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2 Polish Journal of Chemical Technology

2 2001

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Modification of the properties and carbonization behaviour of coal tar pitches on progressive air-blowing

Machnikowski J., Gerus-Piasecka J., Kubica K., Machnikowska H.

Polish Journal of Chemical Technology

2001

Vol. 3, nr 1

7-14

Pitches with softening points of about 140°C, 175°C and 210°C were prepared by progressive air-blowing at 300°C of coal-tar pitches from different commercial coke-oven tars. The modification induced by the mild oxidation was monitored using solvent fractionation, elemental analysis and contact angle measurement. The kinetics and mechanism of mesophase formation on isothermal treatment at 450°C and the optical texture of resultant cokes were studied by polarized-light optical microscopy. The air-blowing increases gradually the coking yield and toluene insoluble content of pitch with very little changes in quinoline insoluble content and elemental composition. The modified pitches preserve characteristic structural features of parent materials. Air-blowing accelerates the formation of mesophase on carbonization and modifies to a different extent the mechanism of the transformation. QI particles tend to form large aggregates in the early stage of the transformation and mesophase growth occurs in the practically Ql-free pitch, leading to two-phase optical texture of resultant cokes.

High softening point pitches produced by air-blowing of Qi-free coal-tar derived precursors

Machnikowski J., Gerus-Piasecka I., Kubica K., Machnikowska H.

Polish Journal of Chemical Technology

2001

Vol. 3, nr 2

11-16

Modified pitches with the softening point of about 220°C were prepared by air-blowing at 300°C of Qi-free pitches from commercial "light" and "heavy" coke-oven tars. The effect of parent tar nature and Qi-free tar distillation conditions on air-blowing behaviour was studied using solvent and extrographic fractionation, elemental analysis, 1H NMR, and contact angle measurement. The kinetics and the mechanism of the mesophase formation on isothermal treatment at 450°C and the optical texture of semi-cokes were studied by polarized-light optical microscopy. Under these conditions totally isotropic pitches of considerably enhanced coking yield and TI content with very little change in elemental composition produced. The air-blowing accelerated the formation of mesophase on carbonization without marked affecting the mesophase units growth and the flow type optical texture of semicoke. The pitch from Qi-free "heavy" tar distilled under the reduced pressure was selected as most suitable potential precursor for isotropic carbon fibers.