PROCESS FOR PREPARING 1,5-PENTANEDIOL AND/OR 1,6-HEXANEDIOL

An objective is to provide a process for preparing 1,5-pentanediol and/or 1,6-hexanediol comprising esterifying, with an alcohol such as methanol, ethanol, butanol or 1,6-hexanediol, a mixture of carboxylic acids such as glutaric acid, adipic acid and 6-hydroxycaproic acid which are a by-product in preparation of cyclohexanone by oxidation of cyclohexane with oxygen or an oxygen-containing gas; and hydrogenating the resulting esterified product in the presence of a copper-containing catalyst, which process is an industrially suitable process for preparing 1,5-pentanediol and/or 1,6-hexanediol in a high yield while controlling deterioration of the catalyst. The above objective is achieved by hydrogenating the esterified product with a catalyst obtained by prereducing a copper-containing catalyst in an alcohol having an acid value (AV) of 0.5 mg KOH/g or less or an ester having an acid value (AV) of 0.5 mg KOH/g or less.