Two different types of isotropic coal tar pitch (CTP) were thermally treated to form mesophase pitch for the purpose of producing carbon fibers. One of the CTP samples readily formed mesophase spheres (GCTP) as expected after thermal treatment around 400 °C, whereas the other sample formed small dendritic domains of mesophase (BCTP). Neither sample contained any quinoline-insolubles, as these were removed prior to mesophase formation. Several chemical differences were observed between these two CTP samples. The elemental composition showed that the BCTP had six times the oxygen content than the other pitch and was less aromatic, which was confirmed by FTIR spectroscopy and various FTIR indices. Additional compositional differences in the materials was identified using the saturates, aromatics, resins-Asphaltene Determinator (SAR-AD) separation/fingerprinting method. When preparing these samples for this method, it was observed that the BCTP had significantly more chlorobenzene-insolubles. Furthermore, the SAR-AD analyzed chlorobenzene-soluble portion of BCTP contained significantly more saturates and &lt;4 ring aromatics and resins, whereas the GCTP was highly enriched in 4+ ring aromatics. Fluorescence emission spectra and synchronous fluorescence spectra also showed significant differences between the fused aromatic structures between the two materials.

Effect of chemical composition of coal tar pitches on mesophase formation and structure

2019 Spring National Meeting

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