VaporâLiquid Phase Equilibria and Excess Thermal Properties of

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Vapor−Liquid Phase Equilibria and Excess Thermal Properties of Binary Mixtures of Ethylsulfate-Based Ionic Liquids with Water: New Experimental Data, Correlations, and Predictions Marta Królikowska,* Kamil Paduszyński, Marek Królikowski, Paweł Lipiński, and Jerzy Antonowicz Department of Physical Chemistry, Faculty of Chemistry, Warsaw University of Technology, Noakowskiego 3, 00-664 Warsaw, Poland S Supporting Information *

ABSTRACT: This work reports the measurements of the vapor pressure, excess enthalpy of mixing, and molar heat capacity for selected {ionic liquid + water} binary systems. The studied ionic liquids are 1-ethyl-1-methylpiperidinium ethylsulfate, 1-ethyl-1methylpyrrolidinium ethylsulfate, and 1-ethyl-1-methylmorpholinium ethylsulfate. The isothermal vapor−liquid phase equilibria have been measured by an ebulliometric method within temperature range from 338.15 to 368.15 K and pressure up to the vapor pressure of pure water. Excess enthalpy was measured with an isothermal titration calorimeter at temperature 298.15 K. Heat capacities have been determined within the temperature range from 288.15 to 383.15 K. The influence of temperature and composition as well as the structure of cation of the studied ionic liquids on the measured properties was assessed. The Redlich− Kister correlation was used in order to reduce the huge number of data points collected. Finally, thermodynamic modeling with molecular-based PC-SAFT equation of state was performed in order to check predictive capabilities of this model as well as to provide some physical insight into mutual ionic liquid−water interactions. for a working fluid pair for absorption refrigeration processes should exhibit negative deviations from ideal behavior; i.e., it should show vapor pressure depression compared to Raoult’s Law. It has been shown in numerous literature reports published previously that ILs can significantly reduce the saturated vapor pressure of refrigerants with different magnitudes depending on the selected cation−anion combination, temperature, and IL concentration.4−13 Several groups have also reported the HE for aqueous solution for different ILs.14−33 The exothermic effect of mixing with water (i.e., HE < 0), which is required for absorption refrigeration technologies, was observed for a great variety of ILs: 1-ethyl-3-methylimidazolium diethylphosphate, ethyl(tributyl)phosphonium dietylphosphate, 1-ethyl-3-methylimidazolium ethylsulfate, 1butyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium methanesulfonate, 1-ethyl-3-methylimidazolium trifluoroacetate, 1-(2-hydroxyethyl)-3-methylimidazolium trifluoroacetate, choline glycolate, choline lactate, 1-butyl-1-methylpiperidinium dicyanamide, and 1-butyl-1-methyl-pyrrolidinium dicyanamide. Finally, heat capacity, defined as the amount of heat that causes an increase in the sample temperature of 1 K, is one of the most important properties for thermal applications. In the literature, there is an extensive amount of data on the heat capacity of the pure ILs as a function of temperature.4,13−22,34−53 However, there are only few papers that report heat capacities of water with the following ILs: N-octylisoquinolinium thiocyanate, N-hexyl-isoquinolinium thiocyanate, 1-(2-hydroxylethyl)-3-methylimidazolium chloride, 1-

1. INTRODUCTION The absorption refrigeration technology which has been known for over 100 years arouses an interest of both academia and scientific communities around the world. The reason for this is that such an approach for refrigeration is environmental friendly and could make use of the low-grade energy. The absorption refrigeration is widely used in many fields, such as air conditioning, electric power supply, or chemical industry.1 The performance of absorption cycles involved in the adsorption refrigeration system depends on a number of process parameters, mostly on the physicochemical and thermodynamic properties of a working pair composed of absorbent and refrigerant. Typical working pairs employed by industry are {ammonia + water} and {lithium bromide + water} mixtures.2 However, there are some features of those systems that affect negatively the overall process efficiency, for instance, problems with crystallization and corrosion as well as unfavorable toxicological and eco-toxicological properties.3 This creates opportunities for some new systems, like those based on aqueous solutions of “green chemicals” such as ionic liquids (ILs). Over the past few years, many research groups have investigated the possible use of {IL + water} systems as alternative working pairs for absorption cycles. In order to know whether those have the potential to be effectively used as a working fluid in absorption refrigeration, it is necessary to know the thermodynamic properties such as vapor−liquid equilibrium (VLE) phase diagrams and excess thermal properties of mixing like excess enthalpy or heat of mixing (HE) and excess heat capacity (CpE). The VLE phase diagram of a binary system containing ILs is the most important factor to determine whether the binary solution is suitable for the absorption refrigeration system. In particular, a good candidate © XXXX American Chemical Society

Received: September 30, 2014 Revised: October 31, 2014 Accepted: November 3, 2014

A

dx.doi.org/10.1021/ie503872p | Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Industrial & Engineering Chemistry Research

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water mass fraction of the dried ILs was determined using Karl Fischer titration (model SCHOTT Instruments TitroLine KF), and it was found to be less than 1200 ppm for all samples. The thermophysical characterization of pure ILs have been done using DSC and TG/DTA techniques, and the density and dynamic viscosity at wide temperature and composition range and (solid + liquid) phase equilibria were presented in our latest paper.62 The chemical structures of the ionic liquids tested in this work are presented in Figure 1. Ultrapure water

ethyl-3-methylimidazolium dimethylphosphate, 1-butyl-3-methylimidazolium methylsulfate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium triflate, 1-butyl-3-methylimidazolium triflate, 1-ethyl-3-methyl-imidazolium trifluoroacetate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylpyridinium tetrafluoroborate, 1-butyl-1-methylpyrrolidinium tetrafluoroborate, and 1-butyl-3-methylimidazolium tetrafluoroborate. Besides systematic reports on the experimental data for {IL + water} binary mixtures, some efforts have been made in the field of modeling of these systems. Thus far, several thermodynamic tools have been applied to model phase equilibria of ILs-based systems, varying from simple correlative activity coefficient models like universal quasi-chemical approach (UNIQUAC)15 or universal functional groups activity coefficients (UNIFAC)54 to more sophisticated molecularbased equations of state allowing a more general thermodynamic description to be obtained as well as displaying enhanced predictive capacity. In particular, different methodologies based on statistical associating fluid theory (SAFT), in particular like perturbed-chain SAFT (PC-SAFT)55−57 and soft-SAFT,58,59 have been the most exhaustively studied models belonging to this family. Very recently, successful applications of these very promising models to VLE of several {IL + water} systems were demonstrated. Moreover, a conductor-like screening model for real solvents (COSMO-RS), based on unimolecular quantum chemical calculations, has been also investigated in recent years very intensively.60,61 In this work, isothermal VLE phase diagrams and HE and CpE data are reported for binary systems composed of water and three distinct ILs having the same ethylsulfate anion and the cation alkyl side chain length, while differing in cation core structure: 1-ethyl-1-methyl-piperidinium ethylsulfate, 1-ethyl-1methylpyrrolidinium ethylsulfate, and 1-ethyl-1-methyl-morpholinium ethylsulfate. Therefore, on the basis on the results obtained in this work, one can be able to draw some conclusions on an impact of IL’s cation type on the investigated properties. It is noteworthy that thermal, volumetric, and transport properties of pure ILs and {IL + water} systems as well as water-in-IL and IL-in-water solubility were presented by us previously.62 To our best knowledge, this work combined with the previous contribution summarize the very first such comprehensive study on those systems. All the experimental data collected have been correlated using the well-known Redlich−Kister correlation, in some cases incorporating temperature dependent coefficients. Moreover, the PC-SAFT equation of state was used in correlative and predictive mode to represent all kinds of thermodynamic data for the investigated systems as well as to make some inferences on mutual IL− water molecular interactions.

Figure 1. Chemical structures of the investigated ionic liquids.

was deionized by a reverse osmosis unit with an ion-exchange system (Cobrabid-Aqua, Poland) and next degassed in an ELMA Germany ultrasonic bath at about 320 K before each measurement. 2.2. Apparatus. 2.2.1. Vapor−Liquid Phase Equilibrium Measurements. The isothermal VLE data for the tested binary mixtures have been determined using an ebulliometric method. The vapor pressure, P, as a function of the IL mole fraction in the liquid phase, x1, was reported at constant temperature, T. Due to the extremely low volatility of the IL, the vapor phase is composed only of solvent in the studied system. The ebulliometer, designed by Rogalski and Malanowski, was used and described earlier.63 This apparatus was connected to the pressure stabilizing system consisting of the thermostated container with volume of 50 dm3 enabling the pressure to be kept constant within ±0.1 kPa and to dampen the pressure fluctuations caused by the bumping of the liquid boiling in the ebulliometer or by the variation of the temperature of the surroundings. The equilibrium temperature was measured with a resistance thermometer (type P-550, ROTH, Germany) with the precision ±0.01 K. The pressure was measured with the precision ±0.1 kPa by a tensiometric vacuum meter (type CL 300, ZEPWN, Poland). The composition of the liquid phase was determined using the Anton Paar GmbH 4500 vibratingtube densimeter (Graz, Austria) with an accuracy of ±10−5 g· cm−3 at different temperatures. A calibration curve of density vs mole fraction of IL was made and the uncertainty in the mole fraction composition was better than 2 × 10−3. The uncertainty of the method used for the VLE estimation is larger than the instruments error and was estimated as ±0.5 kPa. The experiments have been carried out in the mole fraction range from pure water (x1 = 0) to x1 = 0.158, 0.213, and 0.053 of [EMPIP][EtSO4], [EPYR][EtSO4], and [EMMOR] [EtSO4], respectively. Upon further increase of ionic liquid mole fraction, results in overheating and bumping of the sample and give

2. EXPERIMENTAL SECTION 2.1. Materials. The names and corresponding abbreviations used henceforth for the ILs studied in this work are as follows: 1-ethyl-1-methylpiperidinium ethylsulfate, [EMPIP][EtSO4], 1ethyl-1-methylpyrrolidinium ethylsulfate, [EMPYR][EtSO4], or 1-ethyl-1-methylmorpholinium ethylsulfate, [EMMOR][EtSO4]. The ILs were purchased from IoLiTec (Ionic Liquids Technologies GmbH, Germany) as custom syntheses. The supplier declared the final purity of all the samples as higher than 97%. Prior to each measurement the samples of ILs were degassed using ultrasonic bath and dried in vacuum at T = 343 K for 48 h in order to eliminate volatile compounds. Then, the B



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(99.999%) indium was used to calibrate the temperature and cell constant. The heat capacity calibration constant was derived from MDSC measurements of pure water by calculating a ratio of experimental to theoretical value of water heat capacity. Liquid samples were sealed in ambient air in hermetic aluminum pans having mass of about 50 mg, and an empty hermetic aluminum pan was used as a reference. A sample size of about 20 mg was used throughout this study, and the heat flow was normalized by the actual weight of each sample. Better accuracy of the experiment was ensured by including in heat flow calculation the actual weights of sample and reference pans. The conditions of the MDSC experiments were as follows: 2 K·min−1 heating rate, 1 K sinusoidal temperature modulation amplitude, and 120 s modulation period. The MDSC data were analyzed using TA Universal Analysis software. Specific heat capacity was derived from the ratio of the heat flow and heating rate amplitudes applying a simple deconvolution procedure.

unreliable data. Despite the fact that the investigated range of concentrations might be viewed as relatively narrow, the corresponding ranges expressed on a mass fraction basis are much broader, namely, from to pure water to 0.742, 0.782, and 0.445 for piperidinium, pyrrolidinium, and morpholinium-based IL, respectively. 2.2.2. Excess Enthalpy Measurements. Isothermal titration calorimeter (ITC, Model TAM III, TA Instruments) was used to determine the excess enthalpies of mixing (HE). The calorimeter consists of two cells: titration and reference, which are placed in the test wells of the thermostatic oil bath. Before each experiment, the temperature of the bath was maintained for 24 h at 298.15 K with a stability of ±100 μK. Due to the very high viscosity of pure ionic liquids,62 it was impossible to take measurements over the entire range of composition. About 0.5 cm3 of the liquid sample with a specific composition (x1 = 0.79 for [EMPIP][EtSO4], x1 = 0.74 for [EMPYR][EtSO4], and x1 = 0.75 for [EMMOR][EtSO4]) was placed in the titration cell, placed in a thermostated oil bath, and equilibrated for a few hours. Depending on the change in mole fraction of the IL, 0.002−0.015 ± 0.001 cm3 of water was injected using a precise syringe pump into the titration cell. During the titration, the binary mixture was rigorously stirred with stirring speed of 100 rpm. The molar amount of the water, required to calculate the mole fraction of solution, was calculated on the basis of the volume with the known density, determined with an uncertainty of ±5 × 10−5 g·cm−3 at T = 298.15 K ± 0.01 K using vibrating tube densitometer (DMA 4500, Anton Paar, Austria). The actual property measured by TAM III is the difference in heat flow between sample and reference cells. Uncertainty of this measurement is about ±0.2%. Each injection is associated with the heat flow peak on the power−time curve. Integration of the heat flow peak results in the total amount of heat effect during the jth injection (δqj). This quantity is readily transformed into total molar excess enthalpy of mixing for a concentration obtained by the ith injection (HiE): i

HiE =

∑ j=1

3. THERMODYNAMIC MODELING 3.1. Redlich−Kister Correlations. Excess properties of mixing for the investigated systems, namely, GE, HE, and CpE, were reproduced by using the well-known Redlich−Kister (RK) expansion: k−1

XE = x1x 2 ∑ Ai (T )(x 2 − x1)i RT i=0

where X = G, H, Cp, whereas T stands for the absolute temperature, x1 and x2 stand for mole fractions of the mixture components (1 = IL, 2 = water; x2 = 1 − x1), and R denotes the universal gas constant (if X = CpE, then R is placed in denominator instead of RT). In order to increase the accuracy of the final correlations, the RK coefficients Ai were allowed to be dependent on temperature, according to the following relationship: Ai (T ) = ai(0) + ai(1)(T , K)

δqj

(3)

Excess enthalpy and heat capacity data were analyzed directly in terms of eq 3. In turn, the expression for excess Gibbs free energy (GE) was used to determine liquid phase activity coefficient of water (γ2) in the {IL + water} system by applying the following thermodynamic formula:

i

n1 + ∑ j = 1 Δn2, j

(2)

(1)

where n1 is the number of moles of IL and Δn2,j is the number of moles of solute injected during the jth titration. The reliability of our calorimetric experiments was verified by performing the test measurements at T = 298.15 K for two reference systems: {methanol + water} and (cyclohexane + nhexane}. Those systems exhibit negative (exothermic) and positive (endothermic) heat effects of mixing, respectively. The results obtained were compared to available literature data, and an excellent agreement was observed.64 Finally, the overall uncertainty of the data determined in the present study is estimated to be less than 0.5% in which uncertainty of composition is also included. 2.2.3. Heat Capacity Measurements. Modulated differential scanning calorimetry65 (MDSC) technique was used to determined isobaric heat capacities (Cp) for the tested binary systems. The experiments were performed over a wide temperature range from 288.15 to 343.15 K using a DSC Q2000 (TA Instruments) calorimeter equipped with a liquid nitrogen cooling system and operating in heat-flux mode. The sample cell was constantly fluxed with high purity helium gas at a constant flow rate of 25 cm3·min−1. Heat flow calibration was performed using standard sapphire samples. High purity

⎛ ∂GE /RT ⎞ ln γ2 = GE /RT + x1⎜ ⎟ ⎝ ∂x 2 ⎠T

(4)

Then, the activity coefficients were employed in the vapor− liquid equilibrium calculations. Since IL is considered as a compound having negligible vapor pressure, the following thermodynamic equilibrium condition connecting the system’s temperature (T), pressure (P), and IL concentration (x1) holds: P = (1 − x1)γ2(x1 , T )P2sat(T )

(5) sat

Vapor pressure of pure water, denoted in eq 5 as P2 (T), was calculated from the DIPPR 801 correlation.66 Such an assumption does not affect calculations significantly compared to calculations employing experimental pure-water vapor pressure. Besides, eq 5 coupled with the DIPPR 801 is insensitive toward pure-fluid experimental data and thus the final RK correlation can be easily used to extrapolate/ interpolate VLE calculations to different temperatures. C



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components, the parameters are as follows: number of segments forming the chain (m), the segment hard-sphere diameter (σ), and dispersive interactions energy (u/kB). For chemicals composed of molecules interacting via hydrogen bonding, the associating sites and so-called association scheme (number, types, and pairing of the sites) must be defined. Then two additional parameters are introduced, namely, the association energy and relative volume (εAB/kB and κAB, respectively), in order to describe a particular specific interaction between site of type A and site of type B. A common and well-established procedure for calculating the PCSAFT parameters rests on fitting the model predictions to experimental pure-fluid properties such as liquid density and/or vapor pressure. In order to extend the PC-SAFT to mixtures, so-called combining rules are necessary. They are simple mathematical expressions relating model parameters assigned to interactions between like and unlike molecules. The potential well depth for dispersion interaction between segments of molecules of types 1 and 2 (u12/kB) and the segment diameter assigned to this interaction (σ12) are usually calculated by using the conventional combining rules of Lorentz−Berthelot:

It is noteworthy that vapor-phase nonidealities have not been taken into account in eq 5. Usually such a simplification is perceived as reasonable, when the pressure of the system is relatively lowas in the case of the studied mixtures, for which P < 100 kPa. Finally, eq 5 combined with eqs 2−4 can be directly used to obtain vapor pressure if the system’s temperature and composition as well as RK coefficients are known. The latter ones have been optimized by means of minimization of the following objective function: N

OF =

∑ (Xicalcd − Xiexptl)2 i=1

(6)

where N stands for number of experimental data points. For this purpose, a nonlinear least-squares procedure involving the Levenberg−Marquardt algorithm was adopted. It is important to note that we attempted to use a single set of parameters in eq 2 to calculate all the investigated propertiesin fact, it could be done due to mutual relationships between all the measured properties arising from common thermodynamic formulas. Unfortunately, the RK correlation was not sufficiently flexible to fit such complex behavior as that observed for the investigated systems, and hence, distinct sets of RK coefficients are provided for each property separately. 3.2. PC-SAFT Modeling. The PC-SAFT method published by Gross and Sadowski67,68 in the beginning of the 2000s is nowadays one the most promising thermodynamic tools for correlation and predication of different thermodynamic properties of a great variety of systems, including simple mixtures of compounds based on small and symmetric molecules as well as complex asymmetric systems exhibiting significant deviations from Raoult’s law. The theory based on the thermodynamic perturbation theory (TPT) of Wertheim69−72 pictures real molecules as molecular chains consisting of a given number spherical segments and interacting via short-range physical forces like van der Waals dispersive forces as well as strong and highly directional specific donor−acceptor interactions or hydrogen bonds. The PC-SAFT model separates different contributions to residual Helmholtz energy (Ares) corresponding to respective molecular interactions. The most common form of the major expression is as follows: Ares Ahc Adisp Aassoc = + + + ... NkBT NkBT NkBT NkBT

u12 =

u1u 2 ,

σ12 =

σ1 + σ2 2

(8)

In the case of cross-associating systems, the combining rules for the energy and volume of the respective cross-associations are required. For that purpose, the relations proposed by Wolbach and Sandler74 can be utilized: ε

A1B2

ε A1B1 + ε A 2B2 , = 2

κ

A1B2

=

κ

A1B1 A 2B2

κ

⎛ 2 σ1σ2 ⎞3 ⎟ ⎜ ⎝ σ1 + σ2 ⎠ (9)

In eq 3, Ai and Bj denote site of type A on molecule i (i = 1, 2) and site of type B on molecule j (j = 1, 2). It is noteworthy that the Wolbach−Sandler expressions have been originally used by Gross and Sadowski.68 Provided that the pure fluid parameters are known, the PCSAFT model combined with eqs 2 and 3 can be used to describe mixtures in an entirely predictive manner. However, a good accuracy can be achieved only for relatively simple systems composed of nonpolar moieties. In order to make the quality of predictions better, binary interaction parameters (denoted by k12LB and k12WS, respectively) are introduced by adopting the following definitions:

(7)

where N stands for number of molecular chains and kB for the Boltzmann constant. Superscripts “hc”, “disp”, and “assoc” denote contributions due to hard-chain formation (the reference system for TPT), dispersive interactions between chains, and association (the perturbations), respectively. Other relevant thermodynamic properties (like pressure, enthalpy, and activity) can be easily derived by differentiating eq 7 with respect to a selected state variable following some basic rules of thermodynamics. Detailed discussion on expressions and working equations of PC-SAFT will not be shown in this article because they can be found elsewhere, either in the original papers of Gross and Sadowski67 or in an excellent compilation of Folas and Kontogeorgis.73 Here we briefly present the model parameters only and demonstrate how to apply the PC-SAFT approach to both pure and mixed fluids. In terms of the model, each pure component is characterized by at least three parameters. In the case of nonassociating

u12 =

LB u1u 2 (1 − k12 )

ε A1B2 =

ε A1B1 + ε A 2B2 (1 − k12WS) 2

(10)

The major drawback of introducing k12LB and/or k12WS corrections is that they are usually fitted to experimental data on binary systems. Hence, the predictive capacity of the model is limited, and it can be viewed as a correlative tool. Nevertheless, the binary corrections determined based on one particular type of data can be used to calculate other thermodynamic properties with a good (sometimes even an excellent) accuracy. For example, one can adopt the binary corrections fitted to VLE data in order to predict excess properties like HE or CpE. This is actually presented in further sections of this work. D



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[EMPYR][EtSO4]. The values of the minimum HE are equal to −675.4 J mol−1 (x1 = 0.2000), −1255.1 J mol−1 (x1 = 0.2051), and −1614.9 J mol−1 (x1 = 0.2427) for [EMMOR][EtSO4], [EMPIP][EtSO4], and [EMPYR][EtSO4], respectively. The negative values of the excess enthalpy suggest that the interactions between IL and water are stronger than the corresponding IL-IL and water−water interactions. This is mainly due to strong interactions between water and ethylsulfate anion, which was also observed in literature.39 The negative values of the excess enthalpies are especially required for the working pair of the absorption heat pump or refrigeration. The experimental data of molar heat capacity, Cp, determined for {IL + water} binary systems as a function composition at temperatures from 278.15 to 383.15 K are listed in Tables S3− S5 in the Supporting Information. In particular, molar heat capacity of pure ILs can as a function of temperature can be described by using the following polynomial expressions: [EMPIP][EtSO4]

4. RESULTS AND DISCUSSION 4.1. Experimental Data. The vapor−liquid phase equilibria of binary solutions of [EMPIP][EtSO4], or [EMPYR] [EtSO4], or [EMMOR][EtSO4] with water were measured within the temperature range from 338.15 to 368.15 K and pressures from 20 to 85 kPa for different ionic liquid mole fractions. All the experimental results are listed in Table S1 in the Supporting Information. Representative results for each system studied are shown in Figure 2. As can be easily noticed, the higher the

Cp , J·K−1·mol−1 = 236.8 + 0.6424(T , K)

(11a)

[EMPYR][EtSO4] Cp , J·K−1·mol−1 = 285.6 + 0.4426(T , K) Figure 2. Vapor pressure of {IL + water} mixtures (P) as a function of ionic liquid mole fraction (x1) and temperature (T). Solid lines have been designated by the Redlich−Kister correlation.

(11b)

[EMMOR][EtSO4] Cp , J·K−1·mol−1 = 306.267 + 0.4770(T , K)

(11c)

It was observed that the molar heat capacities of pure ILs are much higher than that of water and vary approximately from 75 to 76 J·K−1·mol−1 over the whole range of temperatures under consideration; see Figure 4. Therefore, CpE of aqueous

content of ILs, the larger the deviation from Raoult’s law. These solutions containing [EMPIP][EtSO4], [EMPYR][EtSO4], and [EMMOR][EtSO4] exhibit a strong ability to absorb the refrigerant, which is a very important property of a working pair for the absorption heat pump and absorption refrigeration. The full list of experimental values of excess enthalpies (HE) of the {IL + water} binary mixtures as a function of IL mole fraction at temperature T = 298.15 K are collected in Table S2 in the Supporting Information. The data are graphically shown in Figure 3. It is important to note that all binary mixtures tested in this work exhibit negative values of the excess enthalpies at T = 298.15 K, which is connected with exothermic mixing effect. The minimum of the HE arranged in the following order: [EMMOR][EtSO4] > [EMPIP][EtSO4] >

Figure 4. Molar heat capacity (Cp) of pure ionic liquids under study as a function of temperature. Solid lines determined by polynomial fits given in eq 11.

solutions of the studied ILs decreases with increasing of water content at given temperatures. The value of molar heat capacities for pure ILs are arranged in the following order: [EMMOR][EtSO4] > [EMPIP][EtSO4] > [EMPYR][EtSO4], and at temperature T = 298.15 K the Cp are equal to 448.4 J· mol−1·K−1 (1.756 J·g−1·K−1); 428.1 J·mol−1·K−1 (1.690 J·g−1· K−1); and 417.2 J·mol−1·K−1 (1.743 J·g−1·K−1), respectively. Besides, the heat capacities slightly decrease with increasing of temperature at the same IL concentration. Apart from that, the C p of pure IL significantly increases with increasing temperature, whereas the value of heat capacity of water is

Figure 3. Excess enthalpy of mixing of {IL + water} mixtures (HE) as a function of ionic liquid mole fraction (x1) and temperature (T). The solid lines have been designated by the Redlich−Kister correlation. E



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optimized coefficients are listed along with the values of rootmean-square deviations (RMSD):

almost constant in the measured temperature range. This affects the values of heat capacity for the solution. From the experimental Cp data, the corresponding CpE were calculated for all binary mixtures investigated in this work. The obtained CpE vs ionic liquid mole fraction data at selected temperatures for all three binary systems are plotted in Figure 5. In particular, the

RMSD =

∑ (Xicalcd − Xiexptl)2 N−k

(12)

where N stands for number of experimental data points, while k denotes the number of adjustable parameters used during fitting process. The results are also shown in Figures 2−5. As can be seen, the proposed correlations are capable of accurately capturing all the properties under study over a broad range of temperature and IL concentrations. Thus, they can be used for interpolation/extrapolation purposes, if one is interested in thermodynamic properties of the studied systems at conditions different than those covered by the reported experimental data. It is noteworthy that a single RK coefficient per system was required in the case of VLE data (Figure 6a), whereas in the case of HE at least four coefficients were necessary to reproduce the calorimetric data with a satisfactory accuracy (Figure 6b). Finally, in the case of CpE, a three temperature-dependent coefficients (thus, six parameters in total, see eq 3) were adopted (Figure 6c). PC-SAFT modeling was also carried out for the three investigated systems. First, the molecular scheme for ethylsulfate-based ILs was defined. We decided to mimic the molecular structure of each IL as a chain electro-neutral chain having several associating sites attached. Such a framework for SAFT modeling of IL-based systems, i.e., treating ILs as nonionic moieties, has become very popular recently. It was tested in our previous papers55,64 as well as in the contributions of other research groups.56−59 Therefore, we decided to transfer it to ILs having in their structure hydrophilic [EtSO4] anion. The number of negative (acceptor) associating sites attached to each molecular chain was set to the value of seven, which corresponds to the number of lone pairs present in the anion’s structure. The number of positive (donor) sites was also fixed as seven for each IL. In other words, we assumed that the IL ion-pair has an accepting capability to the same extent as it has a donating capability. Thus, the finally adopted associating scheme for all the ILs was “7 + 7”.

Figure 5. Excess molar heat capacity of mixing of {IL + water} mixtures (CpE) as a function of ionic liquid mole fraction (x1) and temperature (T). Solid lines have been designated by the Redlich− Kister correlation.

{[EMPYR][EtSO4] + water} binary system exhibits negative CpE at lower temperatures up to T = 318.15 K, followed by Sshape behavior at intermediate temperatures and finally positive CpE at temperatures higher than T = 348.15 K. Similar behavior was observed for the [EMMOR][EtSO4] IL. In the case of [EMPIP][EtSO4], either S-shape at low temperatures (T < 318.15 K) or positive CpE at higher temperatures over the entire range of IL concentrations was observed. 4.2. Modeling. All the experimental data were correlated with RK correlations given in eqs 2 and 3. The results of the fitting procedure are shown in Table 1, where RK the

Table 1. Optimized Values of Redlich−Kister Correlation Coefficients Representing the Investigated Properties (see eqs 2 and 3) and the Respective Values of Root Mean Square Deviations (RMSD) (see eq 12)

Vapor−Liquid Equilibrium (VLEGE) a0(0) RMSD, kPa Excess Enthalpies (HE) a0(0) a1(0) a2(0) a3(0) a4(0) RMSD, J·mol−1 Excess Heat Capacities (CpE) a0(0) a0(1) a1(0) a1(1) a2(0) a2(1) RMSD, J·K−1·mol−1

[EMPIP][EtSO4]

[EMPYR][EtSO4]

[EMMOR][EtSO4]

−9.1553 0.47

−6.6212 0.79

−11.654 0.26

−1.0853 −1.6082 −1.8951 −1.5692 −0.6876 3.86

−1.8828 −1.8293 −1.9434 −1.4684

−0.5854 −0.8921 −1.2205 −0.6549

5.79

1.98

2.7203 0.0668 9.5255 0.0533 1.0240 0.1344 1.36

−2.4199 0.0702 3.5996 0.0101 −0.9032 0.1077 0.27

−1.8910 0.0523 −2.2848 −0.0275 0.3403 0.0393 0.43

F



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enthalpy at T = 298.15 K was reported for this IL by Armstrong et al.75 The reported value 164 kJ·mol−1 can be used to obtain Hildebrand solubility parameter of this IL at T = 298.15 K, δ = 28.60 MPa1/2. By using this value and complementary density data easily available in the literature, we obtained the set of PCSAFT parameters for [EMIM][EtSO4]: m = 7.9174, σ = 3.3343 Å, u/kB = 189.771 K, εAB/kB = 1665.40 K, κAB = 0.0598 (AARD in density and solubility parameter less than 0.1%). The values of m, u/kB, εAB/kB, and κAB were transferred to [EMPIP][EtSO4], [EMPYR][EtSO4], and [EMMOR][EtSO4] assuming that all the ILs are of a similar size as [EMIM][EtSO4] and display similar energies of intermolecular interactions. Finally, the only parameter adjusted in the fitting process was the segment-diameter σ. The values obtained for [EMPIP][EtSO4] [EMPYR][EtSO4], and [EMMOR][EtSO4] were σ = 3.4657, 3.3950, and 3.4073 Å, respectively, with the values of AARD in density at the level of 0.1%. Having the ILs parametrized, the properties of mixtures can be predicted. In our calculations 4C model for water was employed and the PC-SAFT parameters were taken from literature.76 Unfortunately, “pure” predictions (i.e., k12LB = k12WS = 0) yielded poor results. However, when a single (and temperature-independent) Wolbach−Sandler binary correction (see eq 10) was fitted to VLE data, the model exhibited a nice correlative capacity over the entire range of composition and temperature under study; see Figure 6a. The values of k12WS fitted in this study are −0.0715, −0.0556, and −0.0547 for mixtures of water with [EMPIP][EtSO4], [EMPYR][EtSO4], and [EMMOR][EtSO4], respectively. What is interesting is that the obtained values are of similar order of magnitude. It is noteworthy that the binary corrections to Lorentz−Berthelot combining rules (see eq 10) were not employed. Indeed, we checked that incorporation of additional parameter k12LB does not improve the quality of fit significantly. The binary corrections fitted to VLE were used to predict HE and CpE. The results are shown in Figure 6b,c, respectively. As seen, PC-SAFT is capable of capturing the behavior of the studied systems only qualitatively. In the case of HE, exothermic mixing is predicted by the model for all three ILs under consideration. The worst accuracy was achieved for [EMPYR][EtSO4]. Finally, CpE of the studied systems is underestimated by the PC-SAFT by about 1 order of magnitude, as seen for [EMPYR][EtSO4] shown as an example in Figure 6c. However, despite the fact that the predicted values are much smaller compared to experiment, the model captures the S-shape dependence nicely. It can be seen as a satisfactory result taking into account simplicity of the molecular schemes adopted as complexity of the real molecular systems. It should be noted that this is the very first study, where PC-SAFT calculations for IL-based systems confront three types of experimental data determined within the same work. In particular, to our best knowledge this is also the very first contribution reporting CpE predictions for these systems.

Figure 6. Experimental data (markers) vs PC-SAFT correlated/ predicted thermodynamic data (solid lines) considered in this work. (a) Vapor−liquid equilibrium phase diagrams for {IL + water} systemscorrelations by using single binary correction (see details in text); (b) prediction of excess enthalpy of mixing; (c) prediction of excess molar heat capacity of mixing.

In the case of the studied ILs, liquid densities are the only data available that can be used to fit the PC-SAFT model parameters. However, PC-SAFT parameters determined from density data only may be seen as unreliable, because other properties are more sensitive toward some specific parameters (e.g., pure-fluid vapor pressure depends strongly on u/kB). Therefore, we decided to include the data for other ILs based on the [EtSO4] anion to the parametrization process. For that purpose we consider the mostly characterized IL from this family, namely, 1-ethyl-3-methylimidazolium ethylsulfate, [EMIM][EtSO4]. Besides densities over a wide range of temperature and pressure, there are some other kinds of data that can be found for this IL. In particular, vaporization

5. CONCLUSIONS In this work, three binary systems composed of ILs based on ethylsulfate anion and water have been considered as a new working pair for absorption refrigeration. Properties of aqueous solutions of the ILs such as vapor−liquid equilibrium phase diagrams, excess enthalpy, and excess heat capacity were determined. Moreover, Redlich−Kister correlations of the measured data were presented and modeling of the G



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(6) Peng, Y.; Fu, J.; Lu, X. Isobaric Vapor - Lliquid Equilibrium for Water + Acetic Acid + 1-Butyl-3-methylimidazolium Dibutylphosphate at 101.32 kPa. Fluid Phase Equilib. 2014, 363, 220−227. (7) Kim, Y. J.; Kim, S.; Joshi, Y. K.; Fedorov, A. G.; Kohl, P. A. Thermodynamic Analysis of an Absorption Refrigeration System With Ionic - Liquid/Refrigerant Mixture as a Working Fluid. Energy 2012, 44, 1005−1016. (8) Wu, X.; Li, J.; Fan, L.; Zheng, D.; Dong, L. Vapor Pressure Measurement of Water + 1,3-Dimethylimidazolium Tetrafluoroborate System. Chin. J. Chem. Eng. 2011, 19, 473−477. (9) Calvar, N.; Gonzalez, B.; Gomez, E.; Dominguez, A. Vapor Liquid Equilibria for the Ternary System Ethanol + Water + 1-Butyl-3methylimidazolium Methylsulfate and the Corresponding Binary Systems at 101.3 kPa. J. Chem. Eng. Data 2009, 54, 1004−1008. (10) Calvar, N.; Gonzalez, B.; Gomez, E.; Dominguez, A. Vapor Liquid Equilibria for the Ternary System Ethanol + Water + 1-Ethyl-3methylimidazolium Ethylsulfate and the Corresponding Binary Systems Containing the ionic liquid at 101.3 kPa. J. Chem. Eng. Data 2008, 53, 820−825. (11) Jiang, X.-C.; Wang, J.-F.; Li, C.-X.; Wang, L.-M.; Wang, Z.-H. Vapour Pressure Measurement for Binary and Ternary Systems Containing Water Methanol Ethanol and an Ionic Liquid 1-Ethyl-3ethylimidazolium Diethylphosphate. J. Chem. Thermodyn. 2007, 39, 841−846. (12) Wang, J.-F.; Li, C.-X.; Wang, Z.-H.; Li, Z.-J.; Jiang, Y.-B. Vapor Pressure Measurement for Water, Methanol, Ethanol, and Their Binary Mixtures in the Presence of an Ionic Liquid 1-Ethyl-3methylimidazolium Dimethylphosphate. Fluid Phase Equilib. 2007, 255, 186−192. (13) Kim, K.-S.; Park, S.-Y.; Choi, S.; Lee, H. Vapor Pressures of the 1-Butyl-3-methylimidazolium Bromide + Water, 1-Butyl-3-methylimidazolium Tetrafluoroborate + Water, and 1-(2-Hydroxyethyl)-3methylimidazolium Tetrafluoroborate + Water Systems. J. Chem. Eng. Data 2004, 49, 1550−1553. (14) González, B.; González, E. J. Physical Properties of the Pure 1Methyl-1-Propyl-pyrrolidinium Bis(trifluoromethylsulfonyl)imide Ionic Liquid and Its Binary Mixtures With Alcohols. J. Chem. Thermodyn. 2014, 68, 109−116. (15) Królikowska, M.; Paduszyński, K.; Zawadzki, M. Measurements, Correlations and Predictions of Thermodynamic Properties of Binary Mixtures of N-Octylisoquinolinium Thiocyanate and Its Aqueous Solutions. J. Chem. Eng. Data 2013, 58, 285−293. (16) Gomez, E.; Calvar, N.; Macedo, E. A.; Dominguez, A. Effect of the Temperature on the Physical Properties of Pure 1-Propyl-3Methylimidazolium Bis(trifluoromethylsulfonyl)-imide and Characterization of Its Binary Mixtures With Alcohols. J. Chem. Thermodyn. 2012, 45, 9−15. (17) Nie, N.; Zheng, D.; Dong, L.; Li, Y. Thermodynamic Properties of the Water + 1-(2-Hydroxylethyl)-3-methylimidazolium Chloride System. J. Chem. Eng. Data 2012, 57, 3598−3603. (18) Paulechka, Y. U.; Kabo, A. G.; Blokhin, A. V.; Kabo, G. J.; Shevelyova, M. P. Heat Capacity of Ionic Liquids: Experimental Determination and Correlations With Molar Volume. J. Chem. Eng. Data 2010, 55, 2719−2724. (19) Lin, P.-Y.; Soriano, A. N.; Caparanga, A. R.; Li, M.-H. Molar Heat Capacity and Electrolytic Conductivity of Aqueous Solutions of [Bmim][MeSO4] and [Bmim][triflate]. Thermochim. Acta 2009, 496, 105−109. (20) Crosthwaite, J. M.; Muldoon, M. J.; Dixon, J. K.; Anderson, J. L.; Brennecke, J. F. Phase Transition and Decomposition Temperatures, Heat Capacities and Viscosities of Pyridinium Ionic Liquids. J. Chem. Thermodyn. 2005, 37, 559−568. (21) Kim, K.-S.; Shin, B.-K.; Lee, H.; Ziegler, F. Refractive Index and Heat Capacity of 1-Butyl-3-methylimidazolium Bromide and 1-Butyl3-methylimidazolium Tetrafluoroborate, and Vapor Pressure of Binary Systems for 1-Butyl-3-methylimidazolium Bromide + Trifluoroethanol and 1-Butyl-3-methylimidazolium Tetrafluoroborate + Trifluoroethanol. Fluid Phase Equilib. 2004, 218, 215−220.

thermodynamic behavior was carried out with molecular-based PC-SAFT model. On the basis of the results obtained some influence of both cation and anion structures on general trends governing the properties were established and discussed. Experimental data, correlations, and predictions presented in this work can be very useful from the point of view of process design and operation. They revealed that the studied ILs may be promising candidates for modern absorption refrigeration processes as they exhibit desirable properties when mixed with water. Apart from that, these data (including experiments and modeling) may be viewed as a source of purely scientific information about the mutual affinity between IL and water in aqueous solutions.

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ASSOCIATED CONTENT

S Supporting Information *

Experimental vapor−liquid phase equilibrium data as a function of IL mole fraction and temperature, Table S1. Experimental excess enthalpy data as a function of IL mole fraction at temperature T = 298.15 K at atmospheric pressure, Table S2. Experimental Heat capacity and excess molar heat capacity as a function of IL mole fraction and temperature at atmospheric pressure, Tables S3−S5. This material is available free of charge via the Internet at http://pubs.acs.org/.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Fax: +48-22-628 27 41. Tel.: +48-22-234 56 40. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS Funding for this research was provided by the National Science Centre in years 2011−2014 (Grant No. 2011/01/D/ST5/ 02760). M.K. wishes to thank the support of the European Union in the framework of European Social Fund through the Warsaw University of Technology Development Programme. K.P. kindly acknowledges the support of the Foundation for Polish Science within the framework of START 2014 Program.

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REFERENCES

(1) Liang, S.; Chen, W.; Cheng, K.; Guo, Y.; Gui, X. The Latent Application of Ionic Liquids in Absorption Refrigeration. Applications of Ionic Liquids in Science and Technology; Handy, P. S., Ed.; InTech: Middle Tennessee State University, USA, 2011; pp 467−494. (2) Zhuo, C. Z.; Machielsen, C. H. M. Thermophysical Properties of the Trifluoroethanol-pyrrolidone System for Absorption Heat Transformers. Int. J. Refrig. 1993, 16, 357−363. (3) Aphornratana, S.; Chungpaibulpatana, S.; Srikhirin, P. Experimental Investigation of an Ejector Refrigerator: Effect of Mixing Chamber Geometry on System Performance. Int. J. Energy Res. 2001, 25, 397−411. (4) Fredlake, C. P.; Crosthwaite, J. M.; Hert, D. G. Thermophysical Properties of Imidazolium-Based Ionic Liquids. J. Chem. Eng. Data 2004, 49, 954−964. (5) Passos, H.; Khan, I.; Mutelet, F.; Oliveira, M. B.; Carvalho, P. J.; Santos, L. M. N. B. F.; Held, C.; Sadowski, G.; Freire, M. G.; Coutinho, J. A. P. Vapor - Liquid Equilibria of Water + Alkylimidazolium - Based Ionic Liquids: Measurements and Perturbed - Chain Statistical Associating Fluid Theory Modeling. Ind. Eng. Chem. Res. 2014, 53, 3737−3748. H



Article

the Ionic Liquid 1-Ethyl-3-methylimidazolium Dimethylphosphate. J. Chem. Thermodyn. 2011, 43, 576−583. (40) Ficke, L. E.; Novak, R. R.; Brennecke, J. F. Thermodynamic and Thermophysical Properties of Ionic Liquid + Water Systems. J. Chem. Eng. Data 2010, 55, 4946−4950. (41) Gracía-Miaja, G.; Troncoso, J.; Romaní, L. Excess Enthalpy, Density, and Heat Capacity for Binary Systems of Alkylimidazolium Based Ionic Liquids + Water. J. Chem. Thermodyn. 2009, 41, 161−166. (42) Blokhin, A. V.; Paulechka, Y. U.; Strechan, A. A.; Kabo, G. J. Physicochemical Properties, Structure, and Conformations of 1-Butyl3-methylimidazolium Bis(trifluoro-methanesulfonyl)imide [C4mim]NTf2 Ionic Liquid. J. Phys. Chem. B 2008, 112, 4357−4364. (43) Ficke, L. E.; Rodríguez, H.; Brennecke, J. F. Heat Capacities and Excess Enthalpies of 1-Ethyl-3-methylimidazolium-Based Ionic Liquids and Water. J. Chem. Eng. Data 2008, 53, 2112−2119. (44) Ge, R.; Hardacre, C.; Jacquemin, J.; Nancarrow, P.; Rooney, D. W. Heat Capacities of Ionic Liquids as a Function of Temperature at 0.1 MPa. Measurement and Prediction. J. Chem. Eng. Data 2008, 53, 2148−2153. (45) Bandrés, I.; Giner, B.; Artigas, H.; Royo, F. M.; Lafuente, C. Thermophysic Comparative Study of Two Isomeric Pyridinium Based Ionic Liquids. J. Phys. Chem. B 2008, 112, 3077−3084. (46) Strechan, A. A.; Paulechka, Y. U.; Kabo, A. G.; Blokhin, A. V.; Kabo, G. J. 1-Butyl-3-methylimidazolium Tosylate Ionic Liquid: Heat Capacity, Thermal Stability, and Phase Equilibrium of Its Binary Mixtures With Water and Caprolactam. J. Chem. Eng. Data 2007, 52, 1791−1799. (47) García-Miaja, G.; Troncoso, J.; Romaní, L. Density and Heat Capacity as a Function of Temperature for Binary Mixtures of 1-Butyl3-methylpyridinium Tetrafluoroborate + Water, + Ethanol, and + Nitromethane. J. Chem. Eng. Data 2007, 52, 2261−2265. (48) Fernández, A.; Torrecilla, J. S.; García, J.; Rodríguez, F. Thermophysical Properties of 1-Ethyl-3-methylimidazolium Ethylsulfate and 1-Butyl-3-methylimidazolium Methylsulfate Ionic Liquds. J. Chem. Eng. Data 2007, 52, 1979−1983. (49) Yamamuro, O.; Minamimoto, Y.; Inamura, Y.; Hayashi, S.; Hamaguchi, H. Heat Capacity and Glass Transition of an Ionic Liquid 1-Butyl-3-methylimidazolium Chloride. Chem. Phys. Lett. 2006, 423, 371−375. (50) Shimizu, Y.; Ohte, Y.; Yamamura, Y.; Saito, K.; Atake, T. Low Temperature Heat Capacity of Room - Temperature Ionic Liquid, 1Hexyl-3-methylimidazolium Bis(trifluoro-methylsulfonyl)imide. J. Phys. Chem. B 2006, 110, 13970−13975. (51) Zhang, Z. H.; Tan, Z. C.; Sun, L. X. Thermodynamic Investigation of Room Temperature Ionic Liquid: The Heat Capacity and Standard Enthalpy of Formation of EMIES. Thermochim. Acta 2006, 447, 141−146. (52) Diedrichs, A.; Gmehling, J. Measurement of Heat Capacities of Ionic Liquids by Differential Scanning Calorimetry. Fluid Phase Equilib. 2006, 244, 68−77. (53) Waliszewski, D.; Stępniak, I.; Piekarski, H.; Lewandowski, A. Heat Capacities of Ionic Liquids and Their Heats of Solution in Molecular Liquids. Thermochim. Acta 2005, 433, 149−152. (54) Nebig, S.; Bolts, R.; Gmehling, J. Measurements of VaporLiquid Equilibria (VLE) and Excess Enthalpies (HE) of Binary Systems with 1-Alkyl-3-methylimidazolium Bis(trifluoro-methylsulfonyl)imide and Prediction of These Properties and γ∞ Using Modified UNIFAC (Dortmund). Fluid Phase Equilib. 2007, 258, 168−178. (55) Paduszyński, K.; Domańska, U. Thermodynamic Modeling of Ionic Liquid Systems: Development and Detailed Overview of Novel Methodology Based on the PC-SAFT. J. Phys. Chem. B 2012, 116, 5002−5018. (56) Nann, A.; Held, C.; Sadowski, G. Liquid − Liquid Equilibria of 1-Butanol/Water/IL Systems. Ind. Eng. Chem. Res. 2013, 52, 18472− 18481. (57) Passos, H.; Khan, I.; Mutelet, F.; Oliveira, M. B.; Carvalho, P. J.; Santos, L. M. N. B. F.; Held, C.; Sadowski, G.; Freire, M. G.; Coutinho, J. A. P. Vapor − Liquid Equilibria of Water + Alkylimidazolium-Based Ionic Liquids: Measurements and Per-

(22) Rebelo, L. P. N.; Najdanovic-Visak, V.; Visak, Z. P.; Nunes da Ponte, M.; Szydłowski, J.; Cerdeiriña, C. A.; Troncoso, J.; Romaní, L.; Esperança, J. M. S. S.; Guedes, H. J. R.; de Sousa, H. C. A Detailed Thermodynamic Analysis of [C4mim][BF4] + Water as a Case Study to Model Ionic Liquid Aqueous Solutions. Green Chem. 2004, 6, 369− 381. (23) Królikowska, M.; Zawadzki, M.; Królikowski, M. Physicochemical and Thermodynamic Study on Aqueous Solutions of Dicyanamide − Based Ionic Liquids. J. Chem. Thermodyn. 2014, 70, 127−137. (24) Ficke, L. E.; Brennecke, J. F. Interactions of Ionic Liquids and Water. J. Phys. Chem. B 2010, 114, 10496−10501. (25) Zhang, Z.-F.; Li, J.-G.; Zhang, Q.-G.; Guan, W.; Yang, J.-Z. Enthalpy of Solution of Amino Acid Ionic Liquid 1-Ethyl-3methylimidazolium Ammonioacetate. J. Chem. Eng. Data 2008, 53, 1196−1198. (26) Fang, D.-W.; Sun, Y.-C.; Wang, Z.-W. Solution Enthalpies of Ionic Liquid 1-Hexyl-3-methylimidazolium Chloride. J. Chem. Eng. Data 2008, 53, 259−261. (27) Ortega, J.; Vreekamp, R.; Marrero, E.; Penco, E. Thermodynamic Properties of 1-Butyl-3-methylpyridinium Tetrafluoroborate and Its Mixtures With Water and Alkanols. J. Chem. Eng. Data 2007, 52, 2269−2276. (28) Constantinescu, D.; Schaber, K.; Agel, F.; Klingele, M. H.; Schubert, T. J. S. Viscosities, Vapor Pressures, and Excess Enthalpies of Choline Lactate Plus Water, Choline Glycolate Plus Water, and Choline Methanesulfonate Plus Water Systems. J. Chem. Eng. Data 2007, 52, 1280−1285. (29) Guan, W.; Yang, J.-Z.; Li, L.; Wang, H.; Zhang, Q.-G. Thermochemical Properties of Aqueous Solution Containing Ionic Liquids 1. The Heat of Reaction Mixed 1-Methyl-3-butylimidazolium Chloride With InCl3. Fluid Phase Equilib. 2006, 239, 161−165. (30) Yang, J.-Z.; Zhang, Z.-H.; Fang, D.-W.; Li, J.-G.; Guan, W.; Tong, J. Studies on Enthalpy of Solution for Ionic Liquid: The System of 1-Methyl-3-ethylimidazolium Tetrafluoroborate (EMIBF4). Fluid Phase Equilib. 2006, 247, 80−83. (31) Archer, D. G.; Widegren, J. A.; Kirklin, D. R.; Magee, J. W. Enthalpy of Solution of 1-Octyl-3-methylimidazolium Tetrafluoroborate in Water and in Aqueous Sodium Fluoride. J. Chem. Eng. Data 2005, 50, 1484−1491. (32) Guan, W.; Wang, H.; Li, L.; Zhang, Q.-G.; Yang, J.-Z. Enthalpy of Solution of the Ionic Liquid BMIBF4 in Water. Thermochim. Acta 2005, 437, 196−197. (33) Katayanagi, H.; Nishikawa, K.; Shimozaki, H.; Miki, K.; Westh, P.; Koga, Y. Mixing Schemes in Ionic Liquid-H2O Systems: A Thermodynamic Study. J. Phys. Chem. B 2004, 108, 19451−19457. (34) Jacquemin, J.; Feder-Kubis, J.; Zorębski, M.; Grzybowska, K.; Chorążewski, M.; Hensel-Bielówka, S.; Zorębski, E.; Paluch, M.; Dzida, M. Structure and Thermal Properties of Salicylate - Based- Protic Ionic Liquids as New Heat Storage Media. COSMO-RS Structure Characterization and Modeling of Heat Capacities. Phys. Chem. Chem. Phys. 2014, 16, 3549−3557. (35) Sattari, M.; Gharagheizi, F.; Ilani-Kashkouli, P.; Mohammadi, A. H.; Ramjugernath, D. Development of a Group Contribution Method for the Estimation of Heat Capacities of Ionic Liquids. J. Therm. Anal. Calorim. 2014, 115, 1863−1882. (36) Gonzalez, E. J.; Gonzalez, B.; Macedo, E. A. Thermophysical Properties of the Pure Ionic Liquid 1-Butyl-1-Methylpyrrolidinium Dicyanamide and Its Binary Mixtures With Alcohols. J. Chem. Eng. Data 2013, 58, 1440−1448. (37) Domańska, U.; Zawadzki, M.; Królikowski, M. Heat Capacity, Excess Molar Volumes and Viscosity Deviation of Binary Systems of N-Octylisoquinolinium Bis{(trifluoromethyl)-sulfonyl}imide Ionic Liquid. Z. Phys. Chem. 2013, 227, 217−238. (38) Królikowska, M.; Paduszyński, K.; Hofman, T.; Antonowicz, J. Heat Capacities and Excess Enthalpies of the (N-Hexylisoquinolinium Thiocyanate Ionic Liquid + Water) Binary Systems. J. Chem. Thermodyn. 2012, 55, 144−150. (39) Ren, J.; Zhao, Z.; Zhang, X. Vapor Pressures, Excess Enthalpies, and Specific Heat Capacities of the Binary Working Pairs Containing I



Article

turbed-Chain Statistical Associating Fluid Theory Modeling. Ind. Eng. Chem. Res. 2013, 53, 3737−3748. (58) Mac Dowel, N.; Llovell, F.; Sun, N.; Hallet, J. P.; George, A.; Hunt, P. A.; Welton, T.; Simmons, B. A.; Vega, L. F. New Experimental Density Data and Soft-SAFT Models of Alkylimidazolium ([CnC1im]+) Chloride (Cl−), Methylsulfate ([MeSO4]−), and Dimethyl-phosphate ([Me2PO4]−) Based Ionic Liquids. J. Phys. Chem. B 2014, 118, 6206−6221. (59) Llovell, F.; Valente, E.; Vilaseca, O.; Vega, L. F. Modeling Complex Associating Mixtures with [Cn-mim][Tf2N] Ionic Liquids: Predictions from the Soft-SAFT Equation. J. Phys. Chem. B 2011, 115, 4387−4398. (60) Martins, M. A. R.; Neves, C. M. S. S.; Kurnia, K. A.; Luis, A.; Santos, L. M. N. B. F.; Freire, M. G.; Pinho, S. P.; Coutinho, J. A. P. Impact of the cation symmetry on the mutual solubilities between water and imidazolium - based ionic liquids. Fluid Phase Equilib. 2014, 375, 161−167. (61) Khan, I.; Kurnia, K. A.; Mutelet, F.; Pinho, S. P.; Coutinho, J. A. P. Probing the Interactions between Ionic Liquids and Water: Experimental and Quantum Chemical Approach. J. Phys. Chem. B 2014, 118, 1848−1860. (62) Królikowska, M.; Lipiński, P.; Maik, D. Density, Viscosity and Phase Equilibria Study of {Ethylsulfate - Based Ionic Liquid + Water} Binary Systems as a Function of Temperature and Composition. Thermochim. Acta 2014, 582, 1−9. (63) Domańska, U.; Łachwa, J. Thermodynamics of Binary Mixtures of N-methyl-2-pyrrolidinone and Ketone. Experimental Results and Modelling of the (Solid + Liquid) Equilibrium and the (Vapour + Liquid) Equilibrium. The Modified UNIFAC (Do) Model Characterization. J. Chem. Thermodyn. 2005, 37, 692−704. (64) Paduszyński, K.; Królikowski, M.; Domańska, U. Excess enthalpies of mixing of piperidinium ionic liquids with short - chain alcohols: measurements and PC - SAFT Modeling. J. Phys. Chem. B 2013, 117, 3884−3891. (65) Reading, M.; Hourston, D. Modulated Temperature Differential Calorimetry; Springer: 2006. (66) Design Institute for Physical Properties, Sponsored by AIChE [2005; 2008; 2009; 2010]. DIPPR Project 801, Full Version. Design Institute for Physical Property Research/AIChE. Online version available at http://knovel.com/web/portal/browse/display?_EXT_ KNOVEL_DISPLAY_bookid=1187&VerticalID=0. (67) Gross, J.; Sadowski, G. Perturbed - Chain SAFT: An Equation of State Based on a Perturbation Theory for Chain Molecules. Ind. Eng. Chem. Res. 2001, 40, 1244−1260. (68) Gross, J.; Sadowski, G. Application of the Perturbed - Chain SAFT Equation of State to Associating Systems. Ind. Eng. Chem. Res. 2002, 41, 5510−5515. (69) Wertheim, M. S. Fluids with Highly Directional Attractive Forces. I. Statistical Thermodynamics. J. Stat. Phys. 1984, 35, 19−34. (70) Wertheim, M. S. Fluids with Highly Directional Attractive Forces. II. Thermodynamic Perturbation Theory and Integral Equations. J. Stat. Phys. 1984, 35, 35−47. (71) Wertheim, M. S. Fluids with Highly Directional Attractive Forces. III. Multiple Attraction Sites. J. Stat. Phys. 1986, 42, 459−476. (72) Wertheim, M. S. Fluids with Highly Directional Attractive Forces. IV. Equilibrium Polymerization. J. Stat. Phys. 1986, 42, 477− 492. (73) Folas, G. K.; Kontogeorgis, G. M. Thermodynamic Models for Industrial Applications: From Classical and Advanced Mixing Rules to Association Theories; John Wiley & Sons: Chichester, U.K., 2010. (74) Wolbach, J.; Sandler, S. Using Molecular Orbital Calculations To Describe the Phase Behavior of Cross-Associating Mixtures. Ind. Eng. Chem. Res. 1998, 37, 2917−2928. (75) Armstrong, J. P.; Hurst, C.; Jones, R. G.; Licence, P.; Lovelock, K. R.; Satterley, C. J.; Villar-Garcia, I. J. Vapourisation of Ionic Liquids. Phys. Chem. Chem. Phys. 2007, 9, 982−990. (76) Tsivintzelis, I.; Grenner, A.; Economou, I. G.; Kontogeorgis, G. M. Evaluation of the Nonrandom Hydrogen Bonding (NRHB) Theory and the Simplified Perturbed - Chain − Statistical Associating

Fluid Theory (sPC-SAFT). 2. Liquid−Liquid Equilibria and Prediction of Monomer Fraction in Hydrogen Bonding Systems. Ind. Eng. Chem. Res. 2008, 47, 5651−5659.

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