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 t emperature (275-325 degrees C), reaction time (0-20 h) and air flow (60-120 l h(-1)) on pitch composition and properties were monitored by elemental a nalysis, solubility measurements and Fourier transform infrared spectroscop y. Pyrolysis behaviour of parent tar and resultant pitches was studied by t hermogravimetric analysis thermogravimetric/derivative-thermogravimetric (T G/DTG) curve and polarized-light microscopy. The development of mesophase w as monitored in the resultant pitches by optical microscopy of their pyroly sis products obtained at 450 degrees C. Results show that air-blowing of ta r, 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. (C) 1998 Elsevier Science Ltd. All rights reserved.