Probing the Coordinative Unsaturation and Local Environment of Ti3+ Sites in an Activated High‐Yield Ziegler–Natta Catalyst |
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| Authors: | Elena Morra Prof Elio Giamello Prof Sabine Van Doorslaer Giuseppe Antinucci Dr Maddalena D'Amore Prof Vincenzo Busico Prof Mario Chiesa |
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| Affiliation: | 1. Dipartimento di Chimica and NIS, Università degli Studi di Torino, Via Giuria 7, 10125 Torino (Italy);2. Dutch Polymer Institute(DPI), P.O. Box 902, 5600 AX Eindhoven (The Netherlands);3. Department of Physics, University of Antwerp, Universiteitsplein 1, B‐2610 Antwerp‐Wilrijk (Belgium);4. Dipartimento di Scienze Chimiche, Università degli Studi di Napoli Federico II, Via Cintia 21, 80126 Napoli (Italy) |
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| Abstract: | The typical activation of a fourth generation Ziegler–Natta catalyst TiCl4/MgCl2/phthalate with triethyl aluminum generates Ti3+ centers that are investigated by multi‐frequency continuous wave and pulse EPR methods. Two families of isolated, molecule‐like Ti3+ species have been identified. A comparison of the experimentally derived g tensors and 35,37Cl hyperfine and nuclear‐quadrupole tensors with DFT‐computed values suggests that the dominant EPR‐active Ti3+ species is located on MgCl2(110) surfaces (or equivalent MgCl2 terminations with tetra‐coordinated Mg). O2 reactivity tests show that a fraction of these Ti sites is chemically accessible, an important result in view of the search for the true catalyst active site in olefin polymerization. |
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| Keywords: | EPR spectroscopy heterogeneous catalysis polymerization titanium Ziegler– Natta catalysts |
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