Supported modified zirconocene catalyst for ethylene polymerization

Abstract

The reactivity of the silyl ether-substituted zirconocene [Zr{η 5-C 5H 4(CH 2) 3OSiMe 3}(η 5-C 5H 5)Cl 2] ( 1) towards dehydroxylated silica was evaluated and comparative studies with respect to the unmodified analogue [Zr(η 5-C 5H 5) 2Cl 2] ( 2) were performed. The different reactions were monitored by FT-IR spectroscopy. The resulting materials were activated with MAO and the catalytic systems were evaluated in ethylene polymerization. The catalysts were characterized by elemental analysis as well as by FT-IR and UV–vis spectroscopy. In addition to the classical reaction between Zr Cl bonds and acidic silanol surface groups, grafting of complex 1 occurs to some extent by reaction between the silyl ether group and reactive siloxane bridges on the silica surface. In contrast, complex 2, as one would expect, only reacts through the Zr Cl groups. Supporting zirconocene 1 on MAO-modified silica gives rise to a more efficient catalyst. The effects caused by these different grafting reactions, as well as the catalytic activities of the resulting materials, are presented and discussed.