MCM-41/ansa-zirconocene supported catalysts: Preparation, characterization and catalytic behaviour in ethylene polymerization

An MCM-41 has been modified by grafting several zirconocene complexes to give new materials potentially active in the polymerization of α-olefins. These materials have been activated by the cocatalyst MAO, to generate the catalysts MCM-41/metallocene/MAO (metallocene = [Zr(η5-C5H5)2Cl2] (1), [Zr{Me2Si(η5-C5Me4)(η5-C5H4)}Cl2] (2) and [Zr{Me2Si(η5-C5Me4)(η5-C5H3But)}Cl2] (3)). The resulting functionalized ordered mesoporous silica samples (1–3) were tested as catalysts in the polymerization of ethylene and compared with both the homogeneous system analogues and the functionalized silica derivatives SG/metallocene/MAO (SG = silica gel; metallocene = [Zr(η5-C5H5)2Cl2] (4), [Zr{Me2Si(η5-C5Me4)(η5-C5H4)}Cl2] (5) and [Zr{Me2Si(η5-C5Me4)(η5-C5H3But)}Cl2] (6)). The metallocenes 2 and 3 have been characterized by 13C-CP MAS NMR and 29Si MAS NMR spectroscopy. The structure and surface properties of MCM-41/[Zr{Me2Si(η5-C5Me4)(η5-C5H4)}Cl2] and MCM-41/[Zr{Me2Si(η5-C5Me4)(η5-C5H4)}Cl2]/MAO systems have been studied by X-ray diffractometry, nitrogen adsorption–desorption isotherms measurement and thermogravimetry. The grafting of the metallocene complexes, activation with MAO and subsequent polymerization reaction have been followed by an FT-IR “in situ” study. Scanning electron microscopy and transmission electron microscopy have been used to show the morphology of the heterogeneous catalysts as well as the resulting polyethylene obtained.

The preparation and structural characterization of ansa-zirconocene complexes supported on MCM-41 is described. The behaviour of these supported catalysts in the polymerization of ethylene has been studied and compared with their silica gel analogues.Figure optionsDownload as PowerPoint slide