Use of ionic liquids to separate diolefins

A process for separating one or more members selected from the group consisting of C4-8 diolefin hydrocarbons which are unsubstituted or substituted by up to three C1-4 alkyl radicals from a mixture comprising at least one of said diolefins and at least one other hydrocarbon selected from the group consisting of C1-18 paraffins and mono-olefins comprising contacting said mixture with a nitrogen containing ionic liquid having a melting temperature below 80° C. to preferentially take said one or more diolefins into said ionic liquid, separating said ionic liquid from said at least one other hydrocarbon and regenerating said ionic liquid and releasing said at least one diolefin.