Separation of unsaturated hydrocarbons from a fluid mixture

Process for the separation of an unsaturated hydrocarbon from a fluid mixture with at least one other hydrocarbon wherein the unsaturated hydrocarbon is separated from the fluid mixture in a gas/liquid membrane contactor by passing the fluid mixture over a selective gas separation membrane, said selective membrane at least consisting of (a) a porous support material and (b) a non-porous active layer comprising at least one material, preferably present at the side of the membrane where the absorbent liquid is passed, wherein the active layer at least consists of a material with a high affinity for the complexing agent, such as a cation-exchange material comprising anionic functionalities or a material partitioning preferentially the complexing agent.