Effects of Electron Donors on Active Sites Distribution of MgCl2‐Supported Ziegler‐Natta Catalysts Investigated by Multiple Active Sites Model

Summary: The stopped‐flow polymerization of propylene catalyzed by a Ziegler‐Natta catalyst in the presence of internal and external electron donors was carried out. The influence of the electron donors on the active sites of the catalyst was investigated using a multiple active site model. The variation of each group of active sites, such as the concentration and kp of each site at various polymerization times, can be obtained from this model. It was found that an electron donor mainly affects the aspecific active site by reducing its concentration and increasing its kp. The isospecific site is only slightly altered in terms of concentration and its kp because of steric hindrance. Variation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times. image Variation of [C*] of each active site of TiCl4/MgCl2‐AlEt3 at various polymerization times.