Removal of vinylacetylenes from alkadienes

Claim 1

A PROCESS OF REDUCING VINYLACETYLENE CONCENTRATION TO BELOW 100 PARTS PER MILLION IN A C4 RO C5 ALKADIENE DISTILLATION PRODUCT FROM A C4 OR C5 ALKADIENE FEED STREAM CONTAINING 20 TO 90% C4 OR C5 ALKADIENE, AN UNDESIRABLE PROPORTION OF CLOSELY BOILING VINYLACETYLENES AND THE REMAINDER BEING ESSENTIALLY CORRESPONDING C4 OR C5 ALKENES BY: (A) FRACTIONALLY DISTILLING THE ALKADIENE FEED STREAM IN A DISTILLATION ZONE AND SEPARATING A CONCENTRATE STREAM ENRICHED IN AND CONTAINING AT LEAST ABOUT 1% AND NO MORE THAN ABOUT 3.5% BY WEIGHT VINYLACETYLENES; (B) CATALYSTICALLY HYDROGENATING THE CONCENTRATE IN UPFLOW THROUGH A BED OF 0.5% TO 5% BY WEIGHT PALLADIUM-ON-ALUMINA CATALYST TO SELECTIVELY HYDROGENATE THE VINYLACETYLENES TO A CONCENTRATION OF LESS THAN 100 PARTS PER MILLION WHILE INCREASING THE CONCENTRATION OF THE ALKADIENE THEREIN; (C) RECYCLING THE HYDROGENATION EFFLUENT TO THE FFED STREAM TO THE DISTILLATION ZONE; AND (D) WITHDRAWING THE ALKADIENE CONTENT OF THE FEED STREAM AS AN ENRICHED ALKADIENE STREAM OF LESS THAN 100 PARTS PER MILLION VINYLACETYLENES FROM THE DISTILLATION ZONE.