INSITU MONITORING FOR MESOPHASE FORMATION PROCESSES OF VARIOUS PITCHES BY MEANS OF HIGH-TEMPERATURE C-13-NMR

High-temperature heating processes for coal-tar-derived (pitch A), petroleum-derived pitch (pitch B), and hydrogenated petroleum-derived pitch (pitch C) have been studied by in-situ high-temperature C-13-NMR. Mesophase formation processes have been successfully monitored for all three kinds of pitches. The times required for appearance of mesophase in pitches A and B are similar and shorter than that in pitch C at 430-degrees-C. Time intervals from mesophase appearance to finishing mesophase transformation in pitches B and C are nearly the same and shorter than that in pitch A at 430-degrees-C. There may be a critical region of aliphatic carbon content for mesophase appearance of petroleum-derived pitch. Completion of mesophase development correlates to the line-width of characteristic peak of 180 ppm assigned as carbon in stacked aromatic layer molecules. Aliphatic carbons of molecules in mesophase seem to cause an increase of mesophase mobility and a narrowing of the characteristic peak for mesophase around 180 ppm.