The Synthesis, Characterization Of A Series Of Self-immobilizing FI/Zr Catalysts And The Study Of Their Catalytic Properties For Olefin Polymerization

At industrial, the traditional heterogeneous catalysts are expected to remain thedominant catalytic route for the production of poly-olefins mostly owing to therequirement of inorganic or organic supports to directly get polyethylene withspherical morphology in the slurry process during which such controlled particlegrowth eliminates reactor fouling and polymer particles whose shape mirrors thestarting catalyst particles. As is known to all, Ziegler-Natta catalyst is a kind offrequently-used heterogeneous catalyst to make polymer particles. But the catalyticactivity is limited. In order to improve the catalytic activity,metallocene/methylaluminoxane and late transition metal catalytic systems areproduced Meanwhile the phenoxy-imine (FI) catalysts displayed very high ethylenepolymerization activities, so they were extensively investigated in the olefin(co)polymerization processes. Significant efforts have been made to develop newmethod to immobilize FI catalysts in resent years. Silica, silica-alumina derivativesand MgCl2were respectively used as support to immobilize the homogeneous FIcatalysts. Ethylene polymerzation with such supported catalyst system gave polymerswith higher molecular weight, higher melting temperature and better morphology thanthose obtained with the corresponding homogeneous catalyst. Notably, Fujitadeveloped a supported catalysts which combined with MgCl2/RˊnAl(OR3)3-nas asupport. While compared to the corresponding homegeneous catalysts, the supportedcatalysts demonstrated superior catalytic properities, in terms of their catalytic activitymolecular weight, stereoselectivity, comonomer incorporation and morphology.However, more often than not, the complex process of the loading and low catalystloadings of the supported catalysts makes it limitation to develop further. Moreover,Alt et al. developed a strategy, which means to synthesize catalysts with an olefin oralkyne function that can be used as a comonomer in the polymerization process, henceforming the self-immobilization catalysts. Jin group reported several sefl-immobilizedtitanium and zirconium FI catalysts with allyl substituted phenoxy-imine ligands, withwhich a high activity for ethylene polymerization and an improved polymer particlesmorphology was obtained. While K.MULLEN groups pointed out that polystryrenelatex particles with nucleophilic substituents on the surface can also act as a carrier fortitanium FI-catalyst to produce poleyethylene with considerable activity, as long as6 h catalytic lifetime and ultrahigh molecular weight. In this work, we exploited a newway to heterogenize the homogeneous FI catalysts. The metal-organic coordinationpolymers generated by self-immobilizing of multitopic ligands with metal ions as theheterogeneous catalysts developed by us might provide a concise and effective way toproduce polymer particles with better morphology. Self-immobilizing catalysts havemany advantages such as relatively easy immobilization technique, no supportnecessary and high density of active catalyst centers. Several self-immobilizingheterogeneous catalysts were synthesized by using multitopic Schiff-base ligandprecursors thus simulating self-immobilizing FI catalysts. A series of polymerizationwith these self-immobilizing catalysts activated with AlR3only or activated with AlR3and Ph3CB(C6F5)4together were conducted. The results showed that the catalystshave a certain catalytic activity for ethylene polymerization and copolymerizationwith1-hexene.Moreover the spherelike particles polyethylene products were obtained.