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M. Białek, К. Czaja, M. Białoń



Verification of the kinetic model of ethylene polymerization over organovanadium catalysts deposited on a magnesium carrier


Polimery 1998, No 7-8, 422


DOI: dx.doi.org/10.14314/polimery.1998.422


Summary

The kinetic studies are reviewed on low-pressure polymerization of ethylene over two types of organovanadium catalysts, viz., MgCl2(THF)2/VCl4/Et2AlCl and MgCl2(THF)2/VOCl3/Et2AlCl, each deposited on a magnesium carrier. The polymerization rate was found to be directly related to the catalyst and monomer concentrations (Figs. 2 and 3), unless when the access of the monomer to the reactive V-C bond is restricted by diffusion. Polymer chain termination step was found to result from the reaction of the transfer onto the monomer and to be associated with the regeneration of the active site on which a new macromolecule can be formed. A kinetic model was developed for the ethylene polymerization process carried out over the catalysts examined. The model allows to calculate the concentration of active sites (C*), the transfer rate constant (ktr),and the propagation rate constant (kp) from the experimentally observed yield and molecular weight of polyethylene recorded in various polymerization times.


Keywords: organovanadium catalysts on carriers, polymerization of ethylene, mechanism of termination reaction, kinetic model of polymerization


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