Thermoanalytical studies of pitch pyrolysis

Characterization of pitches by thermal analysis techniques is highly relevant to the practical use of these materials, as they undergo heat treatments in all of their utilization processes. The aim of this work was to improve the interpretation of the complex DTA curves of pitches by comparison with model compounds. For this, TG/DTG/DTA was used to study under identical conditions the pyrolysis of a petroleum pitch and a coal tar pitch as well as a number of polycyclic aromatic hydrocarbons. Results were interpreted as a function of the molecular structure, pyrolysis reactivity and graphitizability of cokes from the hydrocarbons. It is concluded that condensation and polymerization, which are the most likely exothermal reactions predominant in petroleum pitches, indicate the presence therein of reactive molecules. Alternatively, endothermal phenomena such as distillation, depolymerization and cracking, predominant in coal tar pitches, suggest the presence of light, little reactive aromatic molecules.Financial support from DGICYT (project PB87-0456) is gratefully acknowledged.