Synthesis Of Salicylaldimine Bimetallic Half-titanocene Catalysts And Olefin Polymerization Research

Polyolefins are currently the most important class of synthetic polymers with the largest production volume.Designing and synthesizing efficient catalysts for olefin polymerization and copolymerization is of great significance in academic research and industrial applications.Compared with monometallic catalysts,bimetallic catalysts will affect their polymerization activity,molecular weight and molecular weight distribution of polymers due to the synergistic effect between the two metal active centers.The salicylaldimine catalyst can also affect the catalytic performance of the catalyst by changing the steric hindrance and electronic effect of different substituents.This paper is mainly based on the preparation of binuclear half-titanocene salicylaldimine metal catalysts and the influence of polymerization conditions on the performance of the catalysts.Two catalysts with different metal center distances were designed and synthesized,and a single metal catalyst was synthesized as a control.Through different testing methods,such as nuclear magnetic resonance analysis and XRD-single crystal diffraction analysis,the synthesized ligands and metal catalyst structures were characterized,and the metal catalysts were tested for ethylene homopolymerization.Polymerization properties of copolymers of ethylene and 1-octene.The main work of this paper is as follows:1.Designed and synthesized three kinds of monosalicylaldimine and bisalicylaldimine ligands（mono-L,syn-L and anti-L）with anthracene as the skeleton,and then combined with pentamethylcyclopentadienetrimethyltitanium reaction,three corresponding monotitanocene catalysts 1-N-anthracenyl（salicylaldimidyl）pentamethylcyclopentadienetrimethyltitanium catalyst（Ti₁）,N,N’-1,8 anthracenylbis-[（salicylaldiene）pentamethylcyclopentadienetrimethyltitanium]catalyst（syn-Ti₂）and N,N’-1,5 anthracenylbis[（salicylaldimine）pentamethylcyclopentadienetrimethyltitanium]catalyst（anti-Ti₂）,and its structure was characterized by nuclear magnetic resonance（NMR）and XRD-single crystal ray diffraction and other testing methods.2.The catalytic performance of three metal catalysts for ethylene polymerization was explored.Under the condition of[Ph₃C][B（C₆F₅）₄]as cocatalyst,the effect of reaction temperature on the activity of three catalysts was compared.The results show that the catalytic activity is anti-Ti₂>syn-Ti₂>Ti₁ at 100°C,the optimum activity temperature of the catalyst anti-Ti₂ is 100°C,and the activity can reach 2.3×10⁷ g（PE）·mol^-1（Ti）·h^-1.The catalytic performance of three metal catalysts for the copolymerization of ethylene and 1-octene was investigated.With[Ph₃C][B（C₆F₅）₄]as the cocatalyst,the catalyst syn-Ti₂ has the best activity of 3.36×10⁷ g（POE）·mol^-1（Ti）·h^-1 at 50°C and the concentration of 1-octene is 0.5 M.With[Ph₃C][B（C₆F₅）₄]as cocatalyst,1-octene concentration of 0.5 M,and 50°C,the catalytic activity is Ti₁>anti-Ti₂>syn-Ti₂,and the activity of catalyst Ti₁ can reach 4.15×10⁷ g（POE）·mol^-1（Ti）·h^-1.