Pyrolysis behaviour of pitches modified with different additives

The wetting properties of a petroleum pitch were improved by adding three additives from the fine chemical industry in different proportions. The effect of the additives on the subsequent pyrolysis behaviour of the pitches was studied by thermogravimetric analysis and optical microscopy. The results show that the additives modify the TG/DTG profiles of the pitches and increase the carbonaceous residue at 1000 °C. This suggests that there is interaction between pitch/additive components during pyrolysis. The examination and quantification of the different mesophase features (single spheres, domains and mosaics) in the pyrolysis products obtained from the pitches at 430 °C corroborates the concurrence of interactions. The additive consisting of alkyl/carbonyl derivatives (additive B) and the additive composed of alkyl/sulphur derivatives (additive C) accelerate the formation of mesophase without altering the mechanisms of mesophase growth. On the other hand, the additive that is made up of a light fraction of esters and a heavy fraction of phosphorous derivatives (additive A) affects both the kinetics and mechanisms of mesophase development. The cokes obtained at 900 °C clearly reflect the changes produced in the pyrolysis products at 430 °C by the additives.