Propylene Polymerization Performance of Isolated and Aggregated Ti Species Studied Using a Well-Designed TiCl(3) /MgCl(2) Ziegler-Natta Model Catalyst

Abstract

In propylene polymerization with MgCl(2) -supported Ziegler-Natta catalysts, it is known that the reduction of TiCl(4) with alkylaluminum generates Ti(3+) active species, and at the same time, leads to the growth of TiCl(x) aggregates. In this study, the aggregation states of the Ti species were controlled by altering the Ti content in a TiCl(3) /MgCl(2) model catalyst prepared from a TiCl(3) · 3C(5) H(5) N complex. It is discovered that all the Ti species become isolated mononuclear with a highly aspecific feature below 0.1 wt.-% of the Ti content, and that the isolated aspecific Ti species are more efficiently converted into highly isospecific ones by the addition of donors than active sites in aggregated Ti species.