theirsoluble fractions

Three coal tar-derived isotropic pitches obtained by air blowing reaction a nd two parent pitches obtained by vacuum distillation were extracted with b enzene and carbon disulfide respectively. The hydrogen distribution of the soluble fractions was assessed by infrared spectroscopy (IR) and H-1-NMR. B etween the respective results of soluble fractions by two analytical techni ques, reasonable agreement and good correlation were obtained. A method dev eloped by the authors for the determination of the aromaticity index based on IR spectroscopy was found more reliable than C-13-NMR method to differen tiate the aromatic portion from the aliphatic portion in the pitches. Avera ge structural parameters of CS2 solubles of the three air blown pitches ind icated the substantial differences in molecular size and shape. The 002-ban d of X-ray diffraction (XRD) clearly indicated the existence of stacking of aromatic planes in the three air blown pitches at room temperature. Analys es of IR and XRD profiles on the whole pitches suggested that three air blo wn pitches are different in aromaticity and crystallinity, although their s oftening points, H/C ratios, and solubilities are almost the same.