Process for the oligomerization of butenes

Oligomerization of butenes with a transition metal catalyst using a hydrocarbon feed wholly or partly of a stream (1) containing predominantly butene and obtained by separation from a stream (2) with a low butenes content is such that stream (1) is obtained by extractive distillation and distillative separation from a stream (2) containing saturated and unsaturated 4C hydrocarbons, followed by washing and drying. Oligomerization of butenes with a transition metal catalyst using a hydrocarbon feed wholly or partly of a stream (1) containing predominantly butene and obtained by separation from a stream (2) with a low butenes content is such that stream (1) is obtained by (A) extractive distillation of a stream (2) containing saturated and unsaturated 4C hydrocarbons using a polar extractant to give a saturated hydrocarbon-enriched top fraction (3) and a sump fraction (4) enriched in unsaturated hydrocarbons and containing the extractant; (B) distillative separation of sump fraction (4) to give a top fraction (5) containing butene as unsaturated hydrocarbon and a sump fraction (6) containing the extractant; (C) washing at least a part of fraction (5) with water or an aqueous solution; and (D) drying fraction (5) to give an anhydrous butene-containing hydrocarbon stream.