the drawing the process of the present invention is illustrated by means of a simplified schematic flow diagram in which such details as instrumentation heat exchange and heat recovery circuits separation facilities and similar hardware have been deleted as being non essential to an understanding of the techniques involved with reference now to the drawing a feed stream comprising butadiene and trace quantities of acetylene is introduced into the process via line 1 and is admixed with a polymer solvent comprising hexane carried via line 24 and the resulting admixture is carried via line 3 and is then admixed with a hydrogen rich gaseous stream introduced via line 2 this resulting admixture is carried via lines 4 and 5 valve 6 and lines 7 and 8 and introduced into selective hydrogenation zone 9 a stream containing a reduced concentration of acetylene compounds is removed from selective hydrogenation zone 9 via lines 10 and 11 valve 12 and lines 13 and 14 and is introduced into fractionation zone 15 a product stream comprising butadiene is removed from fractionation zone 15 via line 16 and recovered a polymer solvent comprising hexane and dissolved polymer compounds is removed from fractionation zone 15 via line 17 and a portion is carried via lines 22 23 and 24 and recycled to the inlet of selective hydrogenation zone 9 as hereinabove described another portion of the polymer solvent containing hexane and polymer compounds which is removed from fractionation zone 15 via line 17 is transported via line 18 and introduced into fractionation zone 19 a polymer solvent stream having a reduced concentration of polymer compounds.