Ethylene trimerisation catalyst based on substituted cyclopentadienes Original Research Article

A four-component homogeneous catalyst system comprising a substituted cyclopentadiene ligand, a chromium compound, an alkyl aluminium and a halogen source is effective for the trimerisation of ethylene to 1-hexene in good selectivity and activity. In a typical example a catalyst system containing chromium(III) tris (2-ethylhexanoate), 1,2,3,4,5-pentaphenylcyclopenta-1,3-diene, hexachloroethane and triethylaluminium produced 1-hexene in up to 76 mass%, at an activity of 40 700 g of product/(g Cr h). Approximately 15 mass per cent of internal hexenes are also produced as well as smaller quantities of C-10’s and polyethylene. The effect of changes in temperature, pressure and reagent ratios has been investigated as well as the use of other substituted cyclopentadienes.