Process for separation of monocarboxylic acids from a mixture of monocarboxylic, hydroxycarboxylic and dicarboxylic acids

摘要

In a process for producing esters of carboxylic acids from the waste salt solutions derived from the manufacture of cyclohexanone, the mixture of organic acids obtained by acidulation with a strong acid and separation of an inorganic salt solution is refined to separate the monocarboxylic acids from the hydroxycarboxylic and dicarboxylic acids by a three-stage distillation at a temperature lower than 120 DEG C. The first stage is performed at a moderate vacuum, the second stage at a higher vacuum and the third stage is a steam distillation stage at a moderate vacuum, with the steam requirements reduced by returning to the evaporator an aqueous phase that is readily separated from the distillate. The use of steam in this manner only in the third stage reduces the steam requirements to economic proportions. More than 99% of the monocarboxylic acids may be separated from the other carboxylic acids in this fashion.