Process for the conversion of ethylene into light alpha olefins with the use of additives based on quaternary ammonium salts

In a process for the conversion of ethylene into light alpha olefins wherein, in a reactor, under effective oligomerization conditions, the ethylene is brought into contact with a solution of a catalyst obtained by mixing a compound of zirconium with an organic compound selected from the class of acetals and ketals, esters, ketones, ethers, amines, nitriles, anhydrides, chlorides of acids, amides, aldehydes, thioethers, alkyl sulphides and disulphides, thiophenes, thioureas, and phosphines, and with a chloro or bromo compound of aluminium hydrocarbyl, the improvement comprising conducting the process in the presence of an amount of at least one quaternary ammonium salt effective to reduce the formation of polymer or adherence of polymer to walls of said reactor.