Study On Synthesis,Characterization And Catalytic Properties Of Metal Zirconium/Hafnium Complexs By Bipyridindiol Bis (Phenolate) Ligands

As an organic polymer material that is widely used in the world,polyolefin has many advantages such as easy availability of raw materials,low price,easy production and processing,and good corrosion resistance.Due to its advantages in performance,polyolefins have been widely used in various fields such as food packaging,building materials,and electrical components in various countries around the world.Olefin polymerization catalysts play a decisive role in the morphology,structure and properties of polyolefins,and have received unanimous attention from the industrial and scientific circles.After decades of development,olefin polymerization catalysts have undergone continuous upgrading,from Ziegler-Natta catalysts in the 1950s to today’s non-metallocene catalysts.At present,countries around the world still have an increasing demand for polyolefins with special functions,so it is still of great significance to continuously develop new olefin polymerization catalysts.The second chapter of this thesis mainly introduces the experimental drugs and reagents used,as well as the instruments used to characterize ligands,complexes and polymers.The third chapter of this thesis uses p-tert-butylphenol and2,4-di-tert-butylphenol as raw materials.After a series of bromination with NBS,n-butyllithium lithiation,boronic acid,and Suzuki coupling reaction catalyzed by palladium,the coupling reaction followed by the addition of boron tribromide to remove the methyl group of the-OCH₃group finally obtained the ligands L1H₂ and L2H₂.Then,n-butyllithium is added to the toluene solution of the obtained ligand to generate a dilithium salt,and then drop into the toluene solution of zirconium/hafnium tetrachloride dropwise to react,so that a stable coordination bond is formed between the metal and the nitrogen atom on the pyridine ring,and O^-forms aσbond with the central metal,and complexes C1-C4 are synthesized.Then the complexes C1-C4were characterized by ¹H NMR and ¹³C NMR to confirm the structure.In the fourth chapter of this paper,under the activation of the cocatalyst MAO or AlⁱBu₃/Ph₃CB（C₆F₅）₄,catalysts with different structures are used to catalyze ethylene polymerization and ethylene/1-octene copolymerization,and finally obtain various properties of polymer.The results show that when catalyzing the polymerization of ethylene,with the cocatalyst MAO is used,the number of Al/M is 2000,and the polymerization temperature is 80°C,the polymerization effect is the best.The polymerization time was extended to 2.5 h,and it was found that the catalyst had a longer service life.The obtained polymer was characterized by DSC and high-temperature carbon spectrum,which showed that the sample was linear polyethylene.It was found that in the copolymerization reaction,when the concentration of octene was 3 m L,the polymerization activity was the largest;with the increase of the amount of octene,the molecular weight of the copolymer gradually decreased.After adding 1-octene,the catalytic activity is obviously higher than that of ethylene polymerization,the molecular weight of the polymer is decreased,and the melting point of the obtained polymer is also significantly decreased.In catalytic ethylene polymerization and catalytic ethylene/1-octene copolymerization,different catalyst structures obviously affect the properties of polymers,and the steric hindrance effect is the main reason for affecting the properties.