Salicylaldehyde Imine-pyrrole Imine Ti(?) Catalysts For Ethylene Polymerization

With the wide application of polyolefin materials,the consuming demand is increasing day by day.In this thesis,two novel ligands were synthesized to obtain polyolefin transition metal catalysts with novel structures and unique catalytic properties.First,by ligand structure design,pyrrole imide and salicylaldehyde imine ligands was synthesized,after reacting with the former transition metal Ti(?),the salicylaldehyde imine titanium complexes and salicylaldehyde imine-pyrrole imine titanium mixed ligands titanium complexes were prepared.The obtained complexes were applied to ethylene polymerization,and the effects of catalyst structure and ethylene polymerization conditions on catalytic activity,molecular weight and distribution of polymerized products were studied and analyzed.The specific research contents of this paper include:1.Synthesis of pyrrolidine ligands: as a precursor,2-acetylpyrrolidine reacted with six different substituted aromatic amines by Schiff-base condensation under microwave radiation to synthesize six pyrrolidine imine ligands.2.Synthesis of salicylaldehyde imide ligands: as a precursor,salicylaldehyde reacted with four aromatic amines with different substituents by Schiff-base condensation under microwave radiation,and four corresponding salicylaldehyde imide ligands were obtained.By comparing the reaction rates and yields of ligands with different substituents,the effects of substituent types on the reactivity of ligand synthesis were studied.3.The synthesis of titanium complexes: the reaction of salicylaldehyde imine ligands with Ti(?)salt generated the corresponding single ligand complexes;the complexing reaction of Ti(?)salt with salicylaldehyde imine and pyrrole imine ligands at the same time,generated the mixed ligand complexes.4.Composition and structure analysis of ligands and complexes: the pyrrole imine ligands,salicylaldehyde imide ligands and the corresponding titanium metal complexes were comprehensively characterized by means of melting point,elemental analysis,infrared analysis,ultraviolet analysis,thermogravimetric analysis and other characterization methods,to prove the composition and structure of ligands and complexes.5.Research on catalytic performance of ethylene polymerization: the titanium complex obtained was used as the main catalyst and MAO as the co-catalyst to study the influence of ligand species,steric hinderance,electronegativity and other factors on catalytic activity.The results showed that when the substituent group was an electronabsorbing group,the number of polymerization coordination centers increased and the catalytic activity of the catalyst was enhanced.The catalytic activity of the substituents in the ortho position was higher than that in the para and meso position.When the substituents were in similar positions,the increase of the number of substituents would increase the catalytic activity of the catalyst in ethylene polymerization.In addition,the effects of time,temperature,ethylene pressure,n(Al)/n(M)and other reaction conditions on the catalytic performance of ethylene polymerization were investigated.Found by experiments,it is concluded that the best polymerization reaction conditions are as follows: reaction temperature 40 ?,ethylene pressure 1 Mpa,n(Al)/n(M)1500,the reaction time of 1.5 h.