Abstract: A process for treating an aqueous phase obtained by acidic or basic washing of a hydrocarbon phase comprising a soluble aluminum compound in solution, characterized in that it is neutralized at a pH of from 6 to 8.5, treated with an additive selected from the alkaline-earth metal oxides, hydroxides and carbonates, at a temperature ranging from 90.degree. C. to the boiling point, the molar ratio of the additive to aluminum being from 1/10 to 10/1, and separated thereafter from the insoluble phase of precipitate.

Abstract: A process for oligomerizing olefins uses a catalyst composition obtained by contacting (a) bivalent nickel compound with (b) a hydrocarbylaluminum compound of the formula Al R.sub.x X.sub.y where R is a monovalent hydrocarbon radical, X is halogen, x is from 1 to 1.5, y is from 1.5 to 2, x+y being equal to 3, and (c) a Bronsted acid consisting preferably of a halogenocarboxylic acid of the formula R.sub.1 COOH in which R.sub.1 is a halogenoalkyl radical of the formula C.sub.m H.sub.p X.sub.q X being halogen, m an integer from 1 to 3, p being zero or an integer and q being an integer, the condition p+q=2m+1 being fulfilled. A preferred Bronsted acid is of the formula R.sub.2 COOH in which R.sub.2 is a halogenomethyl group of the formula CX.sub.n H.sub.3-n, X being halogen and n an integer from 1 to 3.

Abstract: An improved catalyst composition is obtained by contacting at least one bivalent nickel compound with at least one hydrocarbyl aluminum halide, at least one Bronsted organic acid and at least one anhydride of a carboxylic acid. The composition can be used as a catalyst for olefin oligomerization.