Immobilization of metallocene within silica-titania by a non-hydrolytic sol-gel method

Bis(cyclopentadienyl)zirconium dichloride was immobilized within binary oxides of SiO2-TiO2 via a non-hydrolytic sol-gel route. Different coordinatively unsaturated Ti species were identified within the oxide structure depending on the TiO2 content, which can interact with the encapsulated metallocene complex and affect its catalystic performance in ethylene polymerization. The catalysts were shown to be active in the polymerization using MAO as the cocatalyst in a low Al/Zr ratio. High molecular weight polymer was obtained, probably due to the suppression of chain termination reactions that occur by beta-elimination. Furthermore, oxide network structures are suggested from analysis of the catalysts (via Rutherford backscattering spectrometry, infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, diffuse pulse voltammetry), molecular simulation and polymerization performance. (C) 2008 Elsevier B.V. All rights reserved.