期刊
JOURNAL OF CATALYSIS
卷 369, 期 -, 页码 276-282出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jcat.2018.11.008
关键词
Ethylene/1-hexene copolymerization; Number of active centers; Polymerization kinetics; Propagation rate constant; Ziegler-Natta catalysts
资金
- Ministry of Education and Science of the Russian Federation
We present data on the number of active centers (C-p) and the propagation rate constant (k(p)) upon copolymerization of ethylene and 1-hexene over supported titanium-magnesium catalysts of different compositions obtained by polymerization quenching with radioactive carbon monoxide ((CO)-C-14). The rise in ethylene/1-hexene copolymerization rate as compared to the rate of homopolymerization (the comonomer effect) is found to be related to the increase in the calculated propagation rate constant. Meanwhile, the increased 1-hexene concentration results in a higher calculated k(p) value. Addition of 1-hexene during ethylene polymerization also increases the polymerization rate by raising the calculated k(p) value. These findings demonstrate that the comonomer effect is caused by the increase in monomer concentration in the copolymer layer that is formed on a catalyst particle and is characterized by reduced crystallinity as compared to that of homopolymer. The decline in the copolymerization rate with time is caused by reduction of the number of active centers. (C) 2018 Elsevier Inc. All rights reserved.
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