Abstract: After acidification and separation of a concentrated aqueous solution of sodium sulfate, the water-containing organic phase that remains is first distilled to remove mainly water, then chilled to crystallize out the bulk of the dicarboxy acids, then esterified and distilled again to obtain monocarboxy acid esters in distillate fractions, after which the residue is further esterified to facilitate obtaining the remaining dicarboxy acids in usable form.

Abstract: The dimethyl ethers of succinic, glutaric and adipic acids show a great increase in their water miscibility when they are mixed with either 6-hydroxycaproic acid methyl ester, one or more of the glycol ethers, diglycol ethers and glycol ether acetates, or both 6-hydroxycaproic acid methyl ester and one or more of the glycol ethers, diglycol ethers and glycol ether acetates. These dimethyl esters are, accordingly, substituents for the glycol ether derivatives in water-miscible solvents for film-forming resins. They may provide up to 80% by weight of the non-water components of the solvent. They may be produced at the same time as the methyl ester of 6-hydroxycaproic acid in a single esterification step by esterifying a fraction of acids derived from the waste salt solutions of cyclohexanone manufacture, as described in a related application, Ser. No. 372,021, now U.S. Pat. No. 3,859,335.

Abstract: 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.degree. 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.

Abstract: Waste salt solution from cyclohexanone manufacture is acidulated in a neutralizer, after which the organic phase is separated and subjected to a counter-current extraction with a saturated aqueous solution of mostly monocarboxylic acids separated from a later stage of the process. The watery extract carries off sodium sulphate that would otherwise interfere with further refining and this extract is then returned to the neutralizing vessel where the waste salt solutions are being acidulated, thereby reducing the need for externally supplied water to keep sodium sulphate from precipitating in the neutralizer and also enabling the dissolved monocarboxylic acids to be recovered. The organic phase leaving the counter-current extractor then goes to a flash evaporator in a condition now free of sodium sulphate, so that the evaporator may continuously remove water and monocarboxylic acids, which are then condensed and separated, with the water phase going back to the extractor as previously mentioned.