Aliphatic+ethanol separation via liquid–liquid extraction using low transition temperature mixtures as extracting agents

• Published in: Fluid phase equilibria 2015-05, Vol.394, p.71-82
• Main Authors: Rodriguez, Nerea R., Molina, Blanca Santacruz, Kroon, Maaike C.
• Format: Article
• Language: English
• Subjects: Aliphatic-alcohol; Chlorides; Coefficients; Computational fluid dynamics; Deep eutectic solvents; Liquid-liquid extraction; Low transition temperature mixtures; Phase equilibria; Selectivity; Separation; Transition temperature
• ISSN: 0378-3812; 1879-0224
• DOI: 10.1016/j.fluid.2015.03.017

Two different low transition temperature mixtures (LTTMs) were evaluated as potential extracting agents for the separation of the azeotropic mixtures {hexane+ethanol} and {heptane+ethanol} via liquid–liquid extraction. [Display omitted] •Low transition temperature mixtures (LTTMs) have been used as extracting agents.•The LLE data of the systems {aliphatic+ethanol+LTTM} have been measured.•The distribution coefficient and selectivity have been calculated and compared.•The experimental LLE data have satisfactorily been regressed using the NRTL model. In this work, two different low transition temperature mixtures (LTTMs), e.g., (i) glycolic acid–choline chloride molar ratio=(1:1) (GC(1:1)) and (ii) lactic acid–choline chloride molar ratio=(2:1) (LC(2:1)), were evaluated as potential extracting agents for the separation of the azeotropic mixtures {hexane+ethanol} and {heptane+ethanol}. Firstly, the liquid–liquid equilibrium (LLE) data of the ternary systems {hexane+ethanol+LTTM} and {heptane+ethanol+LTTM} were experimentally determined at T/K=298.15 and T/K=308.15. Secondly, the solute distribution coefficient and selectivity were calculated and analyzed. The influence of the temperature on the phase behavior and the performance of the LTTMs related to the chain length of the hydrocarbon were considered. A literature comparison with other extracting agents used for the separation of these mixtures was performed in order to evaluate the suitability of the studied LTTMs. Moreover, the recyclability of the extraction agent, which is of great importance in liquid–liquid extraction, was demonstrated. Finally, the experimental data were successfully fitted using the NRTL model. It was found that both LTTMs show a competitive performance compared to existing extracting agents. It was also established that both in the {hexane+ethanol} and {heptane+ethanol} separation, the LC(2:1) showed higher distribution coefficient than the GC(1:1), while the opposite trend was found for the selectivity values.