Studies On Synthesis, Characterization And Catalysis For Olefin Polymerization Of Novel Metallocene Catalysts And Ziegler-Natta Catalysts

Polyolefins are the largest volume synthetic materials used in the world, and have been almost applied in every aspect of our daily lives and productions. The growing demand for high performance polyolefin products in recent years has inspired extensive industrial and academic interest to develop high performance olefin polymerization catalysts. The discovery and application of TiCl₄/alkylaluminum/MgCl₂ catalyst systems have revolutionized the manufacturing industry. The extremely high activity and stereoselectivity of these catalysts have given rise to simplified, environmentally benign production processes and the formation of reasonably priced polyolefins with improved performance parameters. Moreover, it should be stressed that the use of MgCl₂-supported catalysts has enabled excellent control of the polymer morphology, due to the case with which MgCl₂-supported with controlled particle size and narrow particle size distributions can be prepared, and this has contributed significantly to the enhancement of polymer productivity. While these supported catalysts are the pillars of the polyolefin industry, because of the above-mentioned advantages, they are multisite catalysts consisting of many types of uncharacterized active sites that form polymers with broad distributions of molecular weight and chemical composition. Therefore, it is very difficult to precisely control the polymer microstructure and hence the properties of the resulting polymers when using these multisite catalysts. Though extensive and continuous efforts have been devoted to developing MgCl2-supported single-site TiCl4 catalysts, no sigle-site catalyst of this type has been reported thus far.Metallocene type catalysts can produce a variety of high performance polyolefin products, including isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, high density polyethylene, linear low density polyethylene, syndiotactic polystyrene, and cyclo-olefin copolymer. Despite the success of metallocene-based catalysts in catalyzing the above mentioned olefin polymerization reactions, they also exhibit disadvantageous features. A large amount of methylaluminoxane (MAO) or expensive fluorinated borate such as Ph3C+B(C6F5)4- is generally required as cocatalyst or activator for obtaining acceptable polymerization activity, which raises issues of the high cost of the metallocene type catalyst systems and the high ash content (Al₂O₃) of the product polymers. Consequently, there is a great need to develop new catalyst systems which can provide equivalent catalytic activity with no need of large amounts of expensive cocatalyst.Conclusions were summarized as follows:A series of chromium complexes Cp*Cr[2,4-^tBu₂-6-(CH=NR)C₆H₂O]Cl [R = tBu, Ph, 4-Me-C₆H₄, 2,6-Me₂C₆H₃, 2,6-iEt₂C₆H₃, 2,6-ⁱPr₂C₆H₃] were synthesized and characterized. Upon activation with a small amount of AlR3 [R = iBu, Et, Me], all complexes show reasonable to good catalytic activity for ethylene polymerization, producing polyethylene with high molecular weight. ¹³C NMR analysis on the polymer samples indicates that the polyethylenes produced by these catalysts are linear and have no branch.A series of chromium complexes CpCr[Ortho-C₆H₄NR₁(CH=NR₂]Cl [R₁, R₂ = Ph, , 2,6-Me₂C₆H₃, 2,6-iEt₂C₆H₃, 2,6-ⁱPr₂C₆H₃] were synthesized and characterized. Upon activation with a small amount of AlMe₃, all complexes show reasonable catalytic activity for ethylene polymerization.A series of chromium complexes Cp*Cr[2,4-tBu₂-6-(CH₂NR₂)C₆H₂O]Cl [R = Me, Et, iPr] were synthesized and characterized.A series of titanium complexes [2,4-tBu₂-6-(CH=NR)C₆H₂O]TiCl3 [R = iPr, tBu, nBu, Ph, 4-Me-C₆H4, 2,6-Me2C₆H₃, 2,6-iPr2C₆H₃]were synthesized and characterized. Upon combination with MgCl2 and AlMe3, all complexes show reasonable catalytic activity for ethylene polymerization.A series of titanium complexes Cp′Ti(2,4-tBu₂-6-(CPh₂O)C₆H₂O)Cl [Cp′=η5-C₅H₅,η5-C₅(CH₃)5,η5-C₅H₂Ph₂CH₃] were synthesized and characterized. Upon activation with [Ph3C]+[B(C₆F5)4]- and AliBu3, all complexes exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melt transition temperature. Addition of excess water to complex CpTi(2,4-tBu₂-6-(CPh₂O) C₆H₂O)Cl gave the oxo-bridgedcomplex [Ti(η5-C₅H₅)(2,4-tBu₂-6-(CPh₂O)C₆H₂O)]2O [CpTi(η2-(C,N)-2-ArNH-C₆H4C=NAr)Cl2] (Ar=2,6-iPr2C₆H₃) has been synthesized and characterized by elemental analysis, NMR spectra, and single crystal X-ray diffraction...