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- Title
Mechanism of olefin polymerization on supported Ziegler-Natta catalysts based on data on the number of active centers and propagation rate constants.
- Authors
Bukatov, G.; Zakharov, V.; Barabanov, A.
- Abstract
The number of active centers (Cg) and propagation rate constants (kg) for the polymerization of propylene and ethylene on highly active titanium-magnesium catalysts (TMCs) of different compositions at 70°C were determined using the method of14CO inhibition of polymerization. In the polymerization of propylene on the TiCl4/D1/MgCl2-AlEt3/D2 system (D1 is dibutyl phthalate or 2,2'-diisobutyl-1,3-dimethoxypropane; D2 is a silane), the effects of D1 and D2 donors on the values ofCg andkg were studied. It was found that the donors decreased the values ofkg for nonstereospecific centers, had no effect on the values ofkg for stereospecific centers, and increased the fraction of stereospecific centers, as well as the fraction of “sleeping” centers regardless of their stereospecificity. The rate constants of isotactic-chain transfer with C3H6, AlEt3, H2,and ZnEt2 were determined. In the polymerization of ethylene, a number of TMCs exhibited strong diffusion limitations, which manifested themselves in a dramatic decrease in the determined values ofkg. It was demonstrated that diffusion limitations can be removed by decreasing the particle size and the concentration of active centers and by performing prepolymerization with propylene. The values ofkg in ethylene polymerization were similar for stereospecific and nonstereospecific centers.
- Subjects
POLYMERIZATION; CHEMICAL reactions; ZIEGLER-Natta catalysts; PROPENE; ETHYLENE; ALKENES
- Publication
Kinetics & Catalysis, 2005, Vol 46, Issue 2, p166
- ISSN
0023-1584
- Publication type
Article
- DOI
10.1007/s10975-005-0065-0