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N. М. Galashina, Р. M. Nedorezova, V. I. Tsvetkova, А. N. Klyamkina, F. S. D’yachkovskii, N. S. Enikilopyan


Particular features of stereospecific propylene polymerization in the presence of Ziegler-Natta catalysts deposited on graphite surface


Polimery 1989, No 6-7, 283




DOI: dx.doi.org/10.14314/polimery.1989.283


Summary

To explain the effect of support type and conditions of TiCl3-phase formation in Ziegler-Nątta catalysts, the activity and stereospecifity of TiCl4-Et2AlCl systems deposited on the surface of various supports (PE, PP, pearlite, graphite) have been determined. It has been found that a particularly high activity has catalyst deposited on graphite with crystallographic structure similar to that of violett-form of TiCl3. This catalyst is also characterized by a high stereospecifity. Evidence has been presented that the simultaneous occurrence of these two positive features of catalyst is due to the formation on the graphite support not of a linear (β-form of TiCl3, but of a laminar structure similar to that of α-, γ-. or δ-form of TiCl3. Moreover, the modifying effect of the chemical structure of graphite surface on the chain-growth active centres has been found. On the basis of the presented experimental data it could be concluded that an increase in the activity and stereospecifity of catalysts deposited on graphite surface results from the simultaneous effect of both the laminar structure of graphite and from the presence on its surface of aromatic rings with substituted atoms, which can play the role of electron donors and thus modify the structure of chain-growth active centres.


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