Characterization of Supported Metallocene Catalysts for Olefins Polymerization: an Understanding of Specific Activity Booster
Metallocene catalysts are the latest addition to the olefin polymerization catalyst family. They are homogeneous catalysts that usually require activation by specific species. Furthermore, metallocene catalysts need to be supported to be used at an industrial scale in gas or slurry phase processes and avoid reactor fouling. The advantage of such single-site catalysts is the ability to produce polymers with a very narrow molecular weight distribution (MWD) and the possibility of tailoring the polymer microstructure [1-2]. However, the main disadvantage of these catalysts is the high catalyst cost per ton polymer produced, mainly due to the cost of the activator and metallocene species combined with relatively low catalyst activity.
The support plays an important role in the overall activity of the catalyst. In fact, one of the ways to improve the metallocene catalyst activity is to tune support’s properties. This project aims to a thorough investigation of the support role in the polymerization reaction catalyzed by metallocenes, in order to understand the mechanism behind the significant increase in activity when employing specific modified supports.
The interaction between these modified supports, activator and metallocene will be studied by different spectroscopic techniques, such as UV-Vis-NIR, IR and Raman spectroscopy. The goal is to understand the role of the modified supports in the activation efficiency of the catalyst.
Furthermore, support fragmentation occurs during the reaction and, as the polymerization proceeds, the support fragments are dispersed within the growing polymer. It is hypothesized that these modified supports lead to an easier fragmentation, positively affecting the activity of the catalyst. To investigate the matter, the support fragmentation in the early stages of the reaction will be followed by both lab-based techniques (such as confocal fluorescent microscopy, UV-vis micro-spectroscopy, SEM-EDX) and synchrotron-based techniques (STXM and TXM).
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 W. Kaminsky, J. Chem. Soc., 1413-1418 (1998)