Ziegler-Natta Catalysts Preparation And Its Performance On The Olefins Polymerization

In this dissertation, we have prepared new Ziegler-Natta catalysts and studied theirperformances on the1-butene and ethylene polymerizations. Based on the characterizationof polymer, the relationships between structures of catalysts and performance of polymerswere studied in detail. The main results were summarized as follows:We have prepared a new MgCl2-supported preparation method in light of1-butenestructural characteristics. Main focuses were paid on the performances of Ziegler-Nattacatalyst modified by BCl3solution. The optimum preparation of catalysts has beeninvestigated by orthogonal experiment. The activity is2.43×104g/gTi for Ziegler-Nattacatalyst unmodified by BCl3while the activity is3.35×104g/gTi for modified Ziegler-Nattacatalysts. Furthermore, the effects of BCl3on the polymerization were studied for the slurrypolymerization and bulk polymerization, respectively. It was found that the activityincreased at low loading and then decreased after the addition of more BCl3. Theisotacticity, melting point, degree of crystallization performance declined slightly with theincreasing of the loading BCl3.The role of nucleating agent in the bulk polymerization and phase transformation wasstudied. It was found that the resulting poly(1-butene) obtained has higher the melting point,the degree of crystallization and phase transformation rate compared with the productwithout nucleating agent. The phase transformation rate varied with the kinds of nucleatingagent. The rare-earth nucleating agent, aryl-substituted phosphates and the sorbitol canspeed up the phase transformation, while amides and aryl carboxylic acid salts nucleatingagents has negative effect on the rate of phase transformation.A kind of SiO2/MgCl2supported Ziegler-Natta was prepared for the gas phasefluidized bed process of polyethylene. The effects of complex support preparation andprocess of the loaded-Titanium on the catalytic behaviors were investigated.We found thatthe alcohol compound prepared is the most critical factor, followed by the mass ratio ofSiO2and MgCl2. The reaction temperature between SiO2and MgCl2during the preparationof the complex support has slight effects on the catalyst performance. The impact of theTiCl4volume and the load temperature on the performance of the catalyst have also beenstudied. The optimum conditions for the preparation of the catalyst were obtained, that is, the molar ratio of alcohol to the MgCl2is3, the react time is2.5hour; the mass ratio SiO2to MgCl2is1, the reaction temperature is90oC, the optimal load-Titanium temperature is20oC and the volume of TiCl4is4mL/(g support).