Ethylene Polymerization over Homogeneous Bis(imino)pyridine Vanadium Catalysts: Data on the Number and Reactivity of Active Sites Full article
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Journal of Polymer Research
ISSN: 1022-9760 , E-ISSN: 1572-8935 |
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| Output data | Year: 2012, Volume: 19, Number: 11, Pages: 9998 Pages count : 9 DOI: 10.1007/s10965-012-9998-y | ||
| Tags | Activation energy, Ethylene polymerization catalysts, Kinetics, Number of active centers, Propagation rate constants, Vanadiumcomplexes | ||
| Authors |
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| Affiliations |
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Funding (1)
| 1 | Russian Foundation for Basic Research | 07-03-00311 |
Abstract:
Method of polymerization quenching with radioactive carbon monoxide (14СО) has been used to determine the number of active centers (С P ) and propagation rate constants (k P ) for ethylene polymerization over the homogeneous catalysts 2,6-R2LVCl3+MAO (L: 2,6-(C6H3N=CMe)2C5H3N, R=Me, Et). For both catalysts the maximum number of active centers at 60 °C was found to be 0.42–0.50 mol molV −1 and the k P values—(16.4–20.0) × 103 L mol−1 s−1. It has been shown that noticeable decrease in the catalysts activity with polymerization time results from the decrease in the active centers number and simultaneous transformation of some part of the initial centers into a new ones with lower reactivity. Analysis of the С P and k P values, measured at different polymerization times, together with the values of the polyethylene molecular-weight distribution, allowed to calculate the content of the active centers of both types and the k P values of these centers. For the 2,6-Et2LVCl3+МАО catalyst, the effect of polymerization temperature on the С P and k P values has been studied. It has been found that with polymerization temperature growth from 25 to 60 °С, the С P value substantially increases. As a result, the value of the effective activation energy (E eff = 22.6 kcal mol−1) noticeably exceeded that of the activation energy of propagation reaction (E P = 14.2 kcal mol−1). It is proposed that the reason for the unusually high E P value is formation of “dormant” sites with vanadium-polymer bond at lower polymerization temperature.
Cite:
Barabanov A.
, Semikolenova N.V.
, Bukatov G.D.
, Matsko M.A.
, Zakharov V.A.
Ethylene Polymerization over Homogeneous Bis(imino)pyridine Vanadium Catalysts: Data on the Number and Reactivity of Active Sites
Journal of Polymer Research. 2012. V.19. N11. P.9998. DOI: 10.1007/s10965-012-9998-y WOS Scopus РИНЦ ANCAN OpenAlex
Ethylene Polymerization over Homogeneous Bis(imino)pyridine Vanadium Catalysts: Data on the Number and Reactivity of Active Sites
Journal of Polymer Research. 2012. V.19. N11. P.9998. DOI: 10.1007/s10965-012-9998-y WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | May 22, 2012 |
| Accepted: | Oct 8, 2012 |
| Published online: | Oct 16, 2012 |
| Published print: | Nov 1, 2012 |
Identifiers:
| Web of science: | WOS:000311672600021 |
| Scopus: | 2-s2.0-84867300889 |
| Elibrary: | 20491383 |
| Chemical Abstracts: | 2012:1659186 |
| Chemical Abstracts (print): | 158:216366 |
| OpenAlex: | W2042129976 |