Process for manufacturing dicyanobutene

Claim 1

A PROCESS FOR REMOVING FERROCYANIDE IRON FROM A LIQUID AQUEOUS COPPER-CONTAINING PHASE CONTAMINATED WITH FERROCYANIDE IRON PRODUCED IN THE MANUFACTURE OF 1,4-DICYANO-2-BUTENE BY REACTION BETWEEN DICHLOROBUTENE AND HYDROGEN CYANIDE IN A LIQUID AQUEOUS ACIDIC MEDIUM CONTAINING A DISSOLVED COPPER COMPOUND AS CATALYST AT A PH OF 4 TO 6.5 WHICH COMPRISES LOWERING THE PH OF THE SAID AQUEOUS PHASE TO A VALUE BETWEEN 1.5 TO 2, WHEREBY SLURRY OF COPPER-CONTAINING COMPOUND IS PRODUCED, SAID SLURRY CONTAINING SUBSTANTIALLY ALL OF THE FERROCYANIDE IRON IN THE REACTION SYSTEM, CONCENTRATING THE SAID SLURRY BY REMOVAL OF LIQUID COMPONENT THEREFROM, ADMIXING THE RESULTANT CONCENTRATED SLURRY WITH ONLY ENOUGH AQUEOUS SODIUM CYANIDE TO PRODUCE A PH OF 4.0 TO 4.5, WHEREBY CUPROUS COPPER GOES INTO SOLUTION AND PART OF THE FERROCYANIDE IRON REMAINS UNDISSOLVED, SEPARATING THE LIQUID PHASE FROM THE REMAINING SLURRY AND RECYCLING THE SAID SEPARATED LIQUID, CONSTITUTING AN AQUEOUS COPPER-CONTAINING SOLUTION, TO A REACTION VESSEL WHEREIN AN AQUEOUS ACIDIC CATALYST-CONTAINING PHASE IS EMPLOYED IN THE REACTION BETWEEN HYDROGEN CYANIDE AND DICHLOROBUTENE TO PRODUCE 1,4DICYANO-2-BUTENE.