Synthesis Of Unsymmetrical Multidentate Phenolate Titanium Complexes And Their Catalytic Application In Ethylene Polymerization

Two parts were included in this dissertation:1) synthesis and characterization of unsymmetrical multidentate phenolate titanium complexes;2) study of the catalytic behavior of these complexes for ethylene polymerization.Totally four new ligands L1-L3and L8, five unsymmetrical multidentate phenolate titanium complexes C2, C5-C8, were synthesized in this dissertation, all of them were characterized by1H NMR,13C NMR and EA. The molecular structure of C5was further determined by X-ray diffraction method.All the five new titanium complexes were studied for ethylene polymerization. When activated with MAO, the titanium complexes showed moderate activities. When the polymerization temperature was50℃, time was30minutes and Al/Ti molar ratio was1000:1, complex C5displayed the highest activity of4.04×105g PE/(mol-Ti·h). The influence of polymerization conditions such as polymerization temperature, polymerization time and Al/Ti molar ratio on catalytic performance was also investigated. All the complexes obtained the highest activity at50℃except for C8. The activity increased when the Al/Ti molar ratio was increased from500:1to1000:1, but decreased when the Al/Ti molar ratio was futher increased to2000:1. What’s more, the activity increased when the polymerization time was increased from15minutes to30minutes, but decreased when the time was futher increased to45minutes. In addition, the activities of these catalysts were closely related to the steric structure and electronic effect of the complexes. The molecular weights of obtained polymers varied from0.49～25.2×104g/mol. The highest molecular weight of25.2×104g/mol was obtained by complex C7under the conditions of50℃,30min,5bar and Al/Ti=1000:1.