Similarities and Differences of the Active Sites in Basic and Advanced MgCl_2-Supported Ziegler-Natta Propylene Polymerization Catalysts

摘要

Though preparation procedures of heterogeneous Ziegler-Natta catalysts for propylene polymerization are sophisticated, it is uncertain whether the nature of the active sites is similar or different for different preparation procedures. In this study, the effects of prep-rnaration procedures on the nature of the active sites were investigated by stopped-flow polymerization in combination with microstructure analysis of polymers. Both basic and advanced types of catalysts showed the same two kinds of isospecific active site, which indicated little influence of the preparation method on the active site structure. On the contrary, the ratios of the two kinds of isospecific sites were not the same, resulting in variation of average polymer properties.