Topics in Catalysis

, Volume 7, Issue 1–4, pp 179–185 | Cite as

Surface science approach to the preparation and characterization of model Ziegler–Natta heterogeneous polymerization catalysts

  • Tamás I. Korányi
  • Enrico Magni
  • Gabor A. SomorjaiEmail author


Ziegler–Natta heterogeneous catalytic systems are extensively used to polymerize ethylene and propylene. Some industrial catalysts consist of TiCl4 chemisorbed on activated MgCl2 and subsequently reduced and alkylated by reaction with an aluminum alkyl (generally AlEt3). Lewis bases are added to the catalytic systems to control the enantio-selectivity for the production of isotactic polypropylene. Our aim is to clarify the chemical composition of the active centers by modern surface science methods. Model catalysts are prepared in the form of ultra-thin films by gas-phase deposition on a gold foil in ultrahigh vacuum. Under these conditions, MgCl2 films grow to controlled thickness via a layer-by-layer mechanism, as revealed by AES and XPS. TiCl4 can be deposited on these films near room temperature by both electron irradiation-induced and metallic magnesium-induced chemical vapor deposition. Angle-resolved XPS studies indicate that these films consist of a few layers of TiCl2 with one monolayer of TiCl4 chemisorbed on its surface. The exposure of these titanium chloride films to the co-catalyst AlEt3 produces an active model Ziegler–Natta catalyst. XPS analysis reveals the presence of TiCl2Et on the catalyst surface: this is believed to be the active site. Prolonged reaction with the co-catalyst reduces the titanium sites to TiClEtn (n = 1 and/or 2). High molecular weight polyethylene and polypropylene are synthesized on these catalysts, as shown by Raman spectroscopy. Highly isotactic polypropylene is produced without need for stereo-regulating Lewis bases.

Ziegler–Natta polymerization model catalyst gas-phase deposition thin film magnesium chloride titanium chloride AES XPS ISS TPD 


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  1. [1]
    J. Boor Jr., Ziegler-Natta Catalysis and Polymerization (Academic Press, New York, 1979).Google Scholar
  2. [2]
    S. van der Ven, Polypropylene and Other Polyolefins: Polymeriza-tion and Characterization (Elsevier, Amsterdam, 1990).Google Scholar
  3. [3]
    E. Albizzati, U. Giannini, G. Collina, L. Noristi and L. Resconi, in: Polypropylene Handbook, ed. E.P. Moore Jr. (Carl Hanser, Munich, 1996) ch. 2.Google Scholar
  4. [4]
    J.J.A. Dusseault and C.C. Hsu, J. Macromol. Sci., Rev. Macromol. Chem. Phys. C 33 (1993) 103.Google Scholar
  5. [5]
    G. Fink, R. M¨ulhaupt and H.H. Brintziger, eds., Ziegler Catalysis (Springer, Heidelberg, 1994).Google Scholar
  6. [6]
    P.C. Barb`e, G. Cecchin and L. Noristi, Adv. Polym. Sci. 81 (1986) 1.CrossRefGoogle Scholar
  7. [7]
    Y.V. Kissin, Isospecific Polymerization of Olefins with Heteroge-neous Ziegler-Natta Catalysts (Springer, New York, 1985).Google Scholar
  8. [8]
    P. Corradini, V. Barone, R. Fusco and G. Guerra, Eur. Polym. J. 15 (1979) 133.CrossRefGoogle Scholar
  9. [9]
    P. Corradini, V. Barone, R. Fusco and G. Guerra, J. Catal. 77 (1982) 32.CrossRefGoogle Scholar
  10. [10]
    P. Corradini, V. Barone and G. Guerra, Macromolecules 15 (1982) 1242.CrossRefGoogle Scholar
  11. [11]
    P. Corradini, V. Barone and G. Guerra, Eur. Polym. J. 20 (1984) 1177.CrossRefGoogle Scholar
  12. [12]
    V. Venditto, G. Guerra, P. Corradini and R. Fusco, Eur. Polym. J. 27 (1991) 45.CrossRefGoogle Scholar
  13. [13]
    P. Corradini and G. Guerra, Prog. Polym. Sci. 16 (1991) 239.CrossRefGoogle Scholar
  14. [14]
    E. Magni and G.A. Somorjai, Appl. Surf. Sci. 89 (1995) 187.CrossRefGoogle Scholar
  15. [15]
    E. Magni and G.A. Somorjai, Surf. Sci. 341 (1995) L1078.CrossRefGoogle Scholar
  16. [16]
    E. Magni and G.A. Somorjai, Surf. Sci. 345 (1996) 1.CrossRefGoogle Scholar
  17. [17]
    E. Magni and G.A. Somorjai, J. Phys. Chem. 100 (1996) 14786.CrossRefGoogle Scholar
  18. [18]
    E. Magni and G.A. Somorjai, J. Phys. Chem., in press.Google Scholar
  19. [19]
    E. Magni and G.A. Somorjai, Surf. Sci. 377 (1997) 824.CrossRefGoogle Scholar
  20. [20]
    E. Magni and G.A. Somorjai, Catal. Lett. 35 (1995) 205.CrossRefGoogle Scholar
  21. [21]
    G.A. Somorjai, Introduction to Surface Chemistry and Catalysis (Wiley, New York, 1994).Google Scholar
  22. [22]
    D.P. Woodruff and T.A. Delchar, Modern Techniques of Surface Science (Cambridge University Press, Cambridge, 1994).Google Scholar
  23. [23]
    D. Briggs and M.P. Seah, Practical Surface Analysis, Vol. 1 (Wiley, Baffins Lane, Chichester, 1990).Google Scholar
  24. [24]
    J.L. K¨onig, Spectroscopy of Polymers (American Chemical Society, Washington, DC, 1992) (Series title: ACS professional reference book).Google Scholar
  25. [25]
    D.L. Bower and W.F. Maddams, The Vibrational Spectroscopy of Polymers (Cambridge University Press, New York, 1988).Google Scholar
  26. [26]
    D.O. Hummel, in: Polymer Spectroscopy, ed. D.O. Hummel (Chemie, Weinheim, 1974).Google Scholar
  27. [27]
    E. Schr¨oder, G. M¨uller and K.-F. Arndt, Polymer Characterization (Carl Hanser, M¨unchen, 1989).Google Scholar
  28. [28]
    P.J. Hendra and J.K. Agbenyega, The Raman Spectra of Polymers (Wiley, New York, 1993).Google Scholar
  29. [29]
    J.L. K¨onig, Spectrochim. Acta 22 (1966) 1223.CrossRefGoogle Scholar
  30. [30]
    J.L. K¨onig, L.E. Wolfram and J.G. Grasselli, Spectrochim. Acta 22 (1966) 1233.CrossRefGoogle Scholar
  31. [31]
    C.D. Bain, J. Chem. Soc. Faraday Trans. 91 (1995) 1281.CrossRefGoogle Scholar
  32. [32]
    Y.R. Shen, Nature 337 (1989) 519.CrossRefGoogle Scholar
  33. [33]
    Y.R. Shen, Ann. Rev. Phys. Chem. 40 (1989) 327.CrossRefGoogle Scholar
  34. [34]
    P. Guyot-Sionnest and Y.R. Shen, Phys. Rev. B 35 (1987) 4420.CrossRefGoogle Scholar
  35. [35]
    P. Guyot-Sionnest, J.H. Hunt and Y.R. Shen, Phys. Rev. Lett. 59 (1987) 1597.CrossRefGoogle Scholar
  36. [36]
    D. Zhang, Y.R. Shen and G.A. Somorjai, Chem. Phys. Lett. 281 (1997) 394.CrossRefGoogle Scholar
  37. [37]
    D.H. Fairbrother, J.G. Roberts, S. Rizzi and G.A. Somorjai, Lang-muir 13 (1997) 2090.CrossRefGoogle Scholar
  38. [38]
    D.H. Fairbrother, J.G. Roberts and G.A. Somorjai, Surf. Sci. 399 (1998) 109.CrossRefGoogle Scholar
  39. [39]
    J.G. Roberts, M. Gierer, D.H. Fairbrother, M.A. Van Hove and G.A. Somorjai, Surf. Sci. 399 (1998) 123.CrossRefGoogle Scholar

Copyright information

© Kluwer Academic Publishers 1999

Authors and Affiliations

  • Tamás I. Korányi
    • 1
  • Enrico Magni
    • 2
  • Gabor A. Somorjai
    • 1
    • 2
    Email author
  1. 1.Materials Sciences DivisionLawrence Berkeley National Laboratory, University of CaliforniaBerkeleyUSA
  2. 2.Department of ChemistryUniversity of CaliforniaBerkeleyUSA

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