Kinetics of Ethylene Polymerization in the Presence of a Homogeneous Catalyst Based on a bis(Phenoxyimine) Complex of Zirconium(IV)
Full article
| Общее |
Language:
Английский,
Genre:
Full article,
Status:
Published,
Source type:
Translated
|
| Journal |
Kinetics and Catalysis
ISSN: 0023-1584
, E-ISSN: 1608-3210
|
| Output data |
Year: 2011,
Volume: 52,
Number: 2,
Pages: 217-221
Pages count
: 5
DOI:
10.1134/S0023158411020017
|
| Authors |
Barabanov A.A.
1
,
Semikolenova N.V.
1
,
Matsko M.A.
1
,
Echevskaya L.G.
1
,
Zakharov V.A.
1
|
| Affiliations |
| 1 |
Boreskov Institute of Catalysis SB RAS
|
|
Funding (1)
|
1
|
Russian Foundation for Basic Research
|
07-03-00311
|
Changes in the molecular-weight characteristics of the product of ethylene polymerization in the course of reaction in the presence of a homogeneous catalytic system and in the number and reactivity of catalyst active sites were studied. The catalytic system consisted of bis[N-(3-tert-butylsalicylidene)anilinato]zirconium dichloride and methylalumoxane as an activator. This catalytic system exhibited the signs of unsteady-state conditions: the rate of polymerization dramatically decreased as the reaction time increased. At the onset of polymerization (to 5 min), the catalyst was single-site, and it produced low-molecular-weight polyethylene with M w = (4–10) × 103 g/mol. The fraction of active sites at the initial point in time was as high as 11% based on the initial amount of the zirconium complex. The reactivity of these centers was very high (the rate constant of polymer chain growth was 5.4 × 104 l mol−1 s−1 at 35°C). As the polymerization time increased, the number of active sites decreased and the molecular-weight distribution of polyethylene broadened because of the decay of a portion of initial centers and the formation of new centers that produced high-molecular-weight polyethylene with M w to 130 × 104 g/mol. The propagation rate constant measured at a sufficiently long polymerization time (20 min) was lower than that at the initial point in time; this fact suggests the much lower reactivity of the new active sites.