Hydrogenation mechanism of coal tar pitch for carbon fiber. (Part 1). Estimation of hydrogen mobility of coal tar pitch for high performance carbon fiber using tritium tracer methods.

Abstract

Behavior of hydrogen in hydrogenation reaction of the coal tar pitch for high performance carbon fiber (HPCF), mesophase pitch based carbon fiber, was investigated using a tritium tracer technique to elucidate the hydrogenation mechanism. The coal tar pitch was hydrogenated by tritium labelled gaseous hydrogen without vehicle solvent nor catalyst. The hydrogenation of the coal tar pitch proceeded along first-order reaction with respect to partial pressure of hydrogen in gas phase. The activation energies of hydrogen addition and exchange were 9.7 and 16.2kcal/mol, respectively. At 300 and 350°C, hydrocracking of pitch radicals preceded the polycondensation of those to form larger amounts of light fractions such as HS and HIS-BS as compared to that of heavy ones such as BIS-THFS and THFIS. On the contrary, at 400°C, formation of the heavy composition increased. It was suggested that polycondensation of pitch radicals would be of greater advantage than hydrocracking of the same at 400°C.