Effects of electron donors on active sites distribution of MgCl2-supported Ziegler-Natta catalysts investigated by multiple active sites model

The stopped-flow polymerization of propylene catalyzd by a Ziegler-Natta catalyst in the presence of internal and external electron donars 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 K-p of each site at various polymerization times, can be obtained from this model. It was found that an electron donar mainly affects the aspecific active site by reducing its concentration and increasing its k(p). The iso-specific site is only slightly altered in terms of concentration and its k(p) because of steric hindrance.