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  • 1 Instituto Politécnico de Santarém-ESAS Apartado 310 2004 Santarém Codex Portugal
  • | 2 C.Q.E.-I.S.T. Av. Rovisco Pais 1096 Lisboa Codex Portugal
  • | 3 UMIST Department of Chemistry M60 1QD Manchester UK
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The subject of this work is ethylene polymerisation using Kaminsky type catalysts: Cp2MR2=methylaluminoxane [M=Zr, W, Nb; R=Cl, CH3]. Active center determination and kinetic studies of the (Cp2WCl2+methylaluminoxane) and Cp2ZrCl2+methylaluminoxane) systems are described, using a quenching method with tritiated methanol. The activity of the polymer was determined by liquid scintillation counting. We have found 0.5% and 87% of active centers, respectively for W and Zr system. The catalytic activity of complexes Cp2WCl2 and Cp2NbCl2 was compared with that of Cp2ZrCl2. The W and Nb complexes are found to be less active than the Zr complex.