Ethylene Polymerization over Homogeneous and Supported Catalysts Based on Bis(imino)pyridine Co(II) Complex: Data on the Number of Active Centers and Propagation Rate Constant Full article
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Macromolecular Chemistry and Physics
ISSN: 1022-1352 , E-ISSN: 1521-3935 |
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| Output data | Year: 2008, Volume: 209, Number: 24, Pages: 2510-2515 Pages count : 6 DOI: 10.1002/macp.200800376 | ||
| Tags | Bis(imino)pyridine Co catalysts, Molecular weight distribution, Number of active centers, Polyethylene, Propagation rate constant | ||
| Authors |
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| Affiliations |
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Funding (1)
| 1 | Russian Foundation for Basic Research | 07-03-00311 |
Abstract:
The number of active centers (Cp) and propagation rate constant (kp) for ethylene polymerization
with homogeneous catalyst LCoCl2 + MAO and supported catalyst LCoCl2/SiO2 + Al(iBu)3, where
L is 2,6-(2,6-(Me)2C6H3N = CMe)2C5H3N, have been determined using the method of polymerization quenching by radioactive carbon monoxide (14CO). The unstable rate profile of the reaction was attributed to a decrease in the number of active centers from 0.23 to 0.14 mol mol-1 (Co) corresponding to an increase in the reaction time from 5 to 15 min, whereas the kP value remained constant, amounting to 3.5 x 103 L mol-1 s at 35 oC. A narrow
molecular weight distribution of the obtained polyethylene (PE) samples (Mw/Mn= 1.9) testifies that the homogeneous catalyst LCoCl2 + MAO can be regarded as a single-site system. The activity of the supported catalyst was stable and noticeably lower than that of the homogeneous catalyst due to the low concentration of the active centers (0.02–0.03 mol mol-1 (Co)). PE with a broad molecular weight distribution (Mw/Mn = 36) and noticeably higher molecular weight is formed in the presence of the supported catalysts. The activity of the supported catalyst increases sharply at polymerization in the presence of hydrogen. The data obtained on the CP and kP values allow suggesting the formation of the ‘‘dormant’’ centers at polymerization without hydrogen
and regeneration of the active centers in the presence of hydrogen. The average kP values for the supported
catalyst containing multiple active centers were determined to be 5.9x 103 and 10.5 x 103 L mol-1 s, respectively, at 35 and 50 oC.
Cite:
Barabanov A.A.
, Bukatov G.D.
, Zakharov V.A.
, Semikolenova N.V.
, Echevskaja L.G.
, Matsko M.A.
Ethylene Polymerization over Homogeneous and Supported Catalysts Based on Bis(imino)pyridine Co(II) Complex: Data on the Number of Active Centers and Propagation Rate Constant
Macromolecular Chemistry and Physics. 2008. V.209. N24. P.2510-2515. DOI: 10.1002/macp.200800376 WOS Scopus РИНЦ ANCAN OpenAlex
Ethylene Polymerization over Homogeneous and Supported Catalysts Based on Bis(imino)pyridine Co(II) Complex: Data on the Number of Active Centers and Propagation Rate Constant
Macromolecular Chemistry and Physics. 2008. V.209. N24. P.2510-2515. DOI: 10.1002/macp.200800376 WOS Scopus РИНЦ ANCAN OpenAlex
Dates:
| Submitted: | Aug 23, 2008 |
| Accepted: | Oct 8, 2008 |
| Published online: | Nov 10, 2008 |
| Published print: | Dec 18, 2008 |
Identifiers:
| Web of science: | WOS:000262275500007 |
| Scopus: | 2-s2.0-58049107551 |
| Elibrary: | 13584570 |
| Chemical Abstracts: | 2009:76594 |
| Chemical Abstracts (print): | 150:306984 |
| OpenAlex: | W1976841894 |