Butadiene purification

Claim 1

THE PROCESS FOR THE REFINING OF HYDROCARBON STREAMS TO PRODUCE BUTADIENE-1,3 OF A CONCENTRATION OF AT LEAST 98% BUTADIENE-1,3 AND CONTAINING LESS THAN 0.05% VINYL ACETYLENE COMPRISING THE STEPS OF FRACTIONALLY DISTILLING THE HYDROCARBON STREAM IN A FIRST FRACTIONAL DISTILLATION COLUMN TO PRODUCE A C4 HYDROCARBON MIXTURE CONSISTING ESSENTIALLY OF ISOBUTYLENE, BUTENE-1, BUTADIENE-1,3, N-BUTANE, TRANS-2-BUTENE, CIS-2-BUTENE, AND VINYL ACETYLENE; SUBJECTING THE SAID C4 HYDROCARBON MIXTURE TO EXTRACTIVE DISTILLATION WHEREBY ESSENTIALLY ALL OF THE BUTADIENE-1,3 AND VINYL ACETYLENE AND SOME OF THE 2-BUTENES ARE ABSORBED IN THE SOLVENT TO PRODUCT AT FAT SOLVENT, AND WHEREBY THE REMAINING C4''S ARE REMOVED OVERHEAD; STRIPPING THE SAID FAT SOLVENT WHEREBY THE BUTADIENE-1,3, 2-BUTENES AND VINYL ACETYLENE ARE TAKEN OFF AS AN OVERHEAD; FEEDING SAID OVERHEAD TO A SECOND FRACTIONAL DISTILLATION COLUMN, WITHDRAWING AT A RATE LESS THAN ABOUT ONE-THIRD THE FEED RATE TO SAID SECOND DISTILLATION COLUMN A SIDE STREAM CONTAINING A CONCENTRATION OF VINYL ACETYLENE GREATER THAN 0.1% AND WHICH CONCENTRATION IS HIGHER THAN THE VINYL ACETYLENE CONTENT OF THE HYDROCARBON MIXTURE BEING FRACTIONALLY DISTILLED, CONTACTING SAID SIDE STREAM WITH A DILUTE SODIUM DISPERSION IN AN AMOUNT FROM ABOUT 0.1 TO ABOUT 0.9 MOL SODIUM PER MOL OF VINYL ACETYLENE AND CONTAINING FINELY DIVIDED SODIUM PARTICLES OF AN AVERAGE PARTICLE SIZE FROM ABOUT 1 TO ABOUT 50 MICRONS UNDER SUCH CONDITIONS THAT GREATER THAN 10% OF SAID VINYL ACETYLENE IN THE SIDE STREAM IS REMOVED FROM THE HYDROCARBON MIXTURE BEING FRACTIONALLY DISTILLED, AND RETURNING THE TREATED HYDROCARBON TO SAID SECOND FRACTIONAL DISTILLATION COLUMN, WHEREBY THE MAXIMUM CONCENTRATION OF VINYL ACETYLENE IN THE SECOND DISTILLATION COLUMN IN LESS THAN ABOUT 5%, TO PRODUCE OVERHEAD THE SAID 98% CONCENTRATION BUTADIENE-1,3 WHICH CONTAINS LESS THAN 0.05% VINYL ACETYLENE.