Skip to main content

Preparation of LLDPE through tandem ethylene polymerization using chromium and zirconium catalysts


The effective tandem catalysis systems including the trimerization catalyst of CrCl3/SNS [SNS = bis-(2-pentylsulfanyl-ethyl)-amine] and the copolymerization catalyst of rac-ethylene bis(indenyl) zirconium (IV) dichloride have been introduced. The CrCl3/SNS catalyst was synthesized via reaction between CrCl3(THF)3 precursor and SNS as efficient ligand at room temperature. An ethylene trimerization reaction at 90 °C and 23 bar ethylene, using the CrCl3/SNS complex activated by 700 equivalents of methylaluminoxane, afforded 99.9 % 1-C6. Only 0.10 % PE was produced. Effect of different parameters such as ethylene pressure and Cr/Zr ratio was investigated during tandem polymerization. Successive increases in the CrCl3/SNS amount yielded a series of copolymer samples with decreased T m and X c. The butyl branches of produced polymer were identified by 13C NMR analysis. Data from dynamic mechanical thermal analysis indicated formation of various polymeric materials with the branches, which their stiffness varied according to the Cr/Zr ratio used in the polymerization reaction.

This is a preview of subscription content, access via your institution.

Scheme 1
Scheme 2
Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6
Fig. 7
Fig. 8
Fig. 9


  1. Zohuri G, Jamjah R, Ahmadjo S (2005) Polymerization of ethylene using Cp2ZrCl2 metallocene and methylaluminoxane homogeneous catalyst system. Iran Polym J 14:111–116

    CAS  Google Scholar 

  2. Peacock AJ (2000) Handbook of polyethylene: structures, properties, and applications. Marcel Dekker, New York

    Google Scholar 

  3. Mcknight AL, Waymouth RM (1998) Group 4 ansa-cyclopentadienyl-amido catalysts for olefin polymerization. Chem Rev 98:2587–2598

    Article  CAS  Google Scholar 

  4. Wasilke JC, Obrey SJ, Baker RT, Bazan GC (2005) Concurrent tandem catalysis. Chem Rev 105:1001–1020

    Article  CAS  Google Scholar 

  5. Komon ZJA, Bazan GC (2001) Synthesis of branched polyethylene by tandem catalysis. Macromol Rapid Commun 22:467–478

    Article  CAS  Google Scholar 

  6. Ye Z, Al Obaidi F, Zhu S, Subramanian R (2005) Long-chain branching and rheological properties of ethylene–1-hexene copolymers synthesized from ethylene stock by concurrent tandem catalysis. Macomol Chem Phys 206:2096–2105

    Article  CAS  Google Scholar 

  7. Jiang T, Huang Z, Luo M, Chen H, Ning Y (2008) Preparation of ethylene/1-octene copolymers from ethylene stock with tandem catalytic system. J Appl Polym Sci 107:3071–3075

    Article  CAS  Google Scholar 

  8. Zhang Z, Cui N, Lu Y, Ke Y, Hu Y (2005) Preparation of linear low-density polyethylene by the in situ copolymerization of ethylene with an iron oligomerization catalyst and rac-ethylene bis(indenyl) zirconium (IV) dichloride. J Polym Sci Part A Polym Chem 43:984–993

    Article  CAS  Google Scholar 

  9. Bianchini C, Giambastiani G, Meli A, Guerrero Rios I, Toti A, Passaglia E, Frediani M (2008) LLDPE with exclusively ethyl branches by tandem catalysis with single-site Zr(IV)/Co(II) catalysts. Top Catal 48:107–113

    Article  CAS  Google Scholar 

  10. Al Obaidi F, Ye Z, Zhu S (2004) Direct synthesis of linear low-density polyethylene of ethylene/1-hexene from ethylene with a tandem catalytic system in a single reactor. J Polym Sci Part A Polym Chem 42:4327–4336

    Article  CAS  Google Scholar 

  11. Ye Z, AlObaidi F, Zhu S (2004) A tandem catalytic system for synthesis of ethylene–1-hexene copolymers from ethylene stock. Macromol Rapid Commun 25:647–652

    Article  CAS  Google Scholar 

  12. Bianchini C, Frediani M, Giambastiani G, Kaminsky W, Meli A, Passaglia E (2005) Amorphous polyethylene by tandem action of cobalt and titanium single-site catalysts. Macromol Rapid Commun 26:1218–1223

    Article  CAS  Google Scholar 

  13. Mohamadnia Z, Ahmadi E, Nekoomanesh Haghighi M, Salehi-Mobarakeh H (2011) Synthesis and optimization of ethylene trimerization using [bis-(2-dodecylsulfanyl-ethyl)-amine]CrCl3 catalyst. Catal Lett 141:474–480

    Article  CAS  Google Scholar 

  14. Galland GB, de Souza RF, Mauler RS, Nunes FF (1999) 13CNMR determination of the composition of linear low-density polyethylene obtained with [η 3-methallyl-nickel-diimine]PF6 complex. Macromolecules 32:1620–1625

    Article  CAS  Google Scholar 

  15. Ahmadi E, Mohamadnia Z, Nekoomanesh Haghighi M (2011) High productive ethylene trimerization catalyst based on CrCl3/SNS ligands. Catal Lett 141:1191–1198

    Article  CAS  Google Scholar 

  16. Zhu BC, Guo CY, Liu ZY, Yin YQ (2004) In situ copolymerization of ethylene to produce linear-low-density polyethylene by Ti(OBu)4/AlEt3-MAO/SiO2/Et(Ind)2ZrCl2. J Appl Polym Sci 94:2451–2455

    Article  CAS  Google Scholar 

  17. Koivumaki J, Seppala JV (1993) Observations on the rate enhancement effect with magnesium chloride/titanium tetrachloride and dicyclopentadienylzirconium dichloride (Cp2ZrCl2) catalyst systems upon 1-hexene addition. Macromolecules 26:5535–5538

    Article  CAS  Google Scholar 

  18. Zhang J, Li BG, Fan H, Zhu S (2007) Synthesis of ethylene–1-hexene copolymers from ethylene stock by tandem action of bis(2-dodecylsulfanyl-ethyl) amine-CrCl3 and Et(Ind)2ZrCl2. J Polym Sci Part A Polym Chem 45:3562–3569

    Article  CAS  Google Scholar 

  19. Xu G, Ruckenstein E (1998) Ethylene copolymerization with 1-octene using a 2-methylbenz[e]indenyl-based ansa-monocyclopentadienylamido complex and methylaluminoxanes catalyst. Macromolecules 31:4724–4729

    Article  CAS  Google Scholar 

  20. Rana SK (2000) Transformation of morphology of as-extrudates of high-density linear low-density polyethylene drawn. Iran Polym J 9:229–238

    CAS  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding authors

Correspondence to Zahra Mohamadnia or Ebrahim Ahmadi.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Mohamadnia, Z., Ahmadi, E., Haghighi, M.N. et al. Preparation of LLDPE through tandem ethylene polymerization using chromium and zirconium catalysts. Iran Polym J 24, 621–628 (2015).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


  • Ethylene
  • Trimerization
  • Polymerization
  • 1-Hexene
  • Tandem