Method of production of improved purity light alpha olefines by ogliomerisation of ethylene

A method for conversion of ethylene into improved purity light alpha olefines, comprising the steps of:

• contacting ethylene with an oligomerization catalyst obtained by mixture:
• of a zirconium compound with the formula ZrX.sub.x Y.sub.y O.sub.z in which X is an atom of chlorine or bromine, Y is a radical selected from the group consisting of RO.sup.- alkoxys, R.sub.2 N.sup.- aminos, and RCOO.sup.- carboxylates, where R is a hydrocarbyl radial having 1 to 30 carbon atoms, x and y can have whole values from 0 to 4 and z equals 0 or 0.5, the sum of x+y+2z being equal to 4,
• with an organic compound with the formula (R.sub.1 ')(R.sub.2 ')C(OR.sub.1)(OR.sub.2) in which R.sub.1 ' and R.sub.2 ' are constituted by one atom of hydrogen or a hydrocarbyl radical having 1 to 30 carbon atoms, and R.sub.1 and R.sub.2 are hydrocarbon radicals having 1 to 30 carbon atoms,
• and with an aluminum compound with the formula AIR".sub.n X.sub.3-n in which R" is a hydrocarbyl radical having 1 to 6 carbon atoms, X is an atom of chlorine or bromine, and n is a number between 1 and 2,
• conducting an oligomerization of said ethylene to produce a raw oligomerization effluent,
• introducing into the raw oligomerization effluent a deactivating agent consisting essentially of at least one amine and
• subjecting the resultant deactivated oligomerization effluent to vaporization so that unreacted ethylene and alpha olefin oligomers thereof are collected in the vaporized fraction.