Distillation of c1-c6 hydrocarbon mixtures

Claim 1

IN THE FRACTIONATION OF A MIXTURE OF SATURATED AND UNSATURATED HYDROCARBONS CONTAINING DIOLEFINS AND HAVING FROM ONE TO SIX CARBON ATOMS IN THE MOLECULE, THE IMPROVEMENT WHICH COMPRISES FRACTIONATING THE MIXTURE IN AN INITIAL FRACTIONATION ZONE TO OBTAIN THEREFROM A VAPOROUS FRACTION HAVING ONE TO THREE CARBON ATOMS IN THE MOLECULE AND SUBSTANTIALLY COMPLETELY FREE OF DIOLEFINS, A SECOND VAPOROUS FRACTION CONTAINING DIOLEFINS AND HAVING FROM FOUR TO FIVE CARBON ATOMS IN THE MOLECULE AND A THIRD FRACTION CONTAINING SIX AND MORE CARBON ATOMS IN THE MOLECULE, SEPARATELY REMOVING SAID FRACTIONS FROM SAID ZONE, PASSING SAID FRACTION HAVING FROM ONE TO THREE CARBON ATOMS IN THE MOLECULE THROUGH A DEHYDRATION ZONE, AND THENCE THROUGH A SERIES OF FRACTIONATION ZONES FROM WHICH DILUTE ETHYLENE VAPOR IS RECOVERED OVERHEAD FROM THE FIRST ZONE, CONCENTRATED ETHYLENE VAPOR IS RECOVERED OVERHEAD FROM A SECOND ZONE, AND PROPYLENE VAPOR OVERHEAD FROM A THIRD ZONE, A LIQUID CONDENSATE FROM EACH OF THE FIRST AND SECOND ZONES BEING INTRODUCED INTO THE SECOND AND THIRD ZONES RESPECTIVELY UNDER CONDITIONS OF INCREASING TEMPERATURE AND DECREASING PRESSURE IN EACH SUCCEEDING ZONE, REMOVING A LIQUID CONDENSATE FROM SAID THIRD ZONE AND PASSING SAID CONDENSATE AND SAID SECOND VAPOROUS FRACTION FROM THE INITIAL FRACTIONATION ZONE TO A FOURTH FRACTIONATION ZONE IN SAID SERIES OF ZONES UNDER HIGHER TEMPERATURE AND LOWER PRESSURE THAN IN SAID PRECEDING ZONES OF THE SERIES, AND SEPARATELY REMOVING THEREFROM A VAPOROUS FRACTION AND A FRACTION PRIMARILY CONTAINING MORE THAN FOUR CARBON ATOMS TO THE MOLECULE.