(408c) Intensification of Carboxylic Acid Isolation Processes By Emulsification
The change of properties, a tool of process intensification, can be combined within existing processes and equipment. Esterification of low grade carboxylic acids for example does change physical properties significantly. For esterification of carboxylic acids (e.g. acetic acid or formic acid) high excess of water is a major obstacle. Superimposition of the chemical conversion with liquid-liquid extraction can be used to overcome this limitation. Enhancement of the reaction rate as well as mass transfer, may be attained by catalyst-induced emulsification. Surface active, acidic catalysts like sulfonic acids (e.g. 4-dodecylbenzenesulfonic acid) accord with these requirements.
As a test system 60 g L-1 acetic acid was chosen with n-octanol as reactant and n-undecane as diluent. 4-dodecylbenzenesulfonic acid was used as catalyst, due to its good performance in esterification catalysis and due to its emulsification properties. Experiments were performed in order to determine the influence of catalyst, reaction temperature and solvent composition on the reaction kinetics and separation efficiency. Experimental results for esterification of dilute acetic acid with n-octanol in the emulsion regime have shown the applicability of pseudo-homogeneous rate laws for modeling the reaction kinetics. This implies a quasi-homogeneous state as a result of emulsification. For implementation of this intensified process, a mixer-settler setup is suitable as it allows higher conversions and separation efficiencies through multi-stage operation. Phase separation can be achieved through centrifugation or electrical splitting.