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Chinese Journal of Polymer Science

, Volume 37, Issue 10, pp 1023–1030 | Cite as

Deactivation Effect Caused by Catalyst-Cocatalyst Pre-contact in Propylene Polymerization with MgCl2-supported Ziegler-Natta Catalyst

  • Zhen Zhang
  • Bai-Yu Jiang
  • Biao Zhang
  • Zhi-Sheng Fu
  • Zhi-Qiang FanEmail author
Article
  • 12 Downloads

Abstract

Propylene slurry polymerization with a MgCl2-supported Ziegler-Natta catalyst containing internal electron donor was conducted after different durations of pre-contact of the catalyst with triethylaluminum cocatalyst. The number of active centers ([C*]/[Ti]) was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and measuring sulfur content in the polymer. The pre-contact treatment caused selective deactivation of a part of active centers with low stereoselectivity and much lower activity in the initial stage of polymerization as compared with the polymerization run without the pre-contact stage. The active center concentration and polymerization activity decreased with prolonging of the pre-contact stage. The proportion of stereoselective active centers was increased by prolonging the pre-contact stage, so the isotacticity of produced polypropylene was enhanced. Release of active centers through catalyst particle fragmentation was significantly retarded, and the polymerization rate curve changed from decay type to induction type by the precontact treatment. In the induction period both non-stereoselective and stereoselective active centers were released and activated, resulting in gradual reduction of the polymer’s isotacticity in the first 5–10 min of polymerization. Selective deactivation of non-stereoselective active centers also took place in propylene polymerization using the catalyst without pre-contacting with the cocatalyst. In this case, the polymerization rate decayed with time after a short induction period of 2–5 min. Over reduction of the active center precursors with low stereoselectivity by triethylaluminum was considered as the reason for their deactivation during the pre-contact or the polymerization processes.

Keywords

Propylene Polymerization Supported Ziegler-Natta catalyst Cocatalyst Pre-contact 

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Notes

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (No. 51773178).

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Copyright information

© Chinese Chemical Society Institute of Chemistry, Chinese Academy of Sciences Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Zhen Zhang
    • 1
  • Bai-Yu Jiang
    • 1
  • Biao Zhang
    • 1
  • Zhi-Sheng Fu
    • 1
  • Zhi-Qiang Fan
    • 1
    Email author
  1. 1.Ministry of Education Key Laboratory of Macromolecular Synthesis and Functionalization, Department of Polymer Science and EngineeringZhejiang UniversityHangzhouChina

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