THE PREPARATION OF 1, 6-HEXANEDIOL AND CAPROLACTONE

A PROCESS FOR PREPARING 1, 6-HEXANEDIOL AND e-CAPROLACTONE FROM A CARBOXYLIC ACID MIXTURE WHICH COMPRISES ADIPIC ACID, 6-HYDROXYCAPROIC ACID AND SMALL AMOUNTS OF 1,4-CYCLOHEXANEDIOLS AND WHICH IS OBTAINED AS BYPRODUCT OF THE OXIDATION OF CYCLOHEXANE TO CYCLOHEXANONE/CYCLOHEXANOL WITH OXYGEN OR OXYGEN-CONTAINING GASES BY WATER EXTRACTION OF THE REACTION MIXTURE, BY ESTERIFICATION AND HYDROGENATION OF A PART STREAM TO GIVE HEXANEDIOL AND CYCLIZATION OF 6-HYDROXYCAPROIC ESTER TO CAPROLACTONE, WHEREIN A) THE MONO- AND DICARBOXYLIC ACIDS PRESENT IN THE AQUEOUS REACTION MIXTURE ARE REACTED WITH A LOW MOLECULAR WEIGHT ALCOHOL TO GIVE THE CORRESPONDING CARBOXYLIC ESTERS, B) THE RESULTING ESTERIFICATION MIXTURE IS SUBJECTED TO A FIRST DISTILLATION STAGE TO REMOVE EXCESS ALCOHOL, WATER AND LOW BOILERS, C) A SECOND DISTILLATION STAGE IS CARRIED OUT ON THE BOTTOM PRODUCT FOR FRACTIONATION INTO AN ESTER FRACTION WHICH IS ESSENTIALLY FREE OF 1,4-CYCLOHEXANEDIOLS AND INTO A FRACTION WHICH COMPRISES AT LEAST THE GREATER PART OF THE 1,4-CYCLOHEXANEDIOLS, D) A THIRD DISTILLATION STAGE IS CARRIED OUT TO REMOVE FROM THE ESTER FRACTION AT LEAST PARTLY A STREAM WHICH ESSENTIALLY-COMPRISES 6-HYDROXYCAPROIC ESTER, E) THE ESTER FRACTION FROM (D), FROM WHICH 6-HYDROXYCAPROIC ESTER HAS BEEN AT LEAST PARTLY REMOVED, IS CATALYTICALLY HYDROGENATED AND THE HYDROGENATION PRODUCT IS DISTILLED IN A CONVENTIONAL MANNER TO ISOLATE 1,6-HEXANEDIOL AND F) THE STREAM WHICH ESSENTIALLY COMPRISES 6-HYDROXYCAPROIC ESTER IS HEATED TO ABOVE 200°C UNDER REDUCED PRESSURE, RESULTING IN CYCLIZATION OF 6-HYDROXYCAPROIC ESTER TO CAPROLACTONE, AND THE CYCLIZATION PRODUCT IS DISTILLED TO ISOLATE PURE e-CAPROLACTONE.