Process for the separation of alpha-olefins by distillation of an effluent comprising ethylene and 1-butene

In a process for the separation of a mixture comprising:

• (a) ethylene, (b) a hydrocarbon cut principally comprising hydrocarbons containing 4 carbon atoms per molecule of which the major portion is 1-butene, (c) a hydrocarbon cut principally comprising hydrocarbons containing at least 6 carbon atoms per molecule of which the major portion consists of alpha-olefins containing at least 6 carbon atoms per molecule, the ethylene content of said mixture being in the range 30% to 70% by weight, said process comprising conducting the in separation in a distillation zone to obtain an overhead fraction and a bottoms fraction, the improvement comprising supplying said distillation zone with supplemental 1-butene in an amount in the range 1 to 40 times the quantity by weight of 1-butene present in said mixture and conducting the distillation so as to obtain an overhead fraction comprising the major portion of the ethylene present in said mixture and between 0% and 100% by weight of the total of both the 1-butene present in said mixture and in said supplemental 1-butene.