| 1-Octene is impotant chemical product and intermediate. It is widely used as a co-monomer for polyethylene, intermediats for plasticizer, fatty acid, detergent alcohols and oil dope. There is no commercially successful process for tetramerizing ethylene to 1-octene specially. So the development of the catalyst and techniques of synthesis 1-octene by ethylene tetramerization with patented right seems especially important and urgent.According to the mechanisms of ethylene tetramerization, we have designed a novel trinuclear diphenylphosphinoamine ligand and studied nine cocatalysts with it in PNP/Cr(III)/cocatalyst catalytic systems. The studies focus on the 1-octene selectivity and catalyst activity. When methylaluminoxane (MAO) is used as cocatalyst, we can get the best results. Therefore, further detailed investigations have been carried out while changing the catalytic parameters with cocatalysts of MAO.Detailed studies on the catalytic performance of novel trinuclear diphoshinoamine ligand with MAO used to ethylene tetramerization are carried out, especially on the effect of reaction temperature, ethylene pressure, Al/Cr molar ratio on the activities and selectivities. The products have been characterized by gel permeation chromatography (GPC) and differential scanning calorimeter (DSC) to learn the performances of polymers containing the molecular weight, the molecular weight distribution and melting point.Catalytic datas show that this novel trinuclear diphenylphosphinoamine ligand with MAO used to ethylene tetramerization has not only high and long-life oligomerization activity, but also farely polymerization activity. The results show that oligomers were produced with high selectivity forα-olefins, especially 1-octene and 1-hexene, polyethylenes have low molecular weight (Mn) and broad molecular weight distribution. The average molecular weights (Mw) range from 1.5×105 to 4.6×105. The melting point ranges between 129 and 132℃. These values are in line with values given for MDPE.
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