JZUS - Journal of Zhejiang University SCIENCE

Journal of Zhejiang University SCIENCE A 2004 Vol.5 No.8 P.912-917

http://doi.org/10.1631/jzus.2004.0912

Study on the distribution of active centers in novel low Ti-loading MgCl₂-supported Ziegler-Natta catalyst

Author(s): WANG Jian-feng, WANG Li, ZHAO Zhen-rong, WANG Wen-qing, CHEN Tao
Affiliation(s): State Key Lab of Polymer Reaction Engineering, College of Materials Science and Chemical Engineering, Zhejiang University, Hangzhou 310027, China; more
Corresponding email(s): opl_wl@dial.zju.edu.cn
Key Words: Supported Ziegler-Natta catalyst, Propylene polymerization, Active center, Molecular weight distribution

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Abstract: Novel MgCl₂-supported Ziegler-Natta (Z-N) catalysts prepared using a new one-pot ball milling method can effectively control the amounts of Ti-loading in the catalysts. Complex GPC data on polypropylene synthesized by these novel catalysts were analyzed using the method of fitting the molecular weight distribution (MWD) curves with a multiple Flory-Schulz function. It was found that multiple active centers exist in these novel catalysts. Detailed study of the effects of the Ti-loadings in the catalysts on the distribution of the active centers showed that the Ti-loadings in the novel MgCl₂-supported Z-N catalysts might affect the proportion of each type of active centers; and might be the main factor responsible for the effect of the Ti-loadings on the microstructure, the molecular weight and molecular weight distribution width of the resultant polymer, the catalytic activity and polymerization kinetics.

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