The role of carbon black/coal-tar pitch interactions in the early stage of carbonization

This study was undertaken to gain further insight into the types of interaction between pitch and carbon black (CB) occurring during thermal treatment in the initial stages of carbonization, and the effects on subsequent coke structure. A commercial coal-tar pitch was blended with CB and then thermally treated at temperatures between 400-450°C, for 5 hours - except for 430°C, where the time of treatment was for 10 hours. The same thermal treatments were applied in the absence of CB to test the effects of temperature alone. Parent and treated pitches were characterized by elemental analysis, optical microscopy, thermomechanical analysis (TMA) and sequential solvent extraction. Additionally, some of the fractions were characterized by FTIR, GC and ¹H-NMR. Cokes obtained at 900°C were characterized by optical microscopy in terms of their porosity and optical texture. Results show that the type of CB/pitch interactions are temperature dependent, these interactions being more significant at lower temperatures (below 425°C). Hydrogenation and polymerization reactions have successively occurred along the range of temperatures used. CB produced an increase of pitch carbon yield without affecting pitch fluidity at the lower temperatures. The effect on the reduction of coke porosity was pronounced at the initial stages of the treatment. Coke optical texture was also affected by the presence of CB showing smaller sizes.