Experimental Determination and Correlation of LiquidâLiquid

Article pubs.acs.org/jced

Experimental Determination and Correlation of Liquid−Liquid Equilibria Data for a System of Water + Ethanol + 1‑Butyl-3methylimidazolium Hexafluorophosphate at Different Temperatures Amparo Cháfer,* Javier de la Torre, Juan B. Montón, and Estela Lladosa Departamento de Ingeniería Química, Escuela Técnica Superior de Ingeniería, Universitat de València, 46100 Burjassot, Valencia, Spain ABSTRACT: Over the past few years, interest has increased regarding the application of ionic liquids (ILs) as extraction solvents for separating azeotropic mixtures. Following this trend, this work presents the experimental data of liquid−liquid equilibria (LLE) of the system envolving water, ethanol, and 1-butyl-3methylimidazolium hexafluorophosphate ([bmim][PF6]) at different temperatures. The LLE data of the system was measured between 283.2 and 323.2 K to determine the temperature influence on the system. In the literature, reports of systems involving ILs that present type II behavior are scarce compared with those that present type I behavior; the system presented here also displays two immiscibility zones in the ternary system. The universal quasichemical (UNIQUAC) and nonrandom two-liquid (NRTL) models were applied to correlate the ternary system. Both of the models obtained fit the equilibrium compositions and showed type II behavior; nevertheless, UNIQUAC presented a better result. Finally, the solvent ability of the IL for the purpose of separating the mixture formed by ethanol and water was evaluated and compared with other ionic liquids studied in the literature.

1. INTRODUCTION Bioethanol is a product obtained via the fermentation of different types of carbohydrates, which can proceed from a large variety of raw materials. On the other hand, its use as another choice to traditional fuels in many different applications is increasing, as it is considered more environmentally friendly due to its cleaner combustion and reduced atmospheric CO2 emissions.1,2 This issue is of increasing concern to society, and hence this type of fuel alternative is important, not only for the reduction of CO2 emissions but also because it is obtained from byproducts. The fermentation stage does not incur significant cost in the production of bioethanol; however, the subsequent bioprocess to purify the ethanol from fermentation broths does. This is due to the high-energy consumption of the distillation technique used in most cases. Also, for the concentration of ethanol in broth, around 5−15% (mass), there is no technical problem for the separation;3 however, the energy cost necessary to separate the ethanol from the aqueous mixture by any distillation technique typically consumes 10% of the energy capacity of the ethanol produced,2,4 and this value rises exponentially for ethanol contents lower than 10 wt %. On the other hand, alternative distillation processes are only effective until the concentration of the azeotrope ethanol + water is reached. If one wants to obtain a higher purity of ethanol, other complementary alternatives are required, which increases the economic cost of the process.3,4 Liquid−liquid extraction is another alternative used that requires less energy.3−5 This alternative could reduce the © 2017 American Chemical Society

consumption of energy during the extraction process of an ethanol−water mixture by around 40%, if it is compared with a traditional distillation.6 Our research group previously made a study of separating alcohol + water mixtures using liquid−liquid extraction with conventional solvents.5,7,8 The study of ionic liquids (ILs) as possible sustainable alternatives to conventional solvents has increased in the past few years, due to their capacity to break the azeotrope9 and their null volatility at room temperature, which implies that the recycling process could be easy. Some reports exist regarding systems involving alcohols (such as 1-butanol, 1-propanol, or 2-propanol), water, and ILs as solvents;10−15 however, few articles address ethanol + water azeotrope separation using ILs as solvents in the LLE processes. Among other studies, Neves et al.1 and Chowdhury et al.16 used phosphonium-based ILs. Chapeaux et al.17 and Chafer et al.18 used imidazolium-based ILs, and finally, Swalonki et al.19 and Najdanovic-Visak et al.20 used hexafluorophosphate-based ILs. Also, the majority of these reported data are binodal or cloud point data, which do not provide information about the feasibility of extraction. In these cases, to implement and design LLE methods to obtain alcohols from water, it is necessary to consider the tie lines of the ternary system, in order to model the phase behavior. This is the case for the ethanol + water + 1butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) ternary system, where the data provided in the literature Received: September 23, 2016 Accepted: December 28, 2016 Published: January 9, 2017 773

DOI: 10.1021/acs.jced.6b00829 J. Chem. Eng. Data 2017, 62, 773−779

Journal of Chemical & Engineering Data

Article

was maintained within ±0.1 K using a thermostated bath, which was integrated with the equipment. The uncertainties associated with refractive index and density measurements were ±0.0002 and ±0.01 kg·m−3, respectively. The values of density and refractive index are given in Table 2 and compared with other results from the literature. 2.2. Apparatus and Procedure. The equipment and experimental method developed for obtaining LLE data is presented in previous work.30 The experimental tie lines were determined by weighing mixtures with a bulk composition in the region of immiscibility. These samples were introduced in test tubes, taking the precaution of fill them almost completely. The time necessary to reach the equilibrium was established in preliminary experiments. The temperature was maintained using a thermostated bath which incorporates a stirring system (Unitronic Orbital from Selecta). Finally, the samples were intensely stirred for at least 10 h and then left to stand for at least 12 h at constant temperature. The uncertainty of the temperature measurements was ±0.1 K (obtained using an Amarell thermometer, supplied by VWR with a calibration certificate). A sample was taken from both phases when equilibrium was attained. Then, the samples were analyzed using the gravimetric method and gas chromatography, following the methodology described in a previous work.18 2.3. Analysis. A piece of equipment developed by our research group31 was used to determine the composition of the sampled liquid phases, following the steps described in a previous study.18 In order to separate the volatile reagents, the sample is distilled. The vapor is condensed (it does not contain IL) and analyzed by chromatography to determine the relative composition of ethanol and water. The IL is not introduced to the chromatograph, and so the equipment is protected. The relative composition of the volatile compounds is determined using a Series chromatograph equipped with a TCD detector, an integrator (HP3395), and a 2 m × 1/8 in. column packed with Porapack Q-S 80/100. The temperatures of the column, injector, and detector were 443, 453, and 473 K, respectively. Under the conditions described was attained a very good peak separation. A calibration was carried out to convert the peak area ratio to the mass composition of the samples. Methanol was added to sample and calibration vials in order to homogenize the samples. The uncertainty in the mole fraction was usually less than 0.001, taking into account that for each liquid composition were made at least two analyses. Finally, after eliminating the volatile components from a known mass of sample by evaporation to dryness, it is possible establish gravimetrically the total amount of volatile compounds and IL in the sample. Like this, the compositions of all components of system, in both phases, were determined experimentally. Several authors reported the formation of HF in mixtures of water + [bmim][PF6] at elevated temperatures.20,32,33 Freire et

are cloud points. Moreover, given the limited accuracy of this experimental method, there is disagreement within the published experimental data. Finally, this is one of the scarce type II systems involving ILs that are reported in the literature. The other problem is the modeling of type II systems involving ILs. To our knowledge, there are no successful reports of this in the literature. Some authors have tried to use NRTL, e-NRTL, and UNIQUAC as predictive models but without success,19,20 as the predictions predict type I behavior for the ethanol + water + [bmim][PF6] ternary system. Nevertheless, some authors successfully predict the LLE of type I systems involving ILs.21−23 In light of this, this work tries to contribute a solution to these handicaps by presenting the experimental tie lines for the ternary mixture [bmim][PF6] + ethanol + water at different temperatures and their correlation using activity coefficient models. Moreover, a study of temperature influence on the type II system behavior is also included, as well as modeling of the phase behavior, which is important in the design of the extraction processes and difficult in type II systems involving ILs. Finally, LLE data were successfully correlated using the activity coefficient models UNIQUAC24 and NRTL25 and are capable of reproducing the type II behavior of the system. Finally, the solvent capability of the IL was studied through the selectivity and distribution coefficient determination and was compared with other ILs studied in the literature.

2. EXPERIMENTAL SECTION 2.1. Chemicals. Bidistilled water and ethanol (w = 0.998, assay GC) were provided from Fluka. [Bmim][PF6] (w (mass fraction) > 0.99) was supplied by Iolitec. The purity of ethanol and water was checked using a chromatograph. A description of chemicals is given in Table 1. Appropriate precautions were Table 1. Description of Reagents chemical name [bmim] [PF6] water ethanol methanol

purity (mass fraction)

analysis method

Iolitec

>0.990

gravimetric

none

Fluka Fluka Across Organics

0.998 0.998 0.999

GC GC GC

degas dry and degas dry and degas

supplier

purification method

taken during the handling of chemicals in order to avoid hydration. Before measurements, the liquids were degassed and dried over molecular sieves. The densities of the chemicals were obtained at 298.15 K using an densimeter (Anton Paar DMA 58), and the refractive index was measured at 298.15 K (Abbe refractometer Atago 3T). The water content, measured using a Karl Fischer volumetric automatic titrator (Metrohm, 701 KF Titrino), was low in all reagents (w < 0.0005). The temperature

Table 2. Density ρ, Refractive Index nD, and UNIQUAC Structural Parameters of Pure Components at p = 0.101 MPa ρa (kg m−3) (298.15 K) component water ethanol [bmim][PF6]

exptl. 997.06 786.47 1367.40

nDa (298.15 K)

lit.

exptl. b

997.05 785.01b 1363.70c

1.3325 1.3594 1.4095

UNIQUAC parameters r

lit. b

1.3325 1.3594b 1.4084d

q c

0.9200 2.5755c 11.03e

1.3997b 2.5880b 6.96d

Standard uncertainties u are u(nD) = 0.0002, u(ρ) = 1 kg·m−3, u(P) = 0.1 KPa, u(T) = 0.1 K. bTaken from TRC tables.26 cDECHEMA.27 dTariq et al.28 eBanerjee et al.29 a

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al.33 evaluated the thermal and chemical decomposition of hexafluorophosphate- and imidazolium-based ILs in aqueous solution. Their study concluded that it is possible to use aqueous solutions of hexafluorophosphate-based ILs at moderate temperatures, like that used in this work for ELL measurements (283−323 K). On the other hand, they established the conditions of stability of [bmim][PF6] in aqueous mixtures. These conditions are taken into account in the gravimetric measurements of samples.

Table 4. Experimental Tie Lines Determined at 101.30 kPa of the System Water (1) + Ethanol (2) + [bmim][PF6] (3)a, Distribution Coefficient of Ethanol (K2), and Selectivity (S) at 303.2 K [bmim][PF6] rich phase

3. RESULTS AND DISCUSSION 3.1. Experimental Data. The measurements of LLE data for a water (1) + ethanol (2) + [bmim][PF6] (3) system were carried out at 283.2, 303.2, and 323.2 K at atmospheric pressure. The experimental data for this system are shown in Tables 3 to 5 and Figures 1 to 3. In these tables and figures, all concentrations are presented in mole fractions. Table 3. Experimental Tie Lines Determined at 101.30 kPa of the System Water (1) + Ethanol (2) + [bmim][PF6] (3)a, Distribution Coefficient of Ethanol (K2), and Selectivity (S) at 283.2 K [bmim][PF6] rich phase

water rich phase

x1

x2

x1

x2

K2

S

0.297 0.315 0.318 0.347 0.356 0.386 0.417 0.428 0.442 0.491 0.076 0.102 0.127 0.000

0.000 0.030 0.073 0.125 0.162 0.199 0.215 0.249 0.283 0.298 0.581 0.605 0.599 0.582

0.999 0.977 0.946 0.907 0.877 0.845 0.810 0.780 0.725 0.689 0.078 0.105 0.133 0.000

0.000 0.022 0.052 0.091 0.119 0.150 0.181 0.207 0.254 0.276 0.903 0.871 0.834 0.990

1.389 1.393 1.380 1.361 1.329 1.189 1.203 1.115 1.080 0.643 0.694 0.719 0.588

4.306 4.148 3.604 3.352 2.905 2.310 2.192 1.827 1.516 0.665 0.714 0.752 -

a Standard uncertainties u are u(T) = 0.1 K, u(x) = 0.001, u(P) = 0.1 KPa.

water rich phase

x1

x2

x1

x2

K2

S

0.205 0.221 0.221 0.218 0.229 0.237 0.248 0.258 0.269 0.273 0.278 0.278 0.286 0.288 0.295 0.288 0.280 0.274 0.254 0.233 0.193 0.164 0.133 0.078 0.059 0.000

0.000 0.019 0.043 0.087 0.122 0.156 0.180 0.197 0.220 0.234 0.253 0.260 0.268 0.282 0.298 0.326 0.349 0.364 0.397 0.413 0.426 0.432 0.433 0.434 0.430 0.434

0.999 0.974 0.943 0.905 0.871 0.838 0.807 0.774 0.732 0.707 0.674 0.651 0.625 0.603 0.561 0.519 0.488 0.454 0.395 0.352 0.279 0.241 0.193 0.111 0.081 0.000

0.000 0.025 0.056 0.094 0.127 0.159 0.190 0.222 0.261 0.285 0.315 0.336 0.360 0.381 0.419 0.458 0.485 0.517 0.575 0.621 0.700 0.743 0.795 0.881 0.912 0.996

0.744 0.770 0.921 0.959 0.979 0.948 0.890 0.842 0.821 0.802 0.774 0.744 0.742 0.711 0.711 0.719 0.703 0.690 0.665 0.608 0.582 0.545 0.492 0.472 0.436

3.287 3.286 3.824 3.656 3.459 3.091 2.670 2.290 2.129 1.947 1.816 1.629 1.553 1.354 1.282 1.253 1.167 1.070 1.003 0.882 0.857 0.787 0.705 0.657 -

Table 5. Experimental Tie Lines Determined at 101.30 kPa of the System Water (1) + Ethanol (2) + [bmim][PF6] (3)a, Distribution Coefficient of Ethanol (K2), and Selectivity (S) at 323.2 K [bmim][PF6] rich phase

water rich phase

x1

x2

x1

x2

K2

S

0.403 0.417 0.447 0.477 0.499 0.534 0.561 0.000

0.000 0.044 0.092 0.151 0.178 0.191 0.205 0.765

0.998 0.974 0.951 0.913 0.884 0.832 0.803 0.000

0.000 0.023 0.046 0.082 0.108 0.153 0.172 0.958

1.942 2.017 1.845 1.643 1.251 1.194 0.798

4.540 4.287 3.530 2.913 1.948 1.708 -

a

Standard uncertainties u are u(T) = 0.1 K, u(x) = 0.001, u(P) = 0.1 KPa.

completely miscible. On the other hand, the temperature has a large influence on the system, as is shown in Figure 4. In fact, at 283.2 K the ternary system exhibits a large two-phase region, with an accused flexion in the IL phase region at medium ethanol concentrations. Nevertheless, at 303.2 K there are two independent immiscibility gaps. Finally, at 323.2 K, the immiscibility gap corresponding to high IL concentrations disappears, meaning that any water addition creates the miscible ternary mixture. Thus, there is only an immiscibility gap at 323.2 K. There is only an immiscibility gap (the ternary system becomes type I) at 323.2 K, and the slope of the tie lines could be adequate for extraction (the ethanol has greater affinity to the IL than with the water); however, in the literature there are other ILs that show better results for the separation of an ethanol + water system.16,18,19 Moreover, the recovery of IL by distillation must be performed at low pressure in order to reduce the temperature and avoid the formation of HF. Thus; the use of [bmim][PF6] for use in the extraction process could be recommended, if appropriate precautions are taken.

a Standard uncertainties u are u(T) = 0.1 K, u(x) = 0.001, u(P) = 0.1 KPa.

As can be deduced from observation of Figures 1 to 3, the liquid−liquid phase diagrams for this system are very singular. To our knowledge, this system is the only type II system reported in the literature for water + ethanol + IL, where two binary subsystems have partial miscibility and the binary subsystem is miscible.34 Therefore, the [bmim][PF6] + water and [bmim][PF6] + ethanol binary systems show an immiscibility gap, and the binary ethanol + water are 775



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Figure 1. Liquid−liquid equilibria of the water (1) + ethanol (2) + [bmim][PF6] (3) system at T = 283.2 K. Experimental data (●) [bmim][PF6] rich-phase, (▲) aqueous phase, () experimental tie lines. Calculated data using the UNIQUAC model: (○) [bmim][PF6] rich-phase, (△) aqueous phase, (...) tie lines. (■) Literature data of cloud point from Najdanovic-Visak et al.14


work, the authors did not succeeded in predicting the type II behavior of the system using these models. Thus, it is necessary obtain experimental data of tie lines to modelate the system and calculate reliable parameters for the models. Toward this aim, the experimental tie lines for the ternary systems were correlated at three different temperatures. The Chemcad37 regression tool was used to fit parameters to the experimental data. To obtain liquid-phase activity coefficients, the excess Gibbs energy models UNIQUAC and NRTL were used. Some data of [bmim][PF6] was introduced, since the database of Chemcad does not provide any data of the IL. The minimum required data needed for each component to carry out the liquid−liquid calculations are the UNIQUAC area (q) and volume (r) parameters (Table 2), the molecular weight, and the vapor pressure. Taking into account that ILs have negligible vapor pressure, proper fictional constants based Antoine’s equation are fixed for the IL. To correlate the binary UNIQUAC interaction parameters, the structural parameters (r and q) recommended by DECHEMA27 and Banerjee et al.,29 were applied for the pure components and are shown in Table 2. The nonrandomness parameter (αij) used in the NRTL model (given in Table 6) was fixed to 0.2 or 0.3 and maintained in all cases, as these values are recommended in the literature for such systems.25,34 Finally, the α parameter of the NRTL model was maintained constant at 0.3, because the correlations using an α parameter equal to 0.2 showed no further improvement in the results. The correlation of experimental data was carried out separately at each temperature, so the temperature dependency of the parameters was not considered. The binary interaction parameters for both models was obtained by minimizing the differences between the calculated and the experimental equilibrium mole fractions for all the experimental tie lines and for each of the components. Like this, it were determined for a ternary system six effective binary interaction parameters, since there are two effective binary interaction parameters for each binary subsystem. In this work, the objective function (OF) used is


Figures 1 to 3 show some cloud point data of a system described in the literature.20 As some authors have reported,20 the discrepancies between data within the literature regarding the binary systems involved in the water (1) + ethanol (2) + [bmim][PF6] (3) system could perhaps be due to the fact that equilibrium is not reached under the fixed experimental conditions. On the other hand, there are also discrepancies between the cloud point data that is determined experimentally at similar temperatures by different authors, as noted by Najdanovic-Visak et al.20 This is because in such complex systems it is difficult to know within which immiscibility zone it is working when this experimental method is applied. 3.2. Data Correlation. Simoni et al.35 tried to predict the behavior of a system using different models of local composition: NRTL,25 e-NRTL,36 and UNIQUAC.24 In this 776



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Figure 4. Influence of temperature on the liquid−liquid equilibrium of the water (1) + ethanol (2) + [bmim][PF6] (3). Experimental data: (●), at 283.2 K; (▲), at 303.2 K; (▼), at 323.2 K.

Table 6. Binary Interaction Parameters of UNIQUAC and NRTL Models for Water (1) + Ethanol (2) + [bmim][PF6] (3) UNIQUAC parameters

NRTL parameters

T (K)

i−j

Aij (J mol−1)

Aji (J mol−1)

rmsd (%)

αij

Aij (J mol−1)

Aji (J mol−1)

rmsd (%)

283.2

1−2 1−3 2−3 1−2 1−3 2−3 1−2 1−3 2−3

−1090.60 −5.39 −2205.38 216.63 255.58 −2578.99 964.81 465.98 −488.80

3724.86 5444.53 4129.84 1339.09 4927.16 5080.99 −2187.08 4381.29 −1588.06

0.261

0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3

4788.38 8314.57 9505.66 8176.17 10602.88 12471.05 2520.01 11466.47 7885.13

232.98 2079.48 −322.82 −1837.51 1426.55 −2136.16 −3256.25 540.77 −6750.05

0.640

303.2

323.2

M

OF =

2

0.273

0.352

3

(1)

where x̂ is the calculated mole fraction, x indicates the experimental mole fraction, M is the number of tie lines, and subscripts i, j, and k denote the component, phase, and tie line, respectively. The binary interaction parameters calculated following these steps are given in Table 6. In this table, the root-mean-square deviation (rmsd) of the phase compositions are also included. These values are calculated according the following equation: ⎛ M 2 3 (x − x ̂ )2 ⎞1/2 ijk ijk ⎟ rmsd(%) = 100⎜⎜ ∑ ∑ ∑ ⎟ 6M ⎠ ⎝ k=1 j=1 i=1

0.481

parameters obtained for both models can successfully reproduce the type II behavior of the system, as can be observed in Figures 1 to 3 for the UNIQUAC model. In these figures, the experimental data at 283.2, 303.2, and 323.2 K are plotted for water (1) + ethanol (2) + [bmim][PF6] (3), together with the experimental and calculated tie lines calculated using the UNIQUAC model. Even though a relatively good fit is attined for each temperature, the parameters determined for each temperature have no relation to each other. 3.3. Study of the Ability of ILs as Solvents. Although type II systems are not usually applied in industrial LLE applications, if there is another option, the applicability of [bmim][PF6] as a solvent in the separation of water/ethanol mixtures using LLE was studied, such that we are able to determine that the distribution coefficient, selectivity, and the behavior of the system at 323.2 K is practically type I. The solute distribution ratio provides the solvent capacity of the IL, which is related to the amount of IL required for the extraction process. The distribution coefficient was defined as

∑ ∑ ∑ (xijk − xijk̂ )2 k=1 j=1 i=1

0.800

(2)

The rmsd provides a measure of the agreement between the calculated and the experimental data. In Table 6 there can be observed a good agreement between UNIQUAC experimental data and correlations, indicating the reliability of the parameters obtained. The NRTL model obtained a slightly worse correlation for both systems. The 777



K2 =

Article

x 2,ILrichphase x 2,aqueousrichphase

[bmim][PF6] are worse than those obtained for [bmim][Tf2N] or [hmim][Tf2N]. As shown in Tables 3 to 5 and Figure 5, system behavior is singular. At 283.2 K the distribution coefficient remains below unity, and the selectivity starts with acceptable values at low ethanol concentrations but diminishes as the ethanol concentration rises. Furthermore, at 303.2 K, there are two immiscibility zones, and at 323.2 K, the immiscibility gap is too small. On the other hand, the selectivity at 283.2 and 303.2 K reaches values appropriate for extraction (from 4.306) involving low concentrations of ethanol, while at high concentrations of alcohol it becomes lower than the unity. At 323.2 K, the selectivity reaches values adequate for LLE involving low concentrations of ethanol. All of these considerations lead to the conclusion that the distribution coefficient and selectivity alone cannot be considered to work at a temperature greater that the ambient, especially at elevated ethanol concentrations. Moreover, as is shown in Figure 5, the distribution coefficient for the [bmim][Tf2N] or [hmim][Tf2N] is better, and these ILs present a type I behavior at all temperatures; therefore, they are more suitable for ethanol/water mixture separation.

(3)

where 2 is the ethanol and provided in Tables 3 to 5. The selectivity (S) could be used to evaluate the effectiveness of a solvent. In fact, the capability of the IL to separate the ethanol from the mixture is given by its selectivity and is defined by

S=

(x 2/x1)ILphase (x 2/x1)aqueousphase

(4)

where the subscript 1 represents water and 2 represents ethanol. The selectivity values for the system studied are shown in Tables 3 to 5. Figure 5a shows the effect of temperature on the water (1) + ethanol (2) + [bmim][PF6] (3) system. As can be observed,

4. CONCLUSIONS Understanding and developing the behavior of LLE in ternary systems with ILs is a critical first step in determining their ability to separate mixtures, such as alcohols and water. Furthermore, experimental data are essential to obtain reliable parameters for models, which can then be used to accurately simulate the process. The determination of the composition for the water (1) + ethanol (2) + [bmim][PF6] (3) system of the experimental tie lines at atmospheric pressure was carried out at 283.2, 303.2, and 323.2 K. Previously, some authors tried to use activity coefficient models to predict the type II behavior of a system without success. The UNIQUAC and NRTL equations were applied to modelate the equilibria data. Both models were found to properly correlate the data for the two systems studied, showing the type II behavior of system, but NRTL obtains a slightly worse result. The applicability of [bmim][PF6] as a solvent was studied using the selectivity and the distribution coefficient and was compared with other ILs reported in the literature. This comparison allows us to check the viability of LLE. This study concludes that the [bmim][PF6] could be an option for separating ethanol/water mixtures using LLE; however, more promising ILs are reported in the literature.

Figure 5. Distribution coefficient of ethanol between the extract and the raffinate phases for the water (1) + ethanol (2) system in different ionic liquids and temperatures: [bmim][PF6] this work at different temperatures: a) (○) 283.2 K, (□) 303.2 K, (△) 323.2 K; (b) comparison with other ILs from literature: (▲) [bmim][PF6] this work at 303.2 K, (●) [hmim][Tf2N]11 at 295.2 K, (◆) [bmim][Tf2N]12 at 303.2 K.

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Amparo Cháfer: 0000-0003-4287-1552

the distribution coefficient rises with increasing the temperature, but the values are all relatively low. Figure 5b shows the effect of the [bmim][PF6] in the distribution of ethanol (2) in both liquid phases at 303.2 K, and it is compared with data obtained from the literature for 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([bmim][Tf2N])18 and 1hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([hmim][Tf2N])17 at similar temperatures. The results for

Funding

The authors gratefully acknowledge the financial support from the Ministerio de Ciencia y Tecnologiá of Spain (project no. CTQ2010-18848/PPQ) and the Universitat de València (project no. UV-INV-AE15-340195) Notes

The authors declare no competing financial interest. 778



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