Article pubs.acs.org/jced
Liquid−Liquid Equilibria of Ionic Liquids−Water−Acetic Acid Mixtures Silu Wang,† Jingyi Liu,† Robert Hembre,‡ Scott Barnicki,‡ Peter Goodrich,† Terri-Louise Hughes,†,§ David W. Rooney,† Chester Sink,‡ Johan Jacquemin,*,† and Christopher Hardacre*,†,§ †
The QUILL Research Centre, School of Chemistry and Chemical Engineering, Queen’s University, Stranmillis Road, Belfast BT9 5AG, United Kingdom ‡ Eastman Chemical Company, 100 N. Eastman Road, Kingsport, Tennessee 37662, United States § School of Chemical Engineering and Analytical Science, University of Manchester, The Mill, Sackville Street, Manchester M13 9PL United Kingdom S Supporting Information *
ABSTRACT: The liquid−liquid equilibria of ionic liquid-based systems with water and/or acetic acid have been studied at 293.15 K and atmospheric pressure. One hydrophilic ionic liquid and a series of hydrophobic ionic liquids were investigated in order to examine their effect on the separation of water and acetic acid mixtures. The ionic liquids studied were [P666,14]Cl, [P666,14][NTf2], [C4mmim][NTf2], [Cnmim][NTf2] (n = 2, 4, 6, 8, or 10), [C4mpyrr][NTf2], [N1114][NTf2], and [C2mim][EtSO4]. [C2mim][EtSO4] is totally miscible with water and acetic acid in all compositions. Comparing [P666,14]Cl with [P666,14][NTf2], the former showed higher extraction selectivities; however, due to the larger viscosity of [P666,14]Cl, the [NTf2]− based ionic liquids offer a better solvent choice for the liquid extraction processes. As expected, as the solubility of water decreases with increasing the chain length of ionic liquids, this in turn leads to [C10mim][NTf2] showing greater acetic efficiency than [C2mim][NTf2] for the separation of water and acetic acid. The experimental data obtained for ternary systems containing the [C4mmim][NTf2] demonstrated that the modification of the C(2) position on the imidazolium ring does not significantly affect the selectivity compared with [C4mim][NTf2]. Tetraalkyl ammonium and N-alkyl pyrrolidinium based ionic liquids were also studied with the [NTf2]− anion with the results for the system containing the [C4mpyrr][NTf2] demonstrating a higher selectivity for the separation of water and acetic acid than the other [NTf2]− based systems studied. All experimental data were then correlated using the UNIQUAC model within an accuracy close to 1.6%. Finally, the ionic liquids were also compared with standard molecular extraction solvent, for example, methyl tert-butyl ether and methyl isobutyl ketone. The organic solvents showed an advantage over the [Cnmim][NTf2]-based ionic liquids but only over a narrow composition range. In all ionic liquid systems, the selectivity remains high at low acetic acid concentration compared with that found in the organic solvents, which is important for practical operation and demonstrates the advantages of using an ionic liquid for the extraction.
1. INTRODUCTION
of molecular solvents has been examined, including methyl tertbutyl ether (denoted MTBE), butyl acetate, propyl acetate, ethyl heptanoate, toluene, and heavy alcohols such as 1undecanol, 2-ethyl-1-hexanol, and so forth.7−13 MTBE was reported to have a high extraction efficiency for acetic acid recovery from aqueous solution with the liquid−liquid equilibria (LLE) not significantly affected by temperature below 318.15 K.11 Butyl acetate has a low solubility in water and high solubility for acetic acid and therefore is a good extraction media for the removal of acetic acid from water.10 These solvents have also been reported as entrainers to increase
Ionic liquids (ILs) have been proposed as promising solvents for a sustainable chemistry due to their negligible vapor pressure, high thermal stability, and ability to control their physicochemical properties, which has seen them be extensively used within the fields of catalysis1,2 and energy storage.3 For these reasons, they have been studied and extensively used for a number of liquid−liquid separation processes, for example, in aromatic−alkane separations4 and bioalcohol separations from aqueous streams.5,6 The separation of acetic acid from aqueous solutions is an important industrial process. However, due to the high energy cost, large number of stages in the column, and high reflux ratio, distillation is not a viable option.7 Thus, liquid−liquid extraction has been employed for the separation. A wide range © 2017 American Chemical Society
Received: August 1, 2016 Accepted: December 22, 2016 Published: January 11, 2017 653
DOI: 10.1021/acs.jced.6b00692 J. Chem. Eng. Data 2017, 62, 653−664
Journal of Chemical & Engineering Data
Article
Table 1. Specification of Chemicals Used chemical water acetic acid MTBE MIBK [C2mim][EtSO4] [P666,14]Cl [P666,14][NTf2] [C2mim][NTf2] [C4mim][NTf2] [C4mmim][NTf2] [C6mim][NTf2] [C8mim][NTf2] [C10mim][NTf2] [C4mpyrr][NTf2] [N1114][NTf2]
supplier d
in house Riedel-de Haëne Lancastere Sigma-Aldriche Merckg Cytecg in houseg in houseg in houseg in houseg in houseg in houseg in houseg in houseg in houseg
CAS number 7732-18-5 64-19-7 1634-04-4 108-10-1 342573-75-5 258864-54-9 460092-03-9 174899-82-2 174899-83-3 350493-08-2 382150-50-7 178631-04-4 433337-23-6 223437-11-4 258273-75-5
M g·mol−1 18.02 60.05 88.15 100.16 236.29 519.31 764.00 391.31 419.36 433.39 447.42 475.47 503.53 422.41 396.37
nominal purity % >99.95 >99f >98f >99f >98f >98f >98h >98h >98h >98h >98h >98h >98h >98h >98h
water content ppma
halide content ppmb
Li content ppmc
