Cyclopentadienyl Surface as a Support for Zirconium Polyethylene Catalysts

A novel ethylene polymerization catalyst is prepared by supporting CpZrCl 3 on chemically modified silica. The surface modification of silica was carried out by utilizing the saturated gas−solid reactions of a silane coupling agent, Cp(CH 2 ) 3 Si(OCH 2 CH 3 ) 3, and a partially dehydroxylated silica. Immobilization of CpZrCl 3 onto the cyclopentadienyl surface formed on the silica was done using liquid-phase reactions. The stepwise-prepared materials were characterized by 13 C and 29 Si solid state NMR and FT-IR spectroscopy. This supported catalyst system has a high activity and can be used to produce polyethylene with a narrow molecular weight distribution in the presence of methylaluminoxane. The immobilization of CpZrCl 3 on the cyclopentadienyl surface of SiO 2 more than doubled the polymerization activity of CpZrCl 3 . However, the direct heterogenization of CpZrCl 3 onto an unmodified, partially dehydroxylated silica produced a catalyst with a very low activity. The effect of surface modification reactions and structure of the support on the catalyst performance is presented and discussed.