Comparative evaluation of mesophase pitches derived from coal tar and FCC-DO

Abstract

Three kinds of mesophase pitches (MPs) derived from FCC-DO (P) and hydrogenated QI free coal tar (QIF) were comparatively evaluated in terms of their spinnability and stabilization reactivity based upon their structural characterizations. MP-P, which is meso-phase pitch from FCC-DO, preserved considerable amount of aliphatic and naphthenic hydrogens to show higher solubility, fusibility and softening temperature of as low as 245 °C in spite of its complete anisotropy. MP-C1 derived from catalytically hydrogenated QIF carried less hydrogen content and smaller molecular weight although its solubility and softening temperature were almost the same to those of MP-P. MP-C2 which was prepared from QIF treated with tetrahydro-quinoline (THQ) showed the least hydrogen content, the lowest solubility and the highest softening temperature of 290 °C. MP-P allowed smooth spinning for much longer time at the temperature from 320 to 350 °C. MP-C1 could be spun at the temperature from 340 to 370 °C, which was much higher than that of MP-P in spite of their similar softening temperatures. MP-C2 showed spinnability at the temperature from 340 to 390 °C, although evolved gases disturbed its smooth spinning at the higher temperature.

MP-P showed the highest stabilization reactivity to require the shortest time (120 min) for the sufficient stabilization at 250 °C. Although much longer time of 180 min was necessary for the MP-C1 at 250 °C, a higher temperature of 270 °C accelerated the stabilization reactions to shorten the time to 60 min. MP-C2 showed the least reactivity, requiring 120 min at 270 °C. More aliphatic and naphthenic structure of FCC-DO derived mesophase pitch is related to its superiority as the pitch fibre precursor. The catalytic hydrogenation which can produce naphthenic or aliphatic structure is a better pre-treatment to modify the coal tar as the mesophase pitch precursor.