Catalyst for the production of light alpha olefins by oligomerization of ethylene

A catalyst for the conversion of ethylene into light alpha olefins, which comprises:

• a zirconium compound of the formula ZrX.sub.x Y.sub.y O.sub.z, in which X is a chlorine or bromine atom, Y is a radical selected from the group consisting of RO--, (R).sub.2 N-- and RCOO-- groups, in which R is a hydrocarbyl radical having 1 to 30 carbon atoms, x and y are 0 or an integer of 1 to 4, and z is 0 or 0.5, the sum x+y+2z being equal to 4,
• an organic acetal or ketal compound of formula ##STR2## in which R'.sub.1 and R'.sub.2 are independently a hydrogen atom or a hydrocarbyl radical having 1 to 30 carbon atoms and R.sub.1 and R.sub.2 are independently hydrocarbyl radicals having 1 to 30 carbon atoms, and
• an aluminum compound of the formula AlR".sub.n X.sub.3-n in which R" is a hydrocarbyl radical having 1 to 6 carbon atoms, X is a chlorine or bromine atom and n is a number of from 1 to 2,
• such that the molar ratio of the acetal or ketal compound to the zirconium compound is approximately 0.1:1 to 5:1 and the molar ratio of the aluminum compound to the zirconium compound is approximately 1:1 to 100:1.