Ternary liquid–liquid equilibria for mixtures of an ionic liquid + n-hexane + an organic compound involved in the kinetic resolution of rac-1-phenyl ethanol (rac-1-phenyl ethanol, vinyl propionate, rac-1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure

doi:10.1016/j.fluid.2007.10.011

Fluid Phase Equilibria

Volume 263, Issue 2, 15 February 2008, Pages 190-198

https://doi.org/10.1016/j.fluid.2007.10.011 Get rights and content

Abstract

The liquid–liquid equilibrium of 16 ternary systems containing an ionic liquid + n-hexane + an organic compound involved in the racemic resolution of rac-1-phenylethanol (rac-1-phenylethanol, vinyl propionate, 1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure have been measured. The ionic liquids used were (i) 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim⁺][PF₆⁻]; (ii) 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim⁺][BF₄⁻]; (iii) 1-ethyl-3-methylimidazolium tosilate, [emim⁺][TOS⁻] and (iv) 1-butyl-3-methyl imidazolium ethylenglykolmonomethylethersulfate, [bmim⁺][MDEGSO₄⁻]. The binodal curves and the tie line compositions of the conjugate solutions were obtained by means of refractive index (ionic liquid rich phase) and by gas cromatography (hexane rich phase) to determine their potential for selectively extracting organic compounds from an ionic liquid reaction mixture. The tie lines were correlated by using the NTRL equation, which provides good correlation of the experimental data.

Introduction

Room temperature ionic liquids (RTILs) are organic salts that are liquid close to room temperature. They normally consist of an organic cation, the most commonly used being dialkylimidazolium and tetraalkylammomiun salts, and a polyatomic inorganic anion (e.g. BF₄⁻, PF₆⁻). The most important advantage of RTILs is their non-detectable vapour pressure, which makes them environmentally benign solvents compared with volatile organic solvents (VOSs). They also show good chemical and thermal stability and can be used at high temperatures [1]. Additionally, the physical-chemical properties of ionic liquids, such as their hydrophobicity, density, viscosity, melting point, polarity and solvent properties, may be modified by altering the anion or the cation [2], [3]. Indeed, this feature is a key factor for realizing successful extraction process since appropriate combinations of the cationic and anionic parts of the solvent can be made.

In recent years, ionic liquids have been shown to be good solvents for use in many chemical [4] and biochemical [5] processes. However, the extraction of the compounds from the IL medium need to be further studied, since it often involved the use of the conventional extraction technique of destillation, which demands high energy consumption. The extraction which supercritical carbon dioxide has been shown to be a very promising alternative from an environmental point of view [6]. Recent research has demonstrated the possibility of carrying out integral green biocatalytic processes by combining these two different neoteric solvents, room temperature ionic liquids and supercritical carbon dioxide (scCO₂) [7]. In order to study the use of scCO₂ as solvent extraction of the substrates from the RTIL phase, n-hexane could be use as reference organic solvent because its solvent capability is comparable to that of scCO₂ in mild operating conditions.

The aim of this work was to evaluate the liquid–liquid equilibrium of 16 ternary systems containing an ionic liquid + n-hexane + an organic compound involved in the racemic resolution of rac-1-phenylethanol (rac-1-phenylethanol, vinyl propionate, 1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure, since there are no thermodynamic data available for these systems involving ionic liquids. At present, the amount of physico-chemical data available for ternary mixtures involving ionic liquids is insufficient to create a data base of knowledge relating to their applicability in separation processes. The almost limitless number of combinations of cations and anions that can be made to produce ionic liquids futhers complicate matters [8], [9]. It is this correlation of the different combinations of cations and anions with the separation potential of the ionic liquid for specific mixtures of components that is of great potential interest to researchers. Therefore, the binodal curves and the tie-line data for 16 ternary systems containing an ionic liquid + n-hexane + an organic compound involved in the racemic resolution of rac-1-phenylethanol (rac-1-phenylethanol, vinyl propionate, 1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure have been determined. The ionic liquids used were (i) 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim⁺][PF₆⁻]; (ii) 1-butyl-3–methylimidazolium tetrafluoroborate, [bmim⁺][BF₄⁻]; (iii) 1-ethyl-3-methylimidazolium tosylate,[emim⁺][TOS⁻] and (iv) 1-butyl-3-methyl imidazolium ethylenglykolmonomethylethersulfate, [bmim⁺][MDEGSO₄⁻] (Fig. 1).

From the characteristics of the binodal curves and the tie line data for the ternary systems, valuable insight into the potential extractive capability can be gained. Selectivity values (S) were also determined from tie line data to study the feasibility of the use of n-hexane for the extraction of the organic compounds from the IL medium. The NTRL equation was used to correlate the experimental tie line data. The UNIQUAC equation was not used for data correlation because it is not applicable to ionic mixtures [9].

Section snippets

Materials

The ionic liquids [bmim⁺][PF₆⁻], [bmim⁺][BF₄⁻], [emim⁺][TOS⁻] and [bmim⁺][MDEGSO₄⁻] were purchased from Solvent Innovation (purity >99%), and were used as received. The RTILs were dried under anhydrous phosphorous pentoxide in vacuo and were stored in a desiccator to prevent any absorption of moisture. The water content of the RTILs were determined using Karl-Fischer technique and were less than 150 ppm in all cases. All other chemicals were purchased from Sigma–Aldrich Chemicals Co., and were

Results and discussion

The liquid–liquid equilibria of sixteen ionic liquid systems were determined: [bmim⁺][PF₆⁻] + propionic acid + n-hexane; [bmim⁺][BF₄⁻] + propionic acid + n-hexane; [emim⁺][TOS⁻] + propionic acid + n-hexane; [bmim⁺][MDEGSO₄⁻] + propionic acid + n-hexane; [bmim⁺][PF₆⁻] + rac-1-phenyletanol + n-hexane; [bmim⁺][BF₄⁻] + rac-1-phenyletanol + n-hexane; [emim⁺][TOS⁻] + rac-1-phenyletanol + n-hexane; [bmim⁺][MDEGSO₄⁻] + rac-1-phenyl etanol + n-hexane; [bmim⁺][PF₆⁻] + vinyl propionate + n-hexane; [bmim⁺][BF₄⁻] + vinyl propionate + n-hexane;

Conclusions

Ternary liquid–liquid equilibrium data were collected for mixtures of a room temperature ionic liquids ([bmim⁺][PF₆⁻], ([bmim⁺][BF₄⁻], [emim⁺][TOS⁻] or [bmim⁺][MDEGSO₄⁻]) + n-hexane + an organic compound involved in the kinetic resolution of rac-1-phenylethanol (rac-1-phenylethanol, vinyl propionate, 1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure.

The selectivity values were highest for [bmim⁺][PF₆⁻], indicating that it would be a better choice as a solvent for the

Acknowledgements

This work was partially supported by the CICYT CTQ2005-09238/PPQ grant. F.J. Hernández and A.P. de los Ríos have fellowships from the University of Murcia and the Spanish Ministry of Education and Science, respectively.

References (18)

F. van Rantwijk et al.
Trends Biotechnol.
(2003)
S. Machmudah et al.
J. Supercrit. Fluids
(2007)
T.M. Letcher et al.
Fluid Phase Equilib.
(2004)
T.M. Letcher et al.
Fluid Phase Equilib.
(1992)
T.M. Letcher et al.
J. Chem. Thermodyn.
(2005)
R. Kato et al.
Fluid Phase Equilib.
(2004)
R.A. Sheldon
Chem. Commun.
(2001)
S. Dzyuba et al.
Angew. Chem. Int. Ed.
(2003)
J.M. Pringle et al.
New J. Chem.
(2003)

There are more references available in the full text version of this article.

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Ternary liquid–liquid equilibria for mixtures of an ionic liquid + n-hexane + an organic compound involved in the kinetic resolution of rac-1-phenyl ethanol (rac-1-phenyl ethanol, vinyl propionate, rac-1-phenylethyl propionate or propionic acid) at 298.2 K and atmospheric pressure

Abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusions

Acknowledgements

Trends Biotechnol.

J. Supercrit. Fluids

Fluid Phase Equilib.

Fluid Phase Equilib.

J. Chem. Thermodyn.

Fluid Phase Equilib.

Chem. Commun.

Angew. Chem. Int. Ed.

New J. Chem.