Study On The Effect Of Dendritic Metal Complex Structure On The Distribution Of Polymerizations

A new type of tert-butyl-substituted salicylald base-terminated PAMAM ligand wasprepared by1.0G PAMAM dendrimer with3,5di-tert-butyl-2-hydroxy-benzaldehyde. Thennickel chloride moieties were introduced onto the surface of ligands, which gave rise todendritic nickel compounds. The structures of dendritic ligand and its nickel complex werecharacterized by IR, NMR, UV, and elemental analyses. What’s more, the new nickelmetallodendrimer was evaluated as a catalyst precursor in the oligomerizations of ethylene,we also investigated the effect of catalyst structure of ligand on the olefin polymerization.The new nickel metallodendrimer was evaluated as a catalyst precursor in theoligomerization of ethylene, using Methylaluminoxane as an activator. The catalytic activityreached the maximum value4.93105(g mol-1Ni-1h-1) at0.5h,0.5MPa,25℃and Al/Niratio500for the nickel complex, the amount of C10-C18reached54.17%. The nature of thesubstituents on the benzene ring appeared to have a negative influence on the catalyticactivities of complexes and the main products was high carbon olefins. With more activesites, the dendrimer nickel compound has higher catalytic activities, but the amount of activesites have no influence on the distribution of products. Compared with salicylaldbase-terminated PAMAM nickel complex, pyridine-2-carboxaldehyde base-terminatedPAMAM nickel compound has higher catalytic activity and the products have highermolecular weight. With different structures of dendrimer nickel compounds, suitablecocatalyst could active the nickel compounds which are used in the o lefin polymerizations,the catalytic activity and the product dristribution depend on the kind of cocatalysts. As thegeneration increasing, the catalytic activity and selectivity increased and the more higherolefins obtained.A new hyperbranched salicylaldehyde-imine nickel complex was prepared andcharacterized via element analysis, ESI-MS, FT-IR, UV,1H NMR,13C NMR. Using MAO asan activator, the complex was evaluated as catalyst precursor in the oligomerization ofethylene and the effects of oligomerization conditions on the catalytic properties. The catalystpossesses a middle catalytic activity of5.59×105g/(mol Ni h) however with a selectivity forhigh carbon olefins of91.12%.