Characterization of stepwise prepared, silica supported zirconocene catalysts designed for olefin polymerization

Heterogeneous zirconocene catalysts were prepared with an unconventional method by grafting mesoporous silica SBA-15 fiber with ZrCl4 in gas or liquid phase and subsequently with lithium salt of cyclopentadiene (Cp) or indene (Ind). In order to obtain a better understanding of the bonding modes of the zirconium and the ligands, the ZrClx/SiO2 and ZrClxL/SiO2 were now for the first time characterized by several techniques, including elemental analysis, FTIR spectroscopy, 1H MAS NMR and 13C CP MAS NMR. The results verify the η5-bonding of the ligands to the metal center, which in turn was discovered to be both mono- and bifunctionally bonded to the silica. The catalysts were tested in ethylene polymerization, in which they yielded polyethylene with moderate activities.

Graphical abstractMesoporous silica fiber was treated with ZrCl4 and subsequently with LiCp or LiInd to produce a heterogeneous catalyst designed for olefin polymerization. Emphasis of the study was put on the characterization of the resulting ZrClxL/SiO2 structure with elemental analysis, FTIR and solid state 1H and 13C NMR, but the activity in the polymerization of ethylene was also tested. Figure optionsDownload full-size imageDownload as PowerPoint slide