Active site nature of magnesium dichloride-supportedtitanocene catalysts in olefn polymerization

Heterogeneous Ziegler-Natta and homogeneous metallocene catalysts exhibit greatly different active site nature in olefn polymerization. In our previous study [1], it was reported that MgCl2-supported titanocenecatalysts can generate both Ziegler-Natta-type and metallocene-type active sites according to the type of activators.The dual active site nature of the supported titanocene catalysts was further explored in the present study: Theinfluence of the ligand structure of titanocene precursors was studied on the nature of active sites when supportedon MgCl2 in ethylene and propylene homopolymerization, and ethylene/1-hexene copolymerization. It was foundthat the reducibility of titanocene precursors by alkylaluminum is closely related to the appearance of the dualactive site nature, while the kind of olefn did not affect the type of active sites formed during polymerization. TheZiegler-Natta-type active sites produced poorly isotactic polypropylene and less branched polyethylene, while themetallocene-type active sites produced atactic polypropylene and exhibited much higher incorporation effciencyfor 1-hexene. Polyolefns J (2015) 2: 57-63

کلیدواژه ها:

metallocene catalysts ، Ziegler-Natta polymerization ، poly(propylene) (PP)