Carbonization and liquid-crystal (mesophase) development. 9. The co-carbonization of vitrains with Ashland A200 petroleum pitch

Vitrains from a wide range of ranks of coals were carbonized singly and also co-carbonized (HTT 1273 K) with 25% of Ashland A200 petroleum pitch. Polished surfaces of the resultant cokes were examined for optical texture in a polarizing-light optical microscope using a half-wave retarder plate to produce interference colours. For the anthracites, there is no modification of either component during co-carbonization. The growth of optical texture from the A200 pitch is not affected. For all caking vitrains the optical texture of coke from the blend system is extensively modified when compared to the optical texture of coke from the vitrain. For the low-rank non-caking vitrains the isotropic coke becomes totally or partially anisotropic in co-carbonization. The mechanism of modification of the optical texture of resultant cokes is related to the formation of nematic liquid crystals, mesophase and the semi-coke. It is not considered that the chemistry of pyrolysis is modified on cocarbonization of the vitrain and pitch.