Density Of Ionic Liquids Research Articles

A Fluctuation Equation of State for Prediction of High-Pressure Densities of Ionic Liquids

During this work, we demonstrate, for the first time, that the volumetric properties of pure ionic liquids could be truly predicted as a function of temperature from 219 K to 473 K and pressure up to 300 MPa. This has been achieved by using only density and isothermal compressibility data at atmospheric pressure through the Fluctuation Theory-based Tait-like Equation of State (FT-EoS). The experimental density data of 80 different ionic liquids, described in the literature by several research groups as a function of temperature and pressure, was then used to provide comparisons. Excellent predictive capability of FT-EoS was observed with an overall relative absolute average deviation close to 0.14% for the 15,298 data points examined during this work.

Choline chloride based ionic liquids containing nickel chloride: Physicochemical properties and kinetics of Ni(II) electroreduction

The effect of Ni(II) salt content in ethaline (a deep eutectic solvent containing a mixture of ethylene glycol and choline chloride) on density, surface tension, viscosity and conductivity of ionic liquids has been investigated in the temperature range of 25 to 80°C. The introduction of NiCl2·6H2O into ethaline (ca. 0.1–1moldm−3 Ni(II)) causes an increase in the density, surface tension and viscosity of solutions and a decrease in their conductivity. The obtained results are explained in terms of hole theory. Both the electrical conductivity and the viscosity of ionic solutions under consideration are controlled by the availability of suitably sized holes in the liquid. The cyclic voltammetry study performed on nickel electrode shows an irreversible electrochemical behavior of the system Ni(II)/Ni, although the experimental results cannot be interpreted by means of common equations, derived for linear sweep voltammetric responses involving uncomplicated irreversible electrode processes. This may be due to the fact that the solutions do not contain an excess of supporting electrolyte and there is an appreciable migration contribution. In addition, our findings confirm previously developed concept according to that diffusion in ionic liquids disobeys the Stokes–Einstein equation and the transport behavior in ionic liquids cannot be described in terms of “classical” model of diffusion. The activation energy of the charge transfer for the reaction Ni(II) + 2e− → Ni in ethaline has been determined at constant values of electrode potential (the so-called formal activation energy).

High temperatures and high pressures density measurements of 1-ethyl-3-methylimidazolium methanesulfonate and Tait-type equation of state

Density of ionic liquid (IL) 1-ethyl-3-methylimidazolium methanesulfonate (short name [EMIM][MeSO3]) at high temperatures and high pressures were measured. The measurements have been made at pressures up to 60MPa for 10 isotherms between 273 and 413K using an Anton Paar DMA HPM vibration tube densimeter (VTD). The measuring system was calibrated using various standard fluids (double- distilled water, aqueous NaCl solutions, methanol, ethanol, toluene and acetone) with well-known density data. The combined expanded uncertainty of the density (ρ), pressure (P), and temperature (T) measurements at the 95% confidence level with a coverage factor of k=2 is estimated to be 0.01 to 0.08% depending on temperature and pressure ranges, 0.1%, and 15mK, respectively. We have critically assessed all of the reported density data at atmospheric pressure together with the present results for their internal consistence to carefully select primary data to fit reference correlation, ρ0(T). This correlation ρ0(T) together with the present high-pressure density measurements (ρ, P, T) were used to develop two-parametric (c and B) and theoretically based Tait- type equation of state. The theoretical interpretation and physical meaning of the Tait's parameters (c and B) and their temperature behavior was discussed.

Correlating ionic liquids density over wide range of temperature and pressure by volume shift concept

The main purpose of this paper is the use of the conventional Peng–Robinson equation of state (PR EoS) and the concept of volume shift to correlate and predict pure ionic liquids (ILs) density in a wide range of temperature and pressure. A total number of 67 pure ILs (5020 data points) including different cations and anions were used in this study over temperature and pressure range of 273.15–473.15K and 0.1–205MPa. At first, the volume shift parameter (c) of 67 ILs in any temperature and pressure were optimized using genetic algorithm. An equation similar to Gardas and Coutinho (R. L. Gardas, J. A. P. Coutinho, Fluid Phase Equilibr. 263 (2008) 26–32) was used for c parameter and finally a generalized correlation was proposed for c as a function of temperature, pressure and critical molar volume. This equation was also used in predicting densities of eight new ILs not included in correlation section and it was able to improve the PR EoS prediction and reducing the error with respect to experimental data. Considering the importance of density in engineering, using this simple equation with the VTPR improves ILs density prediction and calculation, saves time and increases the accuracy engineering design. The average absolute percent deviation (AAPD) of the volume translated PR (VTPR) EoS and the conventional PR EoS were equal to 2.19% and 12.98%, respectively.

A reliable radial basis function neural network model (RBF-NN) for the prediction of densities of ionic liquids

Abstract Density of liquids is an important physical property which clear knowledge of its value is essential in various scientific and engineering applications such as design of equipment, liquid metering calculations and many other applications. Hence, developing accurate and reliable predictive tools for prediction of this property seems to be of great importance. In this communication, a model was developed based on radial basis function neural network (RBF-NN) for estimation of density values of 146 ionic liquids at various temperatures. The outputs of the study reveal that the new model is capable to predict density data with an acceptable accuracy. The reliability and precision of the model was validated by using various statistical and graphical approaches. Results of the developed model were put into comparison with literature correlations and it was observed that the model effectively outperforms other correlations and exhibit higher accuracy and reliability.

The Viscosity and Density of Ionic Liquid + Tetraglyme Mixtures and the Effect of Tetraglyme on CO2 Solubility

We show that the addition of tetraglyme (TG), which is a low viscosity liquid with relatively low vapor pressure, is effective in reducing the viscosity of ionic liquids (ILs). In particular, we measure the viscosities of mixtures of 18 ionic liquids with tetraglyme at temperatures between 278.15 and 323.15 K, with a focus on mixtures that are primarily ionic liquid. Thirteen of the ionic liquids contain aprotic heterocyclic anions (AHA ILs) paired with tetra-alkylphosphonium and imidazolium cations, which we have developed for cofluid vapor compression refrigeration and postcombustion CO2 capture applications. Three bis(trifluoromethylsulfonyl)amide ([Tf2N]−) ionic liquids are included for comparison, as well as trihexyltetradecylphosphonium acetate and trihexyltetradecylphosphonium dicyanamide ([P66614][acetate] and [P66614][DCA]). In addition, we present the densities of trihexyltetradecylphosphonium 1,2,3-triazolide ([P66614][3-Triz]) + tetraglyme mixtures at temperatures between 283.15 and 353.15 K. Finally, we show that the solubility of CO2 in mixtures of [P66614][3-Triz] + 30 mol % tetraglyme and trihexyltetradecylphosphonium 1,2,4-triazolide ([P66614][4-Triz]) + 30 mol % tetraglyme at 313.15, 333.5, and 353.6 K and pressures to 34 bar can be represented reasonably well by a mole fraction weighted sum of the solubilities (on a mole ratio basis) in the two pure components.

镁基类离子液体制备及物化性质的测定

以氯化胆碱和六水氯化镁为原料，采用自组装反应直接合成镁基类离子液体。对合成的类离子液体的粘度、电导率、密度和组成的变化关系进行了分析。结果表明合成的温度和组成是影响类离子液体物化性能的关键因素。随着温度和组成的变化，镁基类离子液体的粘度、电导率、密度均发生显著的变化。 With choline chloride magnesium chloride hydrate as raw material, magnesium ion liquid was synthesized by self-assembly reaction. The viscosity, conductivity, density and composition of the ionic liquids were analyzed. The results show that the temperature and composition were the key factors affecting the physicochemical properties of the ionic liquids. With the change of temperature and composition, the viscosity, conductivity and density of magnesium ionic liquids were changed significantly.

Representation of phase behavior of ionic liquids and their mixtures using various forms of cubic-two-state equation of state

In this work, in addition of Soave-Redlich-Kwong (SRK) equation of state, two other alternative cubic models such as Peng- Robinson (PR) and Cubic Square Well (CSW) EoSs are combined with the Two-State Association Model (TSAM) and the new forms of the Cubic-Two-State equation of state (CTS EoS) as PR-TS and CSW-TS are presented. In the beginning, the present models are used to correlate the saturated vapor pressure and liquid density of pure water, alcohols and phenol. The models are also employed to predict vapor molar volume and second virial coefficients of pure compounds to explore the predictability of the different type of the CTS models. Also, the liquid density of different pure ionic liquids (ILs) at various temperatures from 298.15 K up to 500 K and pressure from 0.1 MPa up to 59.59 MPa is correlated and the parameters of the CTS models are obtained. Following successful application of the models for the pure components, using one temperature independent binary interaction parameter, the SRK-TS and PR-TS models are applied to predict the vapor-liquid equilibrium of the several binary mixtures consists of IL with non-association and association components at various temperatures from 298.15 K up to 363.15 K and pressure from 0.09 kPa up to 216 kPa. The results of the SRK-TS and PR-TS models for pure and binary systems containing ILs are in very good agreement with experiments and also are compared with various equations of states that show better results. In overall for the systems that are presented in this work, the PR-TS model shows slightly better results with respect to the SRK-TS model specially in prediction, and PR-TS and SRK-TS models present superiority with respect to the CSW-TS EoS.

Thermodynamic modeling of solubility of hydrogen sulfide in ionic liquids using Peng Robinson-Two State equation of state

In this work, a simple association equations of state, namely Peng Robinson-Two state (PR-TS) association model is applied to model the PVT behavior of pure ionic liquids and solubility of H2S in 12 various imidazolium-based ionic liquids. This equation of state consists of two terms, the Peng-Robinson (PR) equation of state as cubic term for non-specific energy contribution and two-state association model (TSAM) for association energy contribution. First, to obtain the parameters of the PR-TS EoS for pure components, the experimental liquid density of different pure ionic liquids at various temperatures and pressures are correlated and the percent absolute average deviation between the calculated and experimental densities of ionic liquids is about 0.24%. For pure H2S two association schemes are considered as in the presence or not of association behavior. Then, the parameters of the model for these two schemes are correlated by simultaneously optimization of vapor pressure and liquid density data. Following successful application of the model for the pure components the PR-TS EoS is applied to predict the vapor-liquid equilibrium (VLE) of the several H2S + IL binary mixtures with this assumption that in binary mixtures present cross-association or self-association interaction. For binary systems in first approach only one interaction parameter is used and in second approach two binary interaction parameters are applied. The results of the VLE calculation of the H2S + IL systems show that the best accuracy with AAD = 3.40% is obtained when H2S is considered as non-association component and is used two binary interaction parameters for modeling the binary systems. In overall, the results of the present model for pure and binary systems comprise H2S and ILs are in very good agreement with experiments.

A GEP based model for prediction of densities of ionic liquids

Abstract One of the most important properties of ionic liquids (ILs) is their densities. Accurate knowledge of this property is required in engineering and scientific purposes including equipment design, liquid metering calculations, and other applications. As a result, it is important to develop accurate and effective models for prediction of this property. The present work aims to develop a model based on Gene Expression Programming (GEP) technique for prediction of experimental density values of 146 different ionic liquids at different temperatures. A databank containing 602 data gathered from the literature was utilized to develop the model. The input parameters of the model are temperature, molecular weight of IL, normal boiling point temperature of IL, critical pressure of IL, critical volume of IL, and acentric factor of IL. The outcomes of this work indicate that the developed model is capable of estimating target density data with an acceptable accuracy. The effectiveness and accuracy of the model were checked by utilizing different statistical and graphical techniques. Moreover, results of the proposed model are compared with predictions of literature correlations and it is shown that the GEP model is effectively superior to other correlations and exhibits higher accuracy and reliability.

The implementation of ion-based ePC-SAFT EOS for calculation of the mean activity coefficient of single and mixed electrolyte solutions

Following our previous work (Journal of Molecular Liquids 221 (2016) 904–913), the modified perturbed chain statistical associating fluid theory (ePC-SAFT) incorporated with Debye-Huckel term has been applied to calculate some thermodynamic properties of single and mixed electrolyte solutions. The applicability of this model has been investigated by calculation of the mean ionic activity and osmotic coefficients of electrolyte solutions as well as the water activity of regarded systems at different temperatures. Firstly, water-ion hydration has been taken into account independently by two individual strategies, i.e. ions can be considered as non-associating and associating compounds distinctly. Afterwards, a new set of ion parameters containing 31 common ions has been estimated using the experimental mean ionic activity coefficients and liquid densities of 78 binary electrolyte solutions in both strategies. The optimized parameters which have been utilized for prediction of single-salt aqueous electrolyte solutions MIACs up to 373.15 K are global and transferable to different salts. Eventually, it can be observed that not only the density of aqueous electrolyte solutions, but also MIACs, osmotic coefficients and water activity of single and mixed salt solutions are satisfactorily calculated by considering ions as association compounds over a wide range of temperature and salt concentration.

ANFIS modeling of ionic liquids densities

The aim of this study is to implement an accurate model for prediction of density of ionic liquids at various temperatures based on an extensive data base gathered from literature published works. The data base includes 602 density data points of 146 ionic liquids at various temperatures. The developed model is based on adaptive neuro-fuzzy inference system (ANFIS) algorithms. The predictions of the developed model were analyzed by various methods including both statistical and graphical approaches. The predictions of the developed model were compared with outcomes of literature correlations for predictions of density of pure liquids. Results show that the developed model accurately predicts the experimental data with an overall R2 and AARD% values of 0.985 and 0.657%, respectively. Moreover, the developed model effectively outperforms literature correlations and presents more accurate and reliable predictions.

An accurate CSA-LSSVM model for estimation of densities of ionic liquids

This study highlights the application of a model based on least square support vector machine (LSSVM) for estimation of densities of ionic liquids (ILs). The tuning parameters of the developed model were determined by an optimization algorithm namely coupled simulated annealing (CSA). A set of 602 data points of density for 146 ionic liquids was utilized to implement the model. Statistical and graphical methods were utilized to evaluate the precision and effectiveness of the developed model for prediction of experimental data. The results were also compared with results of literature correlations for prediction of density of pure liquids. Results show that the model is accurate and effective for prediction of experimental density data. The model exhibits an overall R2 and AARD% values of 0.9808 and 0.89%, respectively. Moreover, comparison between results of literature correlations and the developed model show the reliability and superiority of the proposed CSA-LSSVM model.

Estimation of the Densities of Ionic Liquids Using a Group Contribution Method

A simple and general atomic group contribution method is developed for the prediction of liquid densities of ionic liquids as a function of temperature and pressure. Available literature data are used as a comprehensive database, consisting of 25 850 data points for a vast variety of ionic liquid families, and within wide ranges of pressures (0.10–300 MPa) and temperatures (217.58–473.15 K). In developing the group contribution model, the idea was to propose a simple equational form, with straightforward groups which will be easy to use, yet be general and predictive for a vast range of ionic liquids at the same time. To do this, as functional groups, we have chosen atoms and a few small and simple groups. This feature makes the model rather capable and global for a wide range of ionic liquids. Despite the generality and simplicity of the model, and by considering that the only necessary information required to use this method is the chemical structure of the ionic liquid, a good accuracy (AARD% of 0.95%)...

Density, refractive index and kinematic viscosity of MIPK, MEK and phosphonium-based ionic liquids and the excess and deviation properties of their binary systems

The density, refractive index, and kinematic viscosity were measured for extraction solvents for molybdenum: methyl ethyl ketone (MEK), methyl isopropyl ketone (MIPK), trihexyl tetradecyl phosphonium chloride ([P666,14] [Cl]), trihexyl tetradecyl phosphonium dicyanamide ([P666,14][DCA]) and trihexyl tetradecyl phosphonium bis (2,2,4- trimethyl pentyl) phosphinate ([P666,14][TMPP]) at atmospheric pressure for a temperature range of 288.15-318.15 K. The experimental data were correlated using the Daubert and Danner equation, a linear equation and the Goletz and Tassion equation. In addition, the excess molar volumes (VE) and the deviations in molar refractivity (ΔR) at 298.15 K were reported for the following binary systems: {MEK+[P666,14][Cl]}, {MEK+[P666,14][DCA]}, {MEK+[P666,14][TMPP]}, {MIPK+[P666,14][Cl]}, {MIPK+[P666,14][DCA]} and {MIPK+[P666,14][TMPP]}. The determined VE and ΔR values were correlated with the Redlich-Kister equation. The binary density and refractive index data at 298.15 K were also predicted using several mixing rules, and these results were then compared with the experimental data.

Application of Ionic Liquid Electrolyte to Lithium Ion Capacitor Based on Electrodes with Porous Three-Dimensional Current Collector

A lithium ion capacitor (LIC) is a new storage device which combines an electric double-layer capacitor (EDLC) with a lithium ion battery (LIB). Namely, LIC consists of an activated carbon as positive electrode and lithium-ion-intercalating carbon material such as hard carbon as negative electrode. LIC also contains functionalities derived from both EDLC and LIB. During charge and discharge of LIC, ion adsorption/desorption occurs on the surface of the positive electrode, while lithium ion intercalation/de-intercalation occurs at the negative electrode. Although LIC features an excellent power density like EDLC, the energy density of LIC is lower than that of LIB. Therefore, improvement of energy density is required for LIC. In the present study, to achieve high energy density of LIC, porous 3-dimensinal (3D) current collector is applied to LIC electrodes. It is possible to increase the packing density of active material and make a LIC cell lighter. It is, however, expected that diffusion of carriers is limited with conventional organic electrolytes because electrodes using porous 3D current collector become massive; the typical thickness is ca. 1 mm. As a result, LIC using porous 3D current collector may deliver limited power. Thus, ionic liquids which have high carrier density would be useful as electrolyte of LIC to maintain power. The purpose of this study is applying an ionic liquid electrolyte to LICs with porous 3D current collector and investigating the basic operating characteristics.We assembled a three-electrode cell. A positive electrode using aluminum porous 3D current collector was made from activated carbon (AC, 87 wt.%), acetylene black (AB, 3 wt.%) and polyvinylidene di-fruoride (PVdF, 10 wt.%). A negative electrode using copper porous 3D current collector was made from hard carbon (HC, 87 wt.%), AB (8 wt.%) and PVdF (5 wt.%). A lithium foil was used as a counter electrode and reference electrode. The electrolyte was 1.5 mol dm−3 LiFSI/EMImFSI. The cell was galvanostatically charged and discharged for 3000 cycles at 1.0 C-rate in a voltage range of 2.0 – 3.8 V after a pre-doping process under predetermined conditions. We also evaluated rate performances of LIC cells with various electrolytes by rapid charging and discharging test. 1.5 mol dm−3 LiFSI/EMImFSI was used as standard ionic liquid electrolyte. 1.0 mol dm−3 LiPF6 / EC : DMC = 1 : 1 (v/v) and 1.0 mol dm−3 LiBF4 / EC : DMC = 1 : 1 (v/v) were used as organic electrolytes for comparison. C-rates for the power performance test were varied from 0.1 C to 30 C every 5 cycles after 100 pre-cycles.Fig. 1 shows potential profiles of positive and negative electrodes during charge and discharge at 2, 1000, 3000 cycles. It turns out that the LIC cell containing ionic liquid electrolytes is possible to charge and discharge reversibly as well as stably. Even though it was long-term cycling such as 3000 cycles, its capacity has not significantly decreased. Therefore, long-term cycle stability is high. Fig. 2 compares rete performances with the ionic liquid electrolyte and two organic electrolytes. Although ionic liquids have high viscosity [1], it is shown that FSI-based ionic liquid electrolyte has high rete performances comparable to a LiPF6-based organic electrolyte. This may be ascribed to high carrier density of ionic liquids. Rate performances of the FSI-based ionic liquid electrolyte and LiPF6-based organic electrolyte are superior to that of the LiBF4-based organic electrolyte. This is attributed to lower ionic conductivity of LiBF4. These results suggest that applying the ionic liquid electrolyte to a LIC electrode with porous 3D current collector is promising. FSI-based ionic liquid electrolytes may replace conventional organic electrolytes as electrolyte of LIC because of their resulting high cycle stability and high energy density without power loss.

Effect of Oxygenation on Carbon Dioxide Absorption and Thermophysical Properties of Ionic Liquids: Experiments and Modeling Using Electrolyte PC-SAFT

The thermophysical properties (decomposition temperature, glass transition temperature, density, and viscosity) of imidazolium-based ionic liquids (ILs) paired with the tricyanomethanide ([TCM]−) anion and the bis(trifluoromethylsulfonyl)imide ([Tf2N]−) anion were studied within a wide temperature range. The effect of the ether functional group (in [Tf2N]− and [TCM]− ILs) and hydroxyl functional group (in [Tf2N]− IL) incorporated in the cation’s alkyl chain on the thermophysical behavior and carbon dioxide (CO2) solubility was evaluated by comparing their behavior to the corresponding nonfunctionalized ILs. The thermal stability was enhanced by the inclusion of hydroxyl functionalization in the cation’s alkyl chain while ether functionalization had no major effect on the thermal stability. The ether groups (one or two) resulted in an increase in the density and a decrease in the viscosity of all ILs. The hydroxyl group resulted in an increase in both properties. The CO2 solubilities were not affected by the presence of the ether groups, while the hydroxyl group led to a significant decrease in the solubility. Additionally, the electrolyte perturbed-chain statistical associated fluid theory (ePC-SAFT) equation of state was used to calculate the CO2 solubility in the ILs and the Henry’s law constant. The model showed great predictive ability. The Henry’s constants were applied to calculate the partial molar thermodynamic properties of solvation.

Density prediction of pyridinium, imidazolium, pyrrolidinium, ammonium, and phosphonium-based ionic liquids using an equation of state

A group contribution equation of state (EOS) has already been developed to calculate the density of imidazolium-based ionic liquids (ILs) with good accuracy. IL was divided into several groups, i.e. cation head, anion, and alkyls. In order to further prove the widely applicability of the model and the group segmentation method for IL, the densities of 1-alkyl-3-methylimidazolium salts containing metal of group III and a large number of pyridinium, pyrrolidinium, ammonium, and phosphonium-based pure ILs were correlated/predicted in this work. First, a total of 222 data points of density for 27 pure ILs, were regressed to obtain the new soft-core diameter and dispersive energy parameters. Then, 908 density data points of 42 pure ILs from 278.15 to 393.15 K and up to 65.01 MPa were predicted on the basis of the obtained parameters. The results indicated that the EOS could well capture the effects of temperature, pressure and alkyl types on density. Finally, the EOS was further evaluated to predict the density data for binary IL mixtures without introducing any new parameters, and testified the extensive applicability of the EOS with average relative deviation of 0.70%.

Phase Transitions, Decomposition Temperatures, Viscosities, and Densities of Phosphonium, Ammonium, and Imidazolium Ionic Liquids with Aprotic Heterocyclic Anions

Ionic liquids (ILs) with aprotic heterocyclic anions (AHAs) have been developed primarily for CO2 capture applications. However, they have also been considered for cofluid CO2/IL vapor compression refrigeration cycles and for various electrochemical applications. In all of these cases, reducing the viscosity of the IL is of primary importance. Therefore, the focus of this work is tuning the cation to produce AHA ILs with both low viscosities and low melting points. Toward this goal we have synthesized 40 AHA ILs paired with phosphonium, ammonium and imidazolium cations, as well as a number of ILs with the bis(trifluoromethylsulfonyl)imide anion to use for comparison. The azolide anions investigated were 2-cyanopyrrolide, 4-nitropyrazolide, various substituted imidazolides, 1,2,3-triazolide, and tetrazolide. Melting points, glass transition temperatures, and decomposition temperatures were measured for all ILs. Viscosities and densities were measured from 278.15 to 343.15 K and 283.15 to 353.15 K, respecti...

Density, viscosity, refraction index and excess properties of binary mixtures of 1-(1-methypiperidinium-1-yl) pentane-(1-pyridinium) bis(trifluoromethane) sulfonamide with acetonitrile at T=(293.15 to 323.15) K

The density, viscosity, and refractive index of a pure asymmetrical dicationic ionic liquid, 1-(1-methypiperidinium-1-yl) pentane-(1-pyridinium) bis(trifluoromethane)sulfonamide, and its binary mixtures with acetonitrile were investigated at temperatures from 293.15 K to 323.15 K over the entire range of composition at ambient pressure. From the experimental data, the excess molar volumes, dynamic viscosity deviations, and refractive index deviations were, respectively,calculated and correlated with Redlich-Kister-type polynomials. The temperature dependence of viscosity for pure ionic liquid was described by modified Vogel–Tammann-Fulcher (VTF) equation. The enthalpy and entropy of activation for viscous flow were obtained. The values of molar refraction and polarizability indicated that the dominant interactions between ionic liquids and acetonitrile were dipole-dipole molecular interactions. These thermodynamic properties were discussed in terms of nature of molecular interactions between the ionic liquid and acetonitrile.