Method of refining crude acrylonitrile

Claim 1

A CONTINUOUS METHOD OF REFINING AQUEOUS SOLUTION OF CRUDE ACRYLONITRILE CONTAINING IMPURITIES INCLUDING CYANOBUTADIENE WHICH COMPRISES CONTINUOUSLY EXTRACTING THE ACRYLONITRILE FROM THE SOLUTION BY MEANS OF A HYDROCARBON SOLVENT SELECTED FROM THE GROUP CONSISTING OF ETHYL BENZENE AND XYLENE, DISTILLING THE WATER AS ACRYLONITRILE AZEOTROPE FROM THE SOLVENT EXTRACT ALONG WITH SOME IMPURITIES; REMOVING THE VOLATILE IMPURITIES FROM THE DISTILLATE SO PRODUCED BY DISTILLATION, SEPARATING THE WATERACRYLONTRILE AZEOTROPIC MIXTURE AFTER REMOVAL OF VOLATILE IMPURITIES, INTO TWO LAYERS AT 10* C. TO 30* C., RETURNING THE LOWER LAYER WHICH IS PREDOMINANTLY WATER CONTAINING SOME ACRYLONITRILE TO THE SYSTEM TO BE ADMIXED WITH AQUEOUS SOLUTION OF CRUDE ACRYLONITRILE, AND RETURNING THE UPPER LAYER WHICH IS PREDOMINANTLY ACRYLONITRILE CONTAINING SOME WATER TO THE SYSTEM TO BE ADMIXED WITH SUBSEQUENTLY PRODUCED SOLVENT EXTRACT CONTAINING WATER AND ACRYLONITRILE; PASSING THE SOLVENT EXTRACT AFTER REMOVAL OF WATER TO A STILL AND REMOVING THE ACRYLONITRILE THEREFROM AS DISTILLATE ALONG WITH SOME SOLVENT AND SOME IMPURITIES, REMOVING AT LEAST A PART OF ANY CYANOBUTADIENE PRESENT FROM THE SOLVENT WHICH HAS BEEN FREED OF ACRYLONITRILE AND RETURNING THE SOLVENT TO THE SYSTEM FOR FURTHER USE IN EXTRACTION; PASSING THE ACRYLONITRILE DISTILLATE CONTAINING SOME SOLVENT AND IMPURITIES TO A STILL AND REMOVING REFINED DRY ACRYLONITRILE FROM THE SOLVENT AND IMPURITIES AS DISTILLATE AT 78* C., PASSING THE STILL BOTTOMS TO A VACUUM STILL OPERATING AT LESS THAN 150 MILLIMETERS OF MERCURY PRESSURE, REMOVING THE SOLVENT AND ANY ACRYLONITRILE PRESENT AS DISTILLATE, AND RETURNING THESE TO THE SYSTEM TO BE ADMIXED WITH SUBSEQUENTLY PRODUCED SOLVENT EXTRACT CONTAINING CRUDE ACRYLONITRILE.