Separation of acids and esters in the processing of waste salt solution of cyclohexanone manufacture

In a process for producing esters of monocarboxylic acids and also dicarboxylic acids or their esters from the waste aqueous solution of cyclohexanone manufacture which consists essentially of salts of monocarboxy and dicarboxy straight chain aliphatic acids and of hydroxycaproic acid, comprising the steps of acidifying such a waste salt solution with a strong acid to produce an aqueous phase and an organic phase and then separating a water-containing fraction from the resulting organic phase by distillation at temperatures up to 120.degree. C, followed by esterification of said water-containing fraction with a lower alcohol, the improvement whereby said distillation is accomplished in two distillation steps in a sequence of steps comprising the following:

• a first distillation step in which mainly water is distilled off;
• cooling the residue of said first distillation step to a temperature between +5.degree. C and -10.degree. C;
• separating crystals of solid dicarboxylic acids precipitated in the cooling step,
• and a second distillation step performed with fractionation at temperatures up to 120.degree. C using the liquid remaining after removal of the crystals, for separation of the more volatile components both from a hydroxyacid fraction recoverable as a separate fraction and from the dicarboxylic acids that remain in the liquid residue.