Polymerization of Ethylene Using α-Diimine Nickel Catalyst

The late transition metal catalysts based on end group of transition metals in the periodic table like Ni, Fe, Co, Pd, Pt were developed rapidly in polyolefin industrial productions. These metals with suitable ligands exhibited specific properties and appropriate activities in the production of polyolefins. These catalysts based on bulky bisimine ligands usually depend on the structures of the ligands and the ortho group position on the aryl ligands show very interesting behaviors in olefin polymerization. When these groups, located in the ortho positions of aryl ligands, become larger, it would have lesser chance in leading to β hydrogen elimination reactions. The ligand 1,4-bis (2,6-diisopropyl phenyl) acenaphthene was synthesized by reaction of 2,6- diisopropyl aniline and acenaphthene quinone. The synthesized ligand was then added on nickel (II) dibromide salt that produced the 1,4-bis(2,6-diisopropyl phenyl) acenaphthene nickel (II) dibromide catalyst. The structure of the catalyst was fully characterized by IR, NMR techniques. Ethylene polymerization was performed using the prepared catalyst and the effects of parameters such as, polymerization temperature, cocatalyst, to catalyst molar ratio and monomer pressure, were investigated. One of experimental design methods (Box Behnken) was used to minimize the number of tests. The highest activity of catalyst [1420 kgPE/molNih] was obtained at monomer pressure 5 atm, [Al]:[Ni] = 1000 and polymerization temperature of 25°C. Some of the produced polymers were characterized by DSC and 13CNMR. The branched structures with higher methyl branch contents were observed in some polyethylene products.