Extractive distillation of closeboiling alcohols having partial immiscibility with water

Claim 1

A PROCESS FOR SEPARATING A MIXTURE CONSISTING ESSENTIALLY OF AT LEAST ONE NORMAL C3 TO C4 ALKANOL (A) AND AT LEAST ONE BRANCHED C3 TO C5 ALKANOL (B), THE AQUEOUS BOILING POINTS OF THE NORMAL AND BRANCHED ALKANOLS DIFFERING BY LESS THAN 5* C. WHICH COMPRISES INTRODUCING A MIXTURE OF SAID NORMAL AND BRANCHED ALKANOLS TO A FRACTIONAL DISTILLATION ZONE AT AN INTERMEDIATE POINT THEREOF, INTRODUCING SUFFICIENT WATER TO THE FRACTIONAL DISTILLATION ZONE AT A POINT SUBSTANTIALLY ABOVE THE ALKANOL MIXTURE FEED POINT TO MAINTAIN AN INTERNAL LIQUID AQUEOUS REFLUX HAVING A WATER CONTENT IN THE RANGE OF 85 TO 99 MOL PERCENT BELOW THE POINT OF ADDITION OF THE WATER, APPLYING HEAT TO THE FRACTIONAL DISTILLATION ZONE WHEREBY VAPORS OF THE ALKANOLS TOGETHER WITH WATER VAPOR ASCEND THROUGH THE FRACTIONAL DISTILLATION ZONE IN COUNTERCURRENT CONTACT WITH THE INTERNAL AQUEOUS LIQUID REFLUX, REMOVING OVERHEAD FROM THE FRACTIONAL DISTILLATION ZONE A VAPOROUS MIXTURE COMPRISING ALKANOL (B) SUBSTANTIALLY FREE FROM ALKANOL (A), AND REMOVING FROM A BOTTOM PORTION OF THE FRACTIONAL DISTILLATION ZONE A WATER SOLUTION OF SUBSTANTIALLY PURE ALKANOL (A).