Azeotropic distillation process

Claim 1

IN A PROCESS FOR THE SEPARATION AND PURIFICATION OF THE COMPONENTS OF A MIXTURE OF A NORMALLY LIQUID ORGANIC CHEMICAL CONTAINING IMPURITIES, WHICH MIXTURE CANNOT BE SATISFACTORILY SEPARATED AND PURIFIED BY SIMPLY FRACTIONATION METHODS, THE IMPROVEMENT WHICH COMPRISES INTRODUCING SAID MIXTURE AND A SOLVENT FOR SAID CHEMICAL INTO A DISTILLATION COLUMN HAVING THE FOLLOWING ZONES THEREIN, SAID SOLVENT BEING SUBSTANTIALLY INERT WITH RESPECT TO THE COMPONENTS OF SAID MIXTURE: AN AZEOTROPIC DISTILLATION ZONE EXTENDING FROM THE FEED PLATE OF SAID COLUMN TO THE TOP THEREOF; AN EXTRACTIVE DISTILLATION ZONE EXTENDING FROM THE FEED PLATE DOWN TO A LOWER LEVEL OF SAID COLUMN BUT ABOVE THE REBOILER SECTION THEREOF; AND A SOLVENT REMOVAL ZONE, THE UPPER BOUNDARY OF WHICH IS ADJACENT THE LOWER LIMIT OF SAID EXTRACTIVE DISTILLATION ZONE AND THE LOWER BOUNDARY OF SAID SOLVENT REMOVAL ZONE BEING THE BASE OF SAID COLUMN, THE SOLVENT EMPLOYED BEING LOWER BOILING THAN THE CHEMICAL TO BE PURIFIED, AND FORMING A MINIMUM BOILING AZEOTROPE WITH SAID IMPURITIES, SAID SOLVENT ALSO BEING CAPABLE OF FORMING AN AZEOTROPE WITH SAID IMPURITIES LOWER BOILING THAN ANY OTHER DISTILLABLE FRACTION OF SAID MIXTURE HAVING AT LEAST ONE COMPONENT, THE CONCENTRATION OF THE SOLVENT IN SAID SOLVENT-IMPURITIES AZEOTROPE BEING SUFFICIENT TO CAUSE SAID IMPURITIES TO HAVE A HIGH VOLATILITY RELATIVE TO SAID CHEMICAL; ESTABLISHING, PRIOR TO THE WITHDRAWAL OF PURE CHEMICAL FROM THE LOWER PORTION OF SAID SOLVENT REMOVAL ZONE, AND MAINTAINING FROM PLATE TO PLATE A SUBSTANTIALLY CONSTANT CONCENTRATION OF LIQUID SOLVENT ON A MAJORITY OF THE PLATES IN SAID EXTRACTIVE DISTILLATION ZONE, SAID