Catalysts and conditions for the highly efficient, selective and stable heterogeneous oligomerisation of ethylene Original Research Article

The oligomerisation of ethylene into products in the C4–C20 range over heterogeneous nickel catalysts in a fixed-bed reactor at low temperature and high pressure (LT-HP) is reported. The catalysts were obtained by Ni(II) exchange or impregnation of two differently prepared amorphous and mesoporous silica–alumina supports. A plot of catalytic activity versus temperature at 35 bar and MHSV=2 produces a volcano-type curve with a maximum around 120°C. Experiments performed under the LT-HP reaction conditions, viz. 120°C, 35 bar and MHSV=2, give an ethylene conversion level of 99% and a 97% selectivity to products with an even number of carbon atoms. The product spectrum (Cn distribution) was dependent on the type of catalyst used, with the percentage of the C10+ oligomers lying in the range 23–41% by mass. Of practical significance, these types of catalyst were found to be extremely stable in use showing no detectable drop in conversion after 108 days on stream under the LT-HP reaction conditions employed.