Studies On Olefin Polymerization Catalyzed By Metallocene/Cocatalyst (Containing Boron Compound) Catalytic System

Metallocene catalysts have attracted both academic and industrial attention in recent 20 years. Cocatalysts, often in the form of main-group organometallic compounds in traditional two-component Ziegler-Natta catalytic systems, have also played a very important role in the single-site polymerization. But the study on co-catalyst (containing boron compound) is limited, so this dissertation focuses on the study of boron compound co-catalyst, such as the modification of MAO (methylaluminoxane) using halogen boron compound; the modification of inorganic oxide support using halogen boron compound, together with its usage for supporting metallocene catalyst, and catalytic behavior of resultant catalyst for ethylene polymerization. Ethylene polymerization and the copolymerization of ethylene-a-olefin with metallocene/AlR3/B(C6F5)3 catalytic system were also investigated.For the first time, this paper systematically studied the modification of MAO using halogen boron compound. It was found that the activities of ethylene polymerization catalyzed by metallocene/boron modified MAO catalytic system were higher than those catalyzed by metallocene/MAO, which relate to the ability of accepting electron by boron and the formation of [Cp2ZrCH3]+[B-MAO]~ for the Cp2ZrCl2/B-MAO catalytic system. According to the kinetic characterization of the ethylene polymerization and the consideration of reactivate of deactivate site, a novel and reasonable kinetic model is presented. Simulating results using the model are consistent with experiment results, which indicate that the model including reactivate of deactivated species is reasonable.The supported metallocene catalyst has many advantages compared with homogeneous metallocene catalyst, so it is of great theoretical significance and practical value to find new supports and new modifying methods. Carriers such as SiO2, A12O3 were modified by halogen boron. It was found that the modificationconditions such as the pretreatment temperature of the carrier, the reaction time and the added concentration of BF3 have more effect on the amount of BF3 deposited on the SiO2, Al2O3 support surface. The amounts of the hydroxyl on the support surface decrease with the increasing calcined temperature. SiO2, A12O3 were modified by BF3 through chemical reaction between hydroxyl and BF3, as well as physical absorption of BF3. The supported catalyst Cp2ZrCl2/BF3/SiO2 was prepared and used for ethylene polymerization and new methods for determination of Zr contents on supported catalyst was developed. The results show that the resultant supported catalyst gives a well-performing catalytic properties and the polymerization activity can reach to 106gPE/mo]Zr.h even at low Al/Zr mole ratio. The new modification methods and the new type supported catalyst possess of potential commercial value.Metallocene/B(C6F5)3 catalytic system has advantages in some way compare with metallocene/MAO catalytic system. Unfortunately, the former catalytic system requires dialkylmetallocene which is difficult to synthesize, to store and to transfer. A novel catalytic system dichlorometallocene/AlR3/B(C6F5)3 is developed. However very low activity and no activity was observed when AlEt3 used, and high activity was obtained when Al(iBu)3 was used at proper Al/Zr mole ratio. A plausible mechanism is presented to interpret the ethylene polymerization activity changes with the different Al/Zr mole ratio when Al(iBu)3 used. The interaction between active center and Al(iBu)3 can be detected from UV-visible spectroscopy and ESR spectra.Copolymerization of ethylene/a-olefm with metallocene/Al(iBu)3/B(C6F5)3 catalystic system was also investigated. The copolymerization activity changes with the different a-olefin type used and the a-olefin feed concentration. In the case of hexene, the activity is increased at low comonomer concentration range and after that decreased. As for dodecene and hexadecane, the copolymerization activity largely decreased due to their stereo effect.The molecular weight of ethylene/hexene...