Car—Parrinello study of Ziegler—Natta heterogeneous catalysis: stability and destabilization problems of the active site models |
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| Authors: | MAURO BOERO MICHELE PARRINELLO KIYOYUKI TERAKURA HORST WEISS |
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| Institution: | 1. Joint Research Center for Atom Technology , Angstrom Technology Partnership (JRCAT-ATP) , 1-1-1 Higashi, Tsukuba, Ibaraki, 305-0046, Japan;2. Swiss Center for Scientific Computing (CSCS)/ETH Zurich , via Cantonale, Galeria 2, CH-6928, Manno, Switzerland;3. Physical Chemistry Department , ETH H?nggerberg, Baustelle HCI , CH-8093, Zurich, Switzerland;4. Joint Research Center for Atom Technology , National Agency of Industrial Science and Technology (AIST) , 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8562, Japan;5. BASF AG, Polymer Research Division , D-67056, Ludwigshafen, Germany |
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| Abstract: | Recent results on Car—Parrinello simulations of MgCl2/TiCl4 Ziegler—Natta heterogeneous catalytic systems are reviewed and the stability of Ti active site configurations on the various active surfaces are discussed. In particular, the focus is on the ability of an active centre to carry out the polymerization process efficiently, achieved by monitoring geometrical changes and associated energetics during the reaction. The active site geometry is crucial in enhancing or decreasing the activation barrier, in selecting the olefin enantioface and in some cases in destabilizing the catalytic centre. A key point in the binding/destabilization interplay is the matching of Ti with the substrate, an issue that represents a fundamental difference with respect to homogeneous systems. |
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