Shandong Provincial Key Laboratory of Olefin Catalysis and Polymerization, Key Laboratory of Rubber-Plastics (Ministry of Education), School of Polymer Science and Engineering, Qingdao University of Science and Technology, Qingdao 266042, China
ahhe@qust.edu.cn; aihuahe@iccas.ac.cn
收稿:2020-04-07,
修回:2020-6-13,
录用:2020-6-23,
网络首发:2020-08-24,
纸质出版:2021-01-01
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Zheng, W. P.; Ma, Y. P.; Du, D. L.; He, A. H.; Shao, H. F.; Liu, C. G. Polymerization kinetics of propylene with the MgCl2-supported Ziegler-Natta catalysts—active centers with different tacticity and fragmentation of the catalyst. Chinese J. Polym. Sci. 2021, 39, 70–80 DOI: 10.1007/s10118-020-2473-z.
Wei-Ping Zheng, Ya-Ping Ma, Da-Lin Du, et al. Polymerization Kinetics of Propylene with the MgCl2-Supported Ziegler-Natta Catalysts—Active Centers with Different Tacticity and Fragmentation of the Catalyst[J]. Chinese Journal of Polymer Science, 2021, 39(1): 70-80. DOI: 10.1007/s10118-020-2473-z.
Zheng, W. P.; Ma, Y. P.; Du, D. L.; He, A. H.; Shao, H. F.; Liu, C. G. Polymerization kinetics of propylene with the MgCl2-supported Ziegler-Natta catalysts—active centers with different tacticity and fragmentation of the catalyst. Chinese J. Polym. Sci. 2021, 39, 70–80 DOI: 10.1007/s10118-020-2473-z. DOI:
Wei-Ping Zheng, Ya-Ping Ma, Da-Lin Du, et al. Polymerization Kinetics of Propylene with the MgCl2-Supported Ziegler-Natta Catalysts—Active Centers with Different Tacticity and Fragmentation of the Catalyst[J]. Chinese Journal of Polymer Science, 2021, 39(1): 70-80. DOI: 10.1007/s10118-020-2473-z. DOI:
The catalytic activity and stereospecificity of olefin polymerization by using heterogeneous TiCl
4
/MgCl
2
Ziegler-Natta (Z-N) catalysts are determined by the structure and nature of active centers
which are mysterious and fairly controversial. In this work
the propylene polymerization kinetics under different polymerization temperatures by using Z-N catalysts were investigated through monitoring the concentration of active centers [C*] with different tacticity. SEM was applied to characterize the catalyst morphologies and growing polypropylene (PP) particles. The lamellar thickness and crystallizability of PP obtained under different polymerization conditions were analyzed by DSC and SAXS. The PP fractions and active centers with different tacticity were obtained with solvent extraction fractionation method. The catalytic activity
active centers with different tacticity and propagation rate constant
k
p
fragmentation of the catalyst
crystalline structure of PP are correlated with temperature and time for propylene polymerizations. The polymerization temperature and time show complex influences on the propylene polymerization. The higher polymerization temperature (60 °C) resulted higher activity
k
p
and lower [C*]
and the isotactic active centers C
i
* as the majority ones producing the highest isotactic polypropylene (
i
PP) components showed much higher
k
p
when compared with the active centers with lower stereoselectivity. Appropriate polymerization time provided full fragmentation of the catalyst and minimum diffusion limitation. This work aims to elucidate the formation and evolution of active centers with different tacticity under different polymerization temperature and time and its relations with the fragmentation of the PP/catalyst particles
and provide the solutions to the improvement of catalyst activity and isotacticity of PP.
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