Dual-active-site nature of magnesium dichloride-supported cyclopentadienyl titanium chloride catalysts switched by an activator in propylene polymerization

Abstract

MgCl2-supported metallocene catalysts often show peculiar catalytic aspects, which are partially similar to both non-supported complexes and traditional Ziegler-Natta catalysts. In this study, the active-site natures of various MgCl2-supported cyclopentadienyl Ti chloride catalysts are systematically investigated and compared with traditional catalysts in propylene polymerization. The supported titanocene catalysts offer both metallocene-type and Ziegler-Natta-type active-site natures according to the details of the preparation and the activation procedures. The observed dual-active-site natures are plausibly correlated with the valence and charge states of the Ti center. The active-site natures of MgCl2-supported cyclopentadienyl Ti chloride catalysts are studied and compared with traditional Ziegler-Natta catalysts in propylene polymerization. The supported titanocene catalysts generate either metallocene- or Ziegler-Natta-type active sites, which are strongly affected by the reduction of Ti precursors by an activator. The dual-active-site nature of MgCl2-supported cyclopentadienyl Ti chloride catalysts is proposed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.