Patent ID: 8471042

Claim:
A process for preparing 1,6-hexanediol and ε-caprolactone from a carboxylic acid mixture, the process comprising: a) hydrogenating, in a first hydrogenation, employing a catalyst, only any aldehyde or ketone present in the carboxylic acid mixture to a corresponding alcohol and degrading more than 50% of formic acid present in the carboxylic acid mixture, to obtain a first hydrogenation mixture, wherein the catalyst for the first hydrogenation comprises at least one metal selected from the group consisting of Ru, Re, Co, Ni, and Cu, and the hydrogenating is carried out at a temperature of from 50 to 200° C. and at a pressure of from 5 to 35 bar; b) dewatering the first hydrogenation mixture to obtain a dewatered hydrogenation mixture; c) reacting, in a first esterification, any mono- or dicarboxylic acid present in the dewatered hydrogenation mixture with a low molecular weight alcohol to obtain a first esterification mixture comprising carboxylic esters corresponding to the mono- and dicarboxylic acids; d) removing, in a first distillation, excess alcohol and low boilers from the first esterification mixture to obtain a bottom product; e) separating, in a second distillation, the bottom product into an ester fraction depleted of 1,4-cyclohexanediols and a fraction comprising at least one 1,4-cyclohexanediol; f) at least partly removing, in a third distillation, a stream comprising predominantly 6-hydroxycaproic ester from the ester fraction; g) hydrogenating, in a second hydrogenation, employing a catalyst, the ester fraction from the third distillation from which 6-hydroxycaproic ester was removed at least partly, and distilling a product of the second hydrogenation to obtain 1,6-hexanediol; and h) heating the stream comprising predominantly 6-hydroxycaproic ester to temperatures greater than 200° C. under reduced pressure, to cyclize 6-hydroxycaproic ester to caprolactone, and distilling the caprolactone to obtain pure ε-caprolactone wherein the carboxylic acid mixture comprises: adipic acid; 6-hydroxycaproic acid; 6-oxocaproic acid; 4-hydroxycyclohexanone; formic acid; and, based on a sum of adipic acid and hydroxycaproic acid, between 0.5 and 5% by weight of at least one 1,4-cyclohexanediol, wherein the carboxylic acid mixture is obtained as a by-product of catalytic oxidation of cyclohexane to cyclohexanone/cyclohexanol with oxygen by water extraction of a reaction mixture.