Isoprene purification process

Claim 1

AN IMPROVED METHOD FOR THE SEPARATION OF ISOPRENE OF HIGH PURITY FROM A C5 HYDROCARBON FRACTION CONTAINING C5 MONOOLEFINS, C5 DIOLEFINS INCLUDING CYCLEOPENTADIENE, DIMETHYL ACETYLENE AND C5 ACETYLENES WHICH COMPRISES INTRODUCING A MIXTURE OF SAID COMPONENTS DIRECTLY TO MEANS FOR EFFECTING A STRAIGHT DISTILLATION, SUBJECTING SAID MIXTURE TO A STRAIGHT DISTILLATION TO SEPARATE A DISTILLATE FRACTION CONTINUING ISOPROPYL ACETYLENE, DIMETHYL ACETYLENE, PENTADIENE 1-4, VALYLENE AND A MINOR PROPORTION OF THE ISOPRENE FROM THE FEED AND A SECOND FRACTION CONTAINING C5 MONOOLEFINS, THE MAJOR PROPORTION OF THE ISOPRENE FROM THE FEED AND HIGHER BOILING COMPOUNDS, SUBJECTING SAID SECOND FRACTION TO EXTRACTIVE DISTILLATION IN THE PRESENCE OF A VOLATILITY MODIFYING SOLVENT TO SEPARATE A DISTILLATE FRACTION CONTAINING THE C5 MONOOLEFINS AND A SECOND FRACTION CONTAINING C5 DIOLEFINS AND HIGHER BOILING C5 ACETYLENES AND SUBJECTING THE LATTER TO A SECOND EXTRACTIVE DISTILLATION IN THE PRESENCE OF A VOLATILITY MODIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF ACETONE AND ACETONITRILE TO SEPARTE HIGH PURITY ISOPRENE AS THE DISTILLATE FRACTION AND A SECOND FRACTION CONTAINING VALYLENE, CYCLOPENTADIENE, PROPYLACETYLENE, CIS- AND TRANS-PIPERYLENE (PENTADIENE 1-3) AND ALLYLACETYLENE.