Support Influence of Metallocene Catalysts on Ethylene Polymerization Activity

Abstract

Metallocenes give the possibility to tailor the structure of polymers in a way that has not been reached before by either Phillips or Ziegler-Natta catalysts. Heterogeneous metallocene catalysts are activated by methylaluminoxane (MAO) and generally supported on porous materials. Multiple parameters in the synthesis of the support were varied, which resulted in a trend in polymerization activity. Reasons for this trend in polymerization activity could be the difference in number of acid sites, the difference in acidity per site or the easier fragmentation of the various supports. By using infrared (IR) spectroscopy with pyridine as probe molecule, the Lewis acidity of the samples was determined. Diffuse Reflectance IR Fourier Transform Spectroscopy (DRIFTS) was used to study the fragmentation time of the samples. Subsequently, the catalyst particles were stained with a perylene derivative to obtain fluorescence, which enabled the use of Confocal Fluorescence Microscopy (CFM) to visualize the fragmentation. The combination of these techniques gave insight into the influence of the support on the polymerization activity of metallocene catalysts.