Absorption and distillation process for separating crude unsaturated nitriles from acetonitrile with selective solvent recycle

Claim 1

IN THE PROCESS FOR SEPARATING ACETONITRILE FROM AN A-B MONOOLEFINCALLY UNSATURATED NITRILE IN SOLUTION, THE IMPROVEMENT COMPRISING: (A) ABSORBING A MIXTURE COMPRISING ACETONITRILE AND SAID UNSATURATED NITRILE IN A SOLVENT (B) FEEDING THE LIQUID OBTAINED FROM (A) INTO A STAGE IN THE UPPER HALF OF A MULTIPLICITY OF INTERCOMMUNICATIVE EXTRACTIVE DISTILLATION STAGES (C) CONDENSING VAPORS REMOVED OVERHEAD FROM SAID STAGES, REMOVING CRUDE UNSATURATED NITRILE FROM THE CONDENSED OVERHEAD VAPORS WITHDRAWN FROM THE UPPERMOST OF SAID EXTRACTIVE DISTILLATION STAGES (D) WITHDRAWING A LIQUID FROM THE LOWEST OF SAID EXTRACTIVE DISTILLATION STAGES AND INTRODUCING IT INTO A STAGE IN THE UPPER HALF OF A MULTIPLICITY OF INTERCOMMUNICATING COUNTERCURRENT CONTACTING STRIPPING STAGES (E) WITHDRAWING OVERHEAD VAPORS FROM THE UPPERMOST OF SAID COUNTERCURRENT STAGES, CONDENSING SAID VAPORS AND RECOVERING CRUDE ACETONITRILE FROM THE CONDENSED ACETONITRILE VAPORS (F) WITHDRAWING FROM THE LOWER SECTION OF SAID COUNTERCURRENT STAGES A FIRST LEAN SOLVENT STREAM AND RETURNING SAID STREAM TO (A) AND (G) WITHDRAWING FROM THE LOWEST OF SAID COUNTERCURRENT STAGES A SECOND SOLVENT STREAM, RECYCLING THE MAJOR PORTION OF SAID SECOND STREAM TO A STAGE IN THE UPPER HALF OF SAID EXTRACTIVE DISTILLATION STAGES AND DISPOSING OF THE REMAINDER.