Ethylene oligomeration

Claim 1

An improved process for the oligomerization of ethylene comprising contacting said ethylene with a catalyst composition in the liquid phase present in at least one solvent selected from the groups consisting of: (i) an aromatic hydrocarbon of the formula ##STR11## wherein R"' represents a C 1 to C 6 alkyl radical and n is 0, 1, 2, 3, or 4; (ii) an alcohol of the formula (R iv ) 3 COH wherein R iv independently represents H or a C 1 to C 12 alkyl, cycloalkyl, aryl, alkaryl, or aralkyl radical with the proviso that at least one R iv is not hydrogen; (iii) an amide of the formula ##STR12## wherein each R v independently represents H or a C 1 to C 10 alkyl, cycloalkyl, aryl, aralkyl, or alkaryl radical with the proviso that at least one R v is not H; (iv) a C 2 to C 20 ether; (v) a C 2 to C 20 ester; (vi) a C 3 to C 20 ketone; (vii) a C 2 to C 20 nitrile; and (viii) a C 6 to C 20 chlorinated aromatic, the catalyst consisting essentially of: (a) at least one nickel compound selected from the group consisting of: bis(1,5-cyclooctadiene)nickel(O); bis(tricyclohexylphosphine)nickel(O); nickel tetracarbonyl; (cyclododecatriene)nickel; and bis(ethylene)(dicyclohexylphosphine)nickel; (b) a phosphine compound of the formula PR 3 wherein R independently represents H or a C 1 to C 20 hydrocarbyl radical with the proviso that any alkenyl substitution be at least 3 carbon atoms removed from the phosphorus atom and at least one R is not H; and (c) an acid selected from the group consisting of (i) a fluorinated carboxcyclic acid of the formula R'COOH wherein R' represents a C 1 to C 10 hydrocarbyl radical having at least 1 fluorine (F) atom, (ii) a dicarboxcyclic acid of the formula (R") 2 --X--(COOH) 2 wherein R" independently represents H or a C 1 to C 20 hydrocarbyl or fluorinated hydrocarbyl radical and X is a tetravalent C atom or the tetra-substituted benzene radical C 6 H 2 ; (iii) 2-ketobutyric acid and (iv) glycine, such that the molar ratio of (b) to (a) is about 0.01-4.0 to 1 and the molar ratio of (c) to (a) is about 0.01-10.0 to 1 at a temperature of from about 0° C. to about 200° C.