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Alkylaluminium/Borate systems for activation of metallocene catalysts in ethylene polymerization: ligand effects and reaction parameter optimization.

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Title: Alkylaluminium/Borate systems for activation of metallocene catalysts in ethylene polymerization: ligand effects and reaction parameter optimization.
Authors: Choudhary, Narendra Singh1 (AUTHOR), Mallick, Soumita Basu1 (AUTHOR), Ghar, Priyanka1 (AUTHOR), Pradhan, Narayan C.1 (AUTHOR) ncp@che.iitkgp.ac.in
Source: Journal of Polymer Research. Dec2025, Vol. 32 Issue 12, p1-10. 10p.
Subjects: Metallocene catalysts, Polymerization, Polyethylene, Molecular weights, Ligands (Chemistry), Catalysts, Borates, Alkyl compounds
Abstract: Activation of metallocene catalysts using organoborate compounds in conjunction with alkylaluminium has demonstrated the production of polyolefins with tailored properties over modified methylaluminoxane (MMAO). This study examines the impact of reaction parameters on ethylene polymerization utilizing borate-activated metallocene catalysts in order to identify optimal conditions for catalyst activity and polymer characteristics. It further investigates the synergistic influence of catalyst ligand structures and different alkylaluminium compounds on catalyst activity, molecular weight (MW), and molecular weight distribution (MWD), providing insights into their effects on polymerization pathways. This study employed metallocene catalysts such as Bis(cyclopentadienyl)zirconium dichloride (Zr1), rac-Ethylenebis(indenyl)zirconium dichloride (Zr2), Bis(butylcyclopentadienyl)zirconium dichloride (Zr3) and Bis(cyclopentadienyl)hafnium dichloride (Hf1), activated with either MMAO or Organoborate, alongside cocatalysts triethylaluminium (TEA) and triisobutylaluminium (TIBA) for ethylene polymerization. Catalyst activity, particularly for Zr2, was observed to peak at 80 °C. Additionally, an increase in temperature led to a decrease in polymer MW attributed to accelerated chain transfer reactions, resulting in broader MWD. Catalyst activity was highest in the initial stages of the reaction and diminished as the reaction progressed. Increasing catalyst concentrations from 0.02 × 10–3 to 0.08 × 10–3 mol. L−1 negatively impacted both activity and MW. Similarly, increased borate concentration showed minimal effect on activity and MW. Furthermore, elevating the [Al]/[Zr] ratio increased activity but resulted in shorter polymer chains due to faster chain transfer reactions. The combination of borate with different alkylaluminium cocatalysts exhibited a selective advantage in MW, with the order of preference being TIBA > TIBA + TEA > TEA, as bulkier alkylaluminium limits chain transfer due to steric hindrance. [ABSTRACT FROM AUTHOR]
Copyright of Journal of Polymer Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Alkylaluminium/Borate systems for activation of metallocene catalysts in ethylene polymerization: ligand effects and reaction parameter optimization.
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  Data: <searchLink fieldCode="JN" term="%22Journal+of+Polymer+Research%22">Journal of Polymer Research</searchLink>. Dec2025, Vol. 32 Issue 12, p1-10. 10p.
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  Data: Activation of metallocene catalysts using organoborate compounds in conjunction with alkylaluminium has demonstrated the production of polyolefins with tailored properties over modified methylaluminoxane (MMAO). This study examines the impact of reaction parameters on ethylene polymerization utilizing borate-activated metallocene catalysts in order to identify optimal conditions for catalyst activity and polymer characteristics. It further investigates the synergistic influence of catalyst ligand structures and different alkylaluminium compounds on catalyst activity, molecular weight (MW), and molecular weight distribution (MWD), providing insights into their effects on polymerization pathways. This study employed metallocene catalysts such as Bis(cyclopentadienyl)zirconium dichloride (Zr1), rac-Ethylenebis(indenyl)zirconium dichloride (Zr2), Bis(butylcyclopentadienyl)zirconium dichloride (Zr3) and Bis(cyclopentadienyl)hafnium dichloride (Hf1), activated with either MMAO or Organoborate, alongside cocatalysts triethylaluminium (TEA) and triisobutylaluminium (TIBA) for ethylene polymerization. Catalyst activity, particularly for Zr2, was observed to peak at 80 °C. Additionally, an increase in temperature led to a decrease in polymer MW attributed to accelerated chain transfer reactions, resulting in broader MWD. Catalyst activity was highest in the initial stages of the reaction and diminished as the reaction progressed. Increasing catalyst concentrations from 0.02 × 10–3 to 0.08 × 10–3 mol. L−1 negatively impacted both activity and MW. Similarly, increased borate concentration showed minimal effect on activity and MW. Furthermore, elevating the [Al]/[Zr] ratio increased activity but resulted in shorter polymer chains due to faster chain transfer reactions. The combination of borate with different alkylaluminium cocatalysts exhibited a selective advantage in MW, with the order of preference being TIBA > TIBA + TEA > TEA, as bulkier alkylaluminium limits chain transfer due to steric hindrance. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Polymer Research is the property of Springer Nature and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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RecordInfo BibRecord:
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      – Type: doi
        Value: 10.1007/s10965-025-04673-w
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 10
        StartPage: 1
    Subjects:
      – SubjectFull: Metallocene catalysts
        Type: general
      – SubjectFull: Polymerization
        Type: general
      – SubjectFull: Polyethylene
        Type: general
      – SubjectFull: Molecular weights
        Type: general
      – SubjectFull: Ligands (Chemistry)
        Type: general
      – SubjectFull: Catalysts
        Type: general
      – SubjectFull: Borates
        Type: general
      – SubjectFull: Alkyl compounds
        Type: general
    Titles:
      – TitleFull: Alkylaluminium/Borate systems for activation of metallocene catalysts in ethylene polymerization: ligand effects and reaction parameter optimization.
        Type: main
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            NameFull: Choudhary, Narendra Singh
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            NameFull: Mallick, Soumita Basu
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            NameFull: Ghar, Priyanka
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            NameFull: Pradhan, Narayan C.
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          Dates:
            – D: 01
              M: 12
              Text: Dec2025
              Type: published
              Y: 2025
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              Value: 32
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              Value: 12
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            – TitleFull: Journal of Polymer Research
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