Preparation and Catalytic Performance of Silica-Supported Cr(acac)3/PNP for Ethylene Tetramerization

Chromium acetylacetonate and bis(diphenylphosphino)isopropylamine were coordinated in situ and supported on methylaluminoxane-modiifed silica. The catalyst structure and effects of reaction temperature, reaction pressure and Al/Cr molar ratio on ethylene tetramerization were investigated in detail. Chromium was uniformly and ifrmly immobilized on the support and could not be leached off by methylaluminoxane. The supported catalyst, upon being activated with methyl-aluminoxane, exhibited catalytic activity of 1.70×107 g/(mol Cr·h) for ethylene tetramerization to form 1-octene at a reaction temperatures of 80℃, a pressure of 2.0 MPa and an Al/Cr molar ratio of 300. The supported catalyst presented a good toler-ance to high temperature.