New strategy for Attachment of α-DiimineNickel(II) Catalysts on Supports For Ethylene Polymerization with Controlled Morphology

A novel spherical MgCl2 supported α–diiminenickel(II) catalysts for ethylene polymerization in slurry phase is Prepared.α–Diimine ligands were synthesized by condensationreaction of 2,6-disubstituted alkyls or aryls anilines and acenaphthenequinone which have hydroxyl functionality intheir para-position. Hydroxyl functionalized α–diiminesshowsstrong attachment on to the spherical MgCl2 support by dative bonding. No linker was needed to attach the complexes ontothe support surface and the amount of Nickel loading was controllable to improve morphology and specially bulkdensity of polymer powder. A significant reduction in catalysts activity was observed when homogeneous catalysts were supported onto silica but this reduction was decreasedwhen they were supported onto thermally treated spherical MgCl2. As homogeneous Bis(N,N’-(4-(3-hydroxyl-propyl)-2,6-di[(4-tert-butyl-phenyl)-phenyl) imino]acenaphthene Nickel dibromide(d) showed the highest activity among other evaluated homogeneous catalysts, its MgCl2 supportedcatalyst (d /S-MgCl2) has shown the highest activity among MgCl2 supported catalysts too. These MgCl2 supportedcatalysts were prepolymerized in presence of ethylene monomer in the mild polymerization condition to yield prepolymerized catalyst with polymer/catalyst weight ratioequal to six. Spherical polyethylene particles without reactor fouling were obtained by these prepolymerized catalysts.Clearly, shown in SEM images that the spherical morphology of MgCl2 support is replicated in the produced polymer. Themolecular weight and molecular weight distribution of produced polymer with MgCl2 supported catalysts were higher than those produced by homogeneous catalysts.