NICKEL-BASED HETEROGENEOUS CATALYSTS FOR OLEFIN OLIGOMERIZATION .1. SUPPORT AND ANION EFFECTS

Using the pore-filling method, a series of catalysts was prepared by impregnation of various inorganic oxides (silica, alumina and silica-alumina) with aqueous solutions of nickel nitrate, sulfate or chloride. Calcination in air at 500°C completely decomposed the nitrate ions and partially removed the chloride ions, whereas the sulfate ions remained entirely in the catalysts. The catalysts thus pretreated were tested in the liquid-phase oligomerization of propene at 40°CC and a pressure of 0.4 MPa. The catalysts derived from nickel nitrate deposited on silica or alumina exhibited no activity, whereas all the others were active. The NiCl2/Al2O3 catalyst turned out to be the most active and selective. The influence of the nature and the amount of associated ions (sulfate, chloride) on the activity and selectivity for propene oligomerization was investigated and their role is discussed in terms of support acidity.