Preparation of novel pitches by tar air-blowing

This study is concerned with the preparation of high carbon yield coal-tar pitches by tar air-blowing under pressure (0.5 MPa). The influence of the temperature (275–325°C), reaction time (0–20 h) and air flow (60–120 l h−1) on pitch composition and properties were monitored by elemental analysis, solubility measurements and Fourier transform infrared spectroscopy. Pyrolysis behaviour of parent tar and resultant pitches was studied by thermogravimetric analysis thermogravimetric/derivative-thermogravimetric (TG/DTG) curve and polarized-light microscopy. The development of mesophase was monitored in the resultant pitches by optical microscopy of their pyrolysis products obtained at 450°C. Results show that air-blowing of tar, performed under mild conditions, promotes the condensation of molecular components producing cross-linked oligomers, so increasing the yield of the process. The extent of polymerization increased with severity of treatment and resulted in an increase of pitch carbon yield. Moreover, the different properties of prepared pitches offer the possibility to obtain cokes with a wide range of optical textures.