| Iso-polypropylene, which is well recognized as economically attractive and environmental friendly polymeric materials, has been applied in extensive fields. The key to the development of polypropylene is the renovation of catalysts. The latest generation of Ziegler-Natta catalysts takes on character of controlling the morphology of polymer particles. The resultant polymer with spherical morphology could be used in process directly without being pelleted. However, most of the preparation methods of spherical catalyst were introduced in patents. The polymerization mechanism is still not clear due to the complexity of the catalysts system; especially the specific role of the internal donors and external donors is still open to discussion. In this thesis, we have prepared spherical MgCl2 adducts supports for the spherical Ziegler-Natta catalyst using an improved method and investigated the preparation conditions of the support and the catalyst systematically; the obtained spherical catalysts were used in propylene polymerization and the properties of the catalysts and the behavior of the propylene polymerizations were also investigated.Through adding alcohol in batches and dispersing MgC^'EtOH at two steps we prepared spherical MgClj-nEtOH (n= 1.5~3.0) adduct supports. The effects of dispersion speeds and dosages of ethanol on the particle size and particle size distributions were discussed systematically. It was found that the particle size and particle size distributions of the spherical MgCl2 were mainly controlled by the dispersion speed. If matching the pre-dispersion speed and the dispersion speed better, the spherical particles can be obtained at lower dispersion speed. The content of the alcohol in supports could affect the property of the catalysts. Removal step of ethanol is needed when excessive EtOH was contained in the supports. In our experiments, the content of EtOH inresultant supports is lower and removal step of ethanol can be omitted. We found more favorable conditions for preparing good spherical MgCl2 supports for the spherical catalysts are: EtOH/MgCl2=3.0, the dispersion speed: 800-2000 rpm.The catalysts were prepared through treating the spherical supports with excessive TiCl4 directly in the presence of internal donors. The loading times of TiCl4 and the dosage of the internal donors made distinctive effects on the Ti content loaded in the resultant catalysts. Kind of phthalate and dosages of internal donors also affected the morphology of the catalyst obtained. IR spectra of catalyst showed that the chemical structure of the donors also affect the coordination among donors, Mg and Ti.In this thesis, the propylene polymerization using the obtained spherical catalysts was investigated. We found that different catalyst systems had different polymerization behavior at differentpolymerization temperature and AlEts/Ti. Internal donors and external donors in the catalyst system can affect the performance of the catalyst and the microstructure of resultant polymer. Diisobutyl phthalate (DIBP) with proper structure could complex with Mg, Ti in catalyst steadily, so high isotacitc polypropylene could be obtained. It was found that diphenyldimethoxysilane (DPDMS) was the best one used as external donors among the silanes. We also found that the textures of the catalysts related to the polymerization kinetics drastically. Some catalyst systems made the polymerization velocity fluctuant with the polymerization time, which is possible to indicate that new active species were formed during polymerization process. In addition, copolymerization of propylene and 1-hexene was also studied. We found that the activity of copolymerization of propylene and 1-hexene was higher than that of homopolymerization of propylene.
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