Patent ID: 8513472

Claim:
A process for preparing 1,6-hexanediol from a carboxylic acid mixture containing adipic acid and 6-hydroxycaproic acid, wherein the carboxylic acid mixture is obtained as a by-product in oxidization of cyclohexane to cyclohexanone/cyclohexanol using oxygen or an oxygen-containing gas, the process comprises esterifying these acids with a lower alcohol, followed by hydrogenation, and the process is characterized by comprising the following steps of: a) separating a component having a boiling point lower than that of water and the alcohol used in the esterification from a mixture obtained by the hydrogenation in a first distillation step; b) separating an EV component having a boiling point higher than that of 1,6-hexanediol further in a second distillation step; c) separating an EV component having a boiling point lower than that of 1,6-hexanediol further in a third distillation step; and then d) obtaining 1,6-hexanediol in a fourth distillation step, in this order wherein 1,6-hexanediol has an ester value of 1 mg KOH/g or less.