Hydrogenation Mechanism of Coal Tar Pitch for Carbon Fiber(Part 3). Effects of Hydrotreatment on Pyrolysis Reactivity of Each Component in Coal Tar Pitch for High Performance Carbon Fiber.

Abstract

Coal tar pitch for high performance carbon fiber (HPCF) was hydrotreated using tritium labelled tetralin as donor solvent at 450°C for 120min. The hydrogen transfer in this process was determined quantitatively according to results obtained from radioisotope tracer method. The hydrotreatment of pitches can be explained by a general mechanism such as involved in the hydrotreatment of petroleum heavy oil or coal liquefaction. The tritiated pitch was heat-treated in the range of 30 to 1, 000°C under nitrogen atmosphere. It was found that the reaction of carbon-carbon bond cleavage and the evaporation of volatile components were basically completed at about 600°C. The dehydrogenation of polynuclear aromatic rings was sustained up to 1, 000°C. The model based on the first order rate expression was able to analyse TGA data successfully. Activation energies and frequency factors, for the nonisothermal heat treatment of pitches and each component of pitches, were calculated. The pyrolysis activation energies of the pitch and major components (HIS-BS and BIS-THFS fractions) in the pitch decreased when the pitch was hydrotreated.