Study On The Pyrolysis Condensation Of Coal-tar Pitch Used For Carbon Materials Manufacture

The processes of thermal weight loss of coal-tar pitch are studied by means of TGA. The characteristics of pyrolysis condensation of coal-tar pitch are analyzed. The character of pyrolysis condensation of medium pitch is compared with that of modified pitch. The influences of heating rate on the pyrolysis condensation of coal-tar pitches are investigated. It is found that rapid heating results in more constituents of coal-tar pitches evolving and is unfavourable to the enhancement of coking value of coal-tar pitches.According to the characteristics of the pyrolysis condensation reactions, the DAEM and Coats-Redfern models of pyrolysis reaction kinetics of coal-tar pitches have been established. The model expressions are as follow:Under different volatile conversion rates of coal-tar pitches, ln(h/T~2) in correlation curve is correlated with 1/T very well. It is found that the pyrolysis of coal-tar pitches are first order reaction.According to DAEM model calculation, the activated energies of pyrolysis reactions of medium pitch and modified pitch are 75～127kJ/mol and 60～140 kJ/mol separately. The activated energies of pyrolysis reactions of coal-tar pitches increase with the upgrade of volatile conversion rates.In first stage of pyrolysis, the activated energies of pyrolysis reactions of coal-tar pitches increase slowly. The activated energy of medium pitch pyrolysis is higher than that of modified pitch pyrolysis. In second stage of pyrolysis, the activated energies of pyrolysis reactions of coal-tar pitches increase drastically. The activated energy of medium pitch pyrolysis is lower than that of modified pitch pyrolysis.According to Coats-Redfern model calculation, the activated energies of pyrolysis reactions of medium pitch and modified pitch are 31～38kJ/mol and 29～39 kJ/mol separately. With increment of temperature rising rate, the activated energies of pyrolysis reactions of coal-tar pitches increase.