Abstract: A process for producing a partially sulfurized nickel catalyst is disclosed wherein a pre-reduced nickel catalyst comprising nickel having a crystallite size of between about 10 and about 200 A is treated with at least one organic sulfur compound selected from the group consisting of thiophene, alkylthiophenes and mono-, and disulfides and mercaptans, at a temperature of between about 75.degree. and about 200.degree. C at a sufficient hydrogen pressure and for a period of time sufficient to produce a partially sulfurized nickel catalyst containing from about 1.5 to about 8 parts by weight of sulfur per 100 parts by weight of nickel.

Abstract: A catalytic system for oligomerizing olefins comprising (1), an aluminum compound of formula Al(R).sub.n X.sub.3-n or a mixture of such compounds, wherein R is a straight chain or branched alkyl radical containing from 2 to 18 carbon atoms, n is 1, 2 or 3 and X is a halogen, (2), an organic complex of a metal of Group VIII of the periodic table, and (3), a promotor comprising a compound of formula R'X wherein R' is a straight chain or branched alkyl radical containing from 3 to 12 carbon atoms, substituted or unsubstituted, and X is a halogen, the molar ratio of promotor to aluminum compound being between 0.05 and 20.