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K. Czaja


Deactivation of complex organometallic catalysis


Polimery 1993, No 8-9, 380


DOI: dx.doi.org/10.14314/polimery.1993.380

Summary

The mechanism of the deactivation process of organomctallic catalysts in the process of suspension polymerization of ethylene was investigated. Conventional catalysts of the type of [Ti(OR)nCl4.n + EtmAlCl3.m] as well as catalysts immobilized on a carrier (such as various types of aluminagcl: [А12О3/ТЮ4 + Et2AlCI]} or on a complex magnesium carrier: [MgCl2(THF)2/TiCI4 + Et2AICl] were studied. It was found that the deactivation rate of organomctallic active centres can be described by a first order equation. Both ethylene and hydrogen (introduced as molecular-weight controlling agent) do not play an important role in the process of catalyst deactivation. It was established that the reason of deactivation of many organomctallic catalysts, mainly those without carrier, is the interaction of the organoaluminium component of the catalytic system with the titanium active centre. This component deactivates catalyst by reducing active Ti(III) to inactive Ti(II) and, above all, by poisoning active centres via blocking free coordination sites at titanium atom. The relative participation of these two processes and catalyst stability depend largely on the catalyst structure and morphology.


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