Polymerization of ethylene using supported zirconocene catalysts

The polymerization of ethylene using supported zirconocene catalysts with varying support compositions SiO2-MAO-Me2Si(Ind)(2)ZrCl2 + TIBA (catalyst I) and MgCl2-Me2Si(Ind)(2)ZrCl2 + TIBA (catalyst II) (MAO is methylaluminoxane, Ind is indenyl, and TIBA is triisobutylaluminum) was studied. The examined catalytic systems differ in their activity, ability to control the molecular mass of the resulting polymer, and kinetics of copolymerization with l-hexene. The molecular structure of PE prepared with supported catalysts I and II and a homogeneous catalyst Me2Si(Ind)(2)ZrCl2 + MAO was studied by IR and C-13 NMR spectroscopy. As evidenced by C-13 NMR spectroscopy, PE samples synthesized with the homogeneous catalyst and catalyst I contain ethyl branches along with the end methyl groups in the low-molecular-mass fractions. On the contrary, PE prepared with supported catalyst II is devoid of ethyl branches but contains vinyl groups as the basic type of unsaturation.