Structural Characteristics of Coal Tar-derived Isotropic Pitches and Their Soluble Fractions

摘要

Three coal tar-derived isotropic pitches obtained by air blowing reaction and two parent pitches obtained by vacuum distillation were extracted with benzene and carbon disulfide respecively. The hydrogen distribution of the soluble fractions was assessed by infrared spectroscopy (IR) and ~1H-NMR. Between the respective results of soluble fractions by two analytical techniques, reasonable agreement and good correlation were obtained. A method developed by the authors for the determination of the aromaticity index based on IR spectroscopy was found more reliable than ~(13)C-NMR method to differentiate the aromatic protion from the aliphatic portion in the pitches. Average structural parameters of CS_2 solubles of the three air blown pitches indicated the substantial differences in molecular size and shape. The 002-band of X-ray diffraction (XRD) clearly indicated the existence of stacking of aromatic planes in the three air blown pitches at room temperature. Analyses of IR and XRD profiles on the whole pitches suggested that three air blown pitches are different in aromaticity and crystallinity, although their softening points, H/C ratios. and solubilities are almost the same.