Late transition metal catalyst for olefin polymerization and preparation method thereof

Abstract

The invention provides a late transition metal catalyst for olefin polymerization with a structural formula (I), which is characterized by introducing a wedge-shaped dendritic molecule having certain space volume and more symmetrical spatial position of substituent into a ligand structure, successfully avoiding chain transfer reaction of propylene and effectively preventing the propylene from attacking the active site from the side chain. When the catalyst for the olefin polymerization is used for propylene polymerization together with an aluminium alkyl compound, the polymerization activity is remarkably improved, the activity of the catalyst can reach 105g polypropylene/mol Fe*h, and in particular, the number-average molecular weight and degree of isotacticity of the polymerization product are enhanced. The number-average molecular weight is far more than 15000g/mol, and the degree of isotacticity is close to 85%. M is a transition metal selected from Fe, Co or Ni.

Description

technical field The invention relates to an olefin polymerization catalyst and a preparation method thereof, in particular to a late transition metal propylene polymerization catalyst containing pyridinediimine wedge-shaped dendritic ligands and a preparation method thereof. Background technique In recent years, late transition metal catalysts represented by nickel, iron and cobalt series have shown quite high activity in ethylene polymerization, and thus become one of the important members in the field of polyolefin catalysts. There are many literature reports on late transition metal catalysts and their homo(co)polymerization of ethylene. Such as literature 1 (Adnan S, Abu-Surrah, Kristian Lappalainen, Ulla Piironen, et al. "Newbis (imino) pyridine-iron (II) and cobalt (II)-based catalysts: synthesis, characterization and activity towards polymerization of ethylene", Journal of Organometallic Chemistry, 648(2002): 55-61.), Document 2 (Ivanchev S.S., Tolstikov G.A., Badaev...

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Problems solved by technology

However, the existing post-transition metal catalysts are still unsatisfactory for the polymerization of propylene, and the number-average molecular weight of the prepared polypropylene is relatively low (the number-average molecular weight is not more than 15000), and the isotacticity is lower than 70% (Small B.L., BrookhartM. "Polymerization of Propylene by a New Generation of Iron Catalysts: Mechanisms of ChainInitiation, Propagation, and Termination", Macromolecules, 1999, 32: 2120-2130; Zhu Yong, Xu Wei, Luo Zhenghong. Application of Catalysts in Propylene Polymerization", Industrial Catalysis, 2008, 16: 45-49.)

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