455522 Isolation of Carboxylic Acids from Dilute Aqueous Solutions – Intensifying Approach By Conversion in Emulsified Reactive Solvents
The intensification of conventional separation techniques by combining with chemical reaction provides high potential in overcoming these obstacles. Two approaches, reactive distillation for the isolation of carboxylic acids and chemical conversion of the target constituents in both phases of a liquid-liquid extraction process, may offer a feasible option. Reactive conversion of choice for isolation of carboxylic acids is the esterification with an aliphatic alcohol, whereby the market value of the carboxylic acids can be significantly increased and the significant change of physical properties favorably influences the separation process.
As the partition behavior of the reactants is supportive when using higher aliphatic alcohols (e.g. n‑butanol or 1-octanol), the use of these alcohols, either dissolved in corresponding esters or hydrocarbon based solvents has been investigated. Catalysis and elevated temperature are provided to increase the reaction rate of the esterification reaction. 4‑dodecylbenzenesulfonic acid (4DBSA), a strong anionic surfactant and highly active homogeneous catalyst, has been used in the experimental validation in order to highly increase the contact between the reactants and the catalyst by emulsification. After having finished the reaction the emulsion is separated from the aqueous phase by settling and split by coalescence. A continuous process has been designed by altering conversion, phase separation, emulsion splitting and isolation of the product. Exemplarily 80% separation efficiency was obtained for acetic acid separation from aqueous feed by esterification with octanol in the emulsified solvent phase in single stage isolation.
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