Effect of pressure on the coking yields of coal tar pitches
Pyrolysis of five coal tar pitches with wide ranging characteristics, made from the same coal tar precursor, has been studied under nitrogen pressures of 105, 50×105, 90×105 and 160×105 Pa, at a temperature of 550 °C. The residues were further heat-treated to 900 °C to obtain the ultimate normal (105 Pa) and pressure coking yields of these pitches. The literature states that for pitches with relatively lower softening points the carbonization pressure not only increases the coking yield but also lowers the temperature at which the pyrolysis is complete. This is seen to hold true for the present set of pitches, having a much wider range of softening points. Further, one of the pitches, earlier reported by us to be a good preforming pitch for carbon-carbon composites, gave an ultimate coking yield of 88% on subjection to a nitrogen pressure of 160×105 Pa at 550 °C followed by ambient pressure carbonization to 900 °C. It thus appears that a carbonization pressure of 160×105 Pa for a suitable preforming pitch can act as a reasonably good alternative to the expensive hot isostatic pressure impregnation carbonization technique employed in the production of carbon-carbon composites.
KeywordsPolymer Pyrolysis Good Alternative Ambient Pressure Softening Point
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- 2.K. J. Huttinger and U. Rosenblatt, in Proceedings of the 4th Conference on Industrial Carbon and Graphite, London, 1974 (Society of Chemical Industry, London, 1976).Google Scholar
- 4.R. L. Burns and J. L. Cook, in “Pressure carbonisation of petroleum pitches”, Vol. 21, edited by M. L. Deviney and T. M. O'Grady (American Chemical Society, Washington, 1974), p. 139.Google Scholar
- 5.W. Chard, M. Conaway and D. Neisz, ibidin, p. 155.Google Scholar
- 6.W. L. Lachman, J. A. Crawford and L. E. McAllister, in Proceedings of the International Conference on Composite Materials, edited by B. Noton, R. Signorelli, K. Street and L. Phillips (Metallurgical Society of AIME, New York) 1978.Google Scholar
- 7.L. E. McAllister and W. L. Lachman, in “Hand-Book of Composites”, Vol. 4, edited by A. Kelly and S. T. Mileiko (Elsevier Science Publishers, B.V., 1983) pp. 109–175.Google Scholar
- 8.L. E. McAllister and R. L. Burns, in “Extended Abstracts — 16th Biennial Carbon Conference” (American Carbon Society, 1983) p. 478.Google Scholar
- 9.R. K. Aggarwal, G. Bhatia, O. P. Bahl and L. M. Manocha, in Proceedings of the Seminar and Workshop on Carbon Fibers and their Applications, New Delhi, 15–17 December 1986 (Indian Carbon Society, New Delhi, 1986) p. 151.Google Scholar
- 10.O. P. Bahl, L. M. Manocha, Y. K. Singh, G. Bhatia, R. K. Aggarwal and T. L. Dhami, in Proceedings of the International Carbon Conference, Baden-Baden, West Germany (German Ceramics Society, 1986) p. 738.Google Scholar
- 11.O. P. Bahl, L. M. Manocha, G. Bhatia and R. K. Aggarwal, Final Technical Report, DST-UNDP Project (1986).Google Scholar
- 12.O. P. Bahl, L. M. Manocha, G. Bhatia, T. L. Dhami, R. K. Aggarwal, and S. S. Hanspal, Final Technical Report (1986).Google Scholar
- 13.G. Bhatia, R. K. Aggarwal and O. P. Bahl, in Proceeding of the Indo-Japanese Workshop on Pitch and Pitch Based Products, New Delhi, November 24–25, 1989 (Indian Carbon Society, New Delhi) pp. 24–46.Google Scholar