Synthesis Of An Asymmetric Cobalt Imine Complex And Preparation Of Its Wide-distribution Polyethylene

In this thesis,we successfully synthesized a sequence of dissymmetr ic bis(imino)pyridine cobalt(II)chloride complexes(Co1-Co5),nameed[2-[CMe N{2,4-{(4-Me OC₆H₄)₂CH}₂–6-Me))-6-(CMe NAr)-C₅H₃N)Co Cl₂(Ar=2,6-Me₂-C₆H₃ Co1,Ar=2,6-Et₂Ph Co₂,Ar=2,6-i-Pr₂Ph Co3,Ar=2,4,6-Me₃Ph Co4,Ar=2,6-Et₂-4-Me Ph Co5),the catalytic performance of ethylene polymerization of all cobalt complexes were explored.The newly ligands and cobalt complexes were all tested and characterized by NMR,IR,ele mental analysis and X-ray diffraction.In the ethylene polymerization,Co balt complexes are very good pre-catalysts.Selecting of the polymerizati on conditions(the kind of cocatalyst,the dosage of the cocatalyst,the re action temperature,the reaction time and so on)is important for the cat alytic performance(the catalytic activity of cobalt compounds,molecula r weight,branching degree,and molecular weight distribution of polym ers).We also roundly analysed the relationship of the altering of the su bstituents and regulating of the polymers microstructure by high tempera ture gel permeation chromatography(GPC),high temperature nuclear mag netic and the differential scanning calorimetry(DSC).The following four chapters were covered:Chapter 1:Introduction.Chapter 2:Synthesis and characterization of all newly ligands com pounds(M and L1-L5)and bis(imino)pyridine 2-(2,4-bis(di(4-methoxyp henyl)methyl)-6-methylanilino)-6-(1-(arylimino)ethyl)pyridine-cobalt com plexes(Co1-Co5)were obtained using IR,¹H,¹³C NMR,elemental anal ysis and X-ray diffraction.Chapter 3:Investigation of the catalytic properties of these cobalt complexes to the ethylene polymerization by MAO or MMAO as cocatalysts.They all showed high activity(up to 10⁶ g·(PE)·mol^-1·(Co)·h^-1),and produced polyethylene with high molecular weight,high melting point and wide molecular weight distribution(22-62).In addition,the microstructure of the polymer was analyzed by high temperature NMR.We found that the change of substituents on the ligand had a great influence on the catalytic performance of cobalt complexes and the microstructure of polyethylene.By screening the kind of the cocatalyst,changing the reaction time and temperature,Co/Al molar ratio etc,to select the optimal polymerization conditions,the experimental data shows that MAO was selected as the cocatalyst,the polymerization temperature was 50?,the molar ratio of Al/Co was 3250,the running time was 30 minutes,and the polymerization catalytic activity was the highest.Using the complex Co1 as the precatalyst,the polymerization catalytic activity is 9.17×10⁶ g·(PE)·mol^-1·(Co)·h^-1.When MMAO is selected as the co-catalyst,the polymerization temperature was 50?,the molar ratio of Al/Co was 2750,the running time was 30 minutes,and the complex Co1 was used as the precatalyst to catalyze the polymerization of ethylene,the polymerization catalytic activity obtained is up to 7.00×10⁶g·(PE)·mol^-1·(Co)·h^-1.The most unique property of polyethylene prepared by this kind of cobalt complex system is the molecular weight distribution of polymer(22-62),which can be compared with that obtained by classical Phillips chromium catalyst(8-65)(M.P.Mc Daniel,advances in catalysis.2010,53),Although Phillips chromium catalyst has been considered to be able to leave a small amount of toxic chromium in polyethylene,it has been used for its good"shear dilution"and"melt strength".The asymmetric imine cobalt complex catalyst synthesized in this paper not only has similar unique properties,but also has no toxicity.This is the first time that cobalt complex can be used as catalyst for ethylene polymerization to produce polydispersity and high molecular weight linear polyethyleneChapter 4:Summary.