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In this study, the deep eutectic solvent of choline chloride/urea, also known as Reline, was synthesized. Mixtures of Reline with ethanol were prepared covering the entire concentration range, and their densities were determined experimentally. Together with pure Reline and pure ethanol, this made a total of eleven systems, whose densities were measured over the temperature range of 293.15–333.15 K at pressure of 100 kPa. The volumetric properties of interest in the calculation of other derivative thermodynamic properties were determined for all of the investigated mixtures and temperatures. This included the correlation of density to temperature, as well as the excess molar volumes, partial molar volumes, partial molar volumes at infinite dilution, excess partial molar volumes, excess partial molar volumes at infinite dilution, and isobaric volume expansions. The excess molar volumes had negative values at all concentrations and temperatures. This led us to propose a possible molecular arrangement of the hydrogen bond network, placing Reline mainly in central positions, with the preference to be surrounded by ethanol molecules.

Deep eutectic solvents (DESs) make up a most-recent category of ‘green’ solvents with a potentially promising future. Insignificant vapor pressure, biodegradability, low cost, task-specific engineering, and high absorption for gases such as CO2 are the most important characteristics of most DESs. To apply DESs in various industries, knowledge of their physical properties is vital. Since the viscosity of a DES is a strong function of temperature, as well as the ratio of the hydrogen bond donating and accepting components, to estimate the viscosity behavior, a model based on sound theory is proposed in this study, i.e., the free volume theory. Since DESs are strongly associating components, this theory is enriched by using associating equations of state, namely CPA and PC-SAFT. In this study, a large density and viscosity databank of 27 DESs of different nature, also with varying molar ratios of the hydrogen bond donor and acceptor, were used to propose the model. In this way, a global model is presented for the first time to estimate the viscosities of DESs. The pseudo-component approach, with a 2B association scheme, was considered for the DESs. Both the CPA and the PC-SAFT EoSs, coupled with the free volume theory, showed reliable results, with average AARD% values in viscosity for all of the investigated DESs equal to 2.7% and 2.7%, respectively. Furthermore, both models reliably showed the trend of nearly logarithmic increase in DES viscosity with decreasing temperature. Also, both models accurately estimated the viscosity behavior of the DESs by not only changing the molecular nature of the hydrogen bond donor with a fixed hydrogen bond acceptor, but also at all of the various molar ratios investigated.

In this study, the aqueous mixture viscosities of two phenolic DESs, consisting of (1 ChCl: 3 phenol) and (1 ChCl: 4 phenol), were measured at atmospheric pressure over the temperature range of 293.15 - 333.15 K. According to the measured data, the values of viscosity deviations for the investigated aqueous systems were calculated to indicate deviating viscosity behavior with respect to ideality. Both aqueous systems showed negative viscosity deviations over the entire composition range and at all of the investigated temperatures. The Redlich-Kister model was applied to estimate the viscosity deviations of both aqueous systems at different compositions and temperatures, while the viscosity behavior, itself, was modeled by different literature models, consisting of the Grunberg-Nissan, Jouyban-Acree, McAllister, Preferential Solvation, and an Arrhenius-like viscosity model. All of the models presented satisfactory agreement, however the Preferential Solvation and the Jouyban-Acree models succeeded to achieve more reliable results as compared to the others. In addition to the mixture viscosity estimation models, the Jones-Dole viscosity model was applied to both of the aqueous systems to suggest the interactions in the mixture. By calculating and analyzing the values of the B-coefficients of this model, possibly stronger interactions among the DESs and water molecules in the mixture were suggested, as compared to the self-species interactions.

A group contribution procedure, on the basis of SAFT-γ equation, is extended to cover new families of imidazolium-based ionic liquids (ILs), with either the [MeSO3], [MeSO4], [EtSO4] or [CF3SO3] anions. The IL groups of the SAFT-γ equation were fit to IL density data at temperatures from 293.15 to 393.15 K. Pressures varied up to 60 MPa. The groups corresponding to the CO2+IL systems were optimized by the solubility data of CO2 in the ILs. The binary system data covered temperatures from 273.15 to 413.15 K, with pressures going up 27 MPa. In addition to the accuracy of estimations, the strength of SAFT-γ in predictions was investigated by estimating both the density of ILs, and the bubble-point pressures for some mixtures of CO2+ILs which were not considered in the fitting process. The average absolute relative deviations in density and bubble pressure predictions did not exceed 2.78% and 4.97%, respectively.

Deep eutectic solvents have aroused a great level of interest in recent years. In this regard, a simple model is presented for the calculation of viscosities of a wide range of deep eutectic solvents. Based on a databank covering 156 deep eutectic solvents of different natures, a straightforward, simple, accurate, and global correlation is proposed. This model, which covers wide ranges of temperatures, requires the critical pressure, critical temperature, and one reference viscosity data as its input parameters. Since the model has one set of global constants, it can be used for any DES. Apart from this correlation, a second approach was also taken in this study, which was to obtain the constants of the Vogel-Fulcher-Tamman (VFT) model for all of the investigated DESs. With this approach, the constants are individually fit to each DES, therefore, no physical properties are required as input. The average absolute relative deviation errors of 10.4% and 1.7% for the proposed model and the VFT model, respectively, are compared to literature models. The results indicate that the proposed correlation, in addition to its acceptable accuracy and simplicity, is a general model for the estimation of the viscosities of different-natured deep eutectic solvents.

Nitrogen and oxygen are the main components of air. Liquid nitrogen is an alternative to fossil fuels. However, little attention has been paid to this energy resource. Liquid oxygen is not a fuel in itself, however, it can be used as an oxidizer to run vehicles. In this respect, gas hydrate technology can be of interest, as applicable media for nitrogen/oxygen transport or nitrogen/oxygen separation. Both nitrogen and oxygen have the tendency to form hydrates, especially at high pressures, with double occupancy of the large cavities of structure sII. Thermodynamic hydrate promoters (THPs) can be used to facilitate the formation of nitrogen or oxygen hydrates at more moderate equilibrium conditions. For this purpose, CCl4 can be a potential candidate. In this contribution, hydrate equilibrium conditions for binary mixtures of nitrogen + CCl4 (50 data points) and oxygen + CCl4 (41 data points) were experimentally measured. This was done using three different experimental equipment, namely: a tensimeter, the Cailletet apparatus, and a high-pressure autoclave. A thermodynamic model, according to the van der Waals-Platteeuw (vdW-P) solid solution theory, was then employed to predict the hydrate equilibrium temperatures of the aforementioned mixtures. The fugacities of the components in the mixtures were calculated through the Peng-Robinson (PR) EoS and the classical van der Waals mixing rules. The Kihara potential model was applied to represent the guest-host interactions. The results reveal that the model has the ability to predict the hydrate equilibrium temperatures with the average absolute deviation (AAD) of 0.32 K. The fractional occupancy calculations indicate that the CCl4 molecules mostly occupy the large cages and do not enter the small cages of sII hydrates because of their size, while nitrogen and oxygen have small contributions in the filling of the large cages of sII.

In this work, the equilibrium conditions of xenon hydrates have been measured within wide pressure and temperature ranges. Various experimental equipment have been used for this purpose, namely the tensimeter, the Cailletet apparatus, and the high-pressure autoclave. A number of three-phase equilibrium data points were measured for liquid water-hydrate-vapor (Lw-H-V) and the ice-hydrate-vapor (I-H-V). It was concluded that there is a good consistency between the experimental data points measured in this work and those obtained by the other groups in the literature. A modified van der Waals-Platteeuw (vdW-P) model was used to predict the xenon hydrate stability conditions. The Kihara spherical-core potential function was used to represent the intermolecular forces between the water molecules and the xenon molecules in the cavities. The fugacity of xenon in the vapor/gas phase was computed using the Peng-Robinson (PR) EoS. The solubility of xenon in the liquid phase was calculated through the Krichevsky-Kasarnovsky equation. The investigated model had the ability to predict the xenon hydrate stability conditions with good accuracy within wide ranges of pressures and temperatures, resulting in an average absolute deviation (AAD) of about 0.61 K for (Lw-H-V) and 0.42 K for (I-H-V) equilibrium temperatures.

The group contribution equation of state (GC-EoS) is extended to model gas solubilities in the homologous 1-alkyl-3-methylimidazolium bis(trifluoromethyl-sulfonyl) imide family. The gases considered in this work are CO2, CO, H2, CH4, and C2H6. The model parameters were estimated on the basis of 1400 experimental data points in the temperature range of 278-460 K and pressures up to 160 bars. A correlation is also presented to calculate the critical diameter, a characteristic parameter of the GC-EoS repulsive term, as a function of the ionic liquid molar volume. Density data is most often available for ionic liquids; hence, the correlation provides a predictive method for ionic liquids not included in the parameterization process. The new parameters were then used to predict the phase behavior of binary mixtures containing different solutes (including C3H8, C4H10, and C6H14) and ionic liquids with different chain lengths than those used in the parameterization process. Fil: Pereda, Selva. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: Raeissi, Sona. Shiraz University; Irán Fil: Andreatta, Alfonsina Ester. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Bahia Blanca. Planta Piloto de Ingeniería Química (I). Grupo Vinculado al Plapiqui - Investigación y Desarrollo en Tecnología Química; Argentina Fil: Bottini, Susana Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Planta Piloto de Ingeniería Química. Universidad Nacional del Sur. Planta Piloto de Ingeniería Química; Argentina Fil: Kroon, Maaike. Eindhoven University of Technologie; Alemania. Technische Universiteit Eindhoven; Alemania Fil: Peters, Cor J.. Technische Universiteit Eindhoven; Alemania. Eindhoven University of Technology; Alemania. The Petroleum Institute. Chemical Engineering Department - Abu Dhabi; Emiratos Arabes Unidos

The heat capacities of pure ionic liquids (ILs) are among the thermophysical properties that are required for certain engineering calculations and designs. In this study, a simple correlation is presented for the prediction of the heat capacities of pure ionic liquids. This correlation is a temperature-dependent relation that uses temperature, molecular weight and the number of atoms (such as carbon, hydrogen, oxygen, nitrogen, etc.) in the structure of the IL as input parameters. A dataset of approximately 128 different ILs, consisting of 4822 data points, was used to develop and validate this general correlation, covering a temperature range from 190 to 663 K. Nearly three-quarters of the data were used for optimization and a quarter for validation. The resulting correlation gives good estimations for heat capacities, while having a number of advantages over previous literatures methods. These advantages include (a) being very simple; (b) not requiring any experimental data as input parameters; (c) being more global than previous literature models by having been constructed over a larger databank of ionic liquids; (d) being accurate. The average absolute relative deviation (AARD%) was calculated to be 5.8% for the optimization dataset, and 5.6% for the validation dataset. This is smaller than what is obtained for the literature atomic-contribution methods proposed by Farahani et al. and Sattari et al., with AARD% values of 14.2% and 6.6%, respectively, based on the validation dataset of this study.

In this study, a volume-translated version of the Peng–Robinson equation of state (PR EoS) is developed for ionic liquid + polar solvent mixtures to estimate molar volumes within a range of compositions and temperatures. The ionic liquids investigated consisted of various combinations of either the 2-hydroxyethylammonium or the alkyl-methylimidazolium cation with various alkyl chain lengths, with the anions methyl-sulfate, ethyl-sulfate, hydrogen-sulfate, dicyanamide, acetate, bis(trifluoromethylsulfonyl)imide, and tetrafluoroborate. The polar solvents consisted of water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, acetone, nitromethane and dichloromethane. The volume shift parameter, c, was first optimized for all of the systems investigated at each composition and temperature. Based on the values obtained, it was observed that temperature-dependency is negligible. Therefore, a generalized equation was presented for the c parameter as a function of the molar composition of the polar solvent and the molecular weight of the ionic liquid. This relation, which contains a combination of exponential, logarithmic and polynomial terms, was able to improve the predictions of the PR EoS and reduce the errors with respect to experimental data. The average errors of the conventional PR EoS and the volume-translated PR EoS (both without using any binary interaction parameters) were equal to 14.92% and 5.91%, respectively. The added advantage of using this correlation is that it omits the need to optimize any binary interaction coefficients in such highly nonideal systems, making it a very simple and practical engineering tool for the industries, while at the same time increasing predictive accuracy.

The goal of this study was to propose, a general, yet simple and accurate model for the estimation of the standard molar chemical exergies of various organic compounds, often used in the industries. With this goal in mind, for the first time in literature, the atomic contribution approach was considered, and the feasibility of adopting such a simple method to calculate chemical exergies was investigated. A large data bank, consisting of 4129 organic compounds from wide ranges of families, was gathered from the literature, and divided into training and test datasets. Upon investigating various functionalities, and optimizing using the training databank, two atomic contribution models were proposed to calculate the standard enthalpy and entropy of formation, from which, the standard molar chemical exergy of a compound is calculated. The AARD% value for estimating the standard molar chemical exergy of the entire database, consisting of both the training and testing datasets, was 0.64%, which shows not only the feasibility of applying the atomic contribution approach for the calculation of this property, but also high accuracy as compared to more tedious literature models. Since the proposed models require knowledge of only the chemical formula and the normal boiling point of the desired compound, it is indeed in line with our purpose of simplicity and generality, and can easily be incorporated into computer codes. Considering that it is also global and quite accurate, this model even has great potential to be used in energy and chemical-related software.

Ionic Liquids (ILs) are designer solvents with very unique properties, resulting in the exponential growth of publications in the field. Speed of sound can be considered as one of the important thermodynamic properties of compounds, since many other thermophysical properties can be determined using the speed of sound, including density, isentropic compressibility, isothermal compressibility, thermal conductivity, heat capacity, Joule-Thomson coefficient, and bulk modulus. Since ILs are designer solvents, much of their properties are unknown, hence, knowledge of their speeds of sound can be quite valuable. Two new straightforward models, with totally different approaches and input parameters, are proposed to estimate the speed of sound in ILs: an atomic contribution model, which only considers the atoms as building blocks to create the molecule and estimate its speed of sound; and a novel correlation. The atomic contribution model is the first which requires knowledge of only the chemical formula of the IL, making it needless of, not only any physical properties, but also the molecular structure which group contribution methods do require. This is considerable progress, as it will cover the majority of future ILs, which have not even been synthesized, and it does not have the ambiguities and difficulties of conventional group contribution (GC) methods for such complex structures. The further notable progress is its easy incorporation into computer programs, which is a serious setback with GC models. However, while being very straightforward and easy-to-use, it is more global than literature models. In addition to the atomic contribution method, a novel empirical correlation is proposed, with a new perspective. Both proposed models are quite reliable, while being very simple, and general.

A feed-forward neural network was constructed and tested to estimate the viscosities of binary mixtures of five different types of ionic liquids with various polar and non-polar solvents within a range of temperatures. The ionic liquids investigated had various anions and consisted of either the imidazolium, ammonium, pyridinium, pyrrolidinium, or isoquinolinium cations, with various cation alkyl side-chains. Together, a total of 1996 experimental data were collected from previously published literature and divided randomly into three different datasets: 1775 data points making up the training and validation datasets, and 221 data points selected as a test dataset. The molecular weight and group structure of the ionic liquid, the molecular weight and reduced boiling temperature of the solvent, and the molar composition, temperature, and pressure of the system were selected as the independent input variables. Results indicated that the network structure presented in this study is capable to estimate the viscosity of such nonideal binary mixtures, consisting of a range of ionic liquids and solvents, with an average relative error of 0.6%.

No literature data are available on the phase behavior of binary or ternary systems involving acetaldehyde, Versatic 10, and Veova 10. This experimental study presents bubble point curves within a temperature range of 295–350 K for the two binaries of acetaldehyde + Versatic 10 and acetaldehyde + Veova 10 at several concentrations. Bubble point data are also presented for the ternary system acetaldehyde + Versatic 10 + Veova 10. The Cailletet equipment was used for the measurements, which operates according to the synthetic method. The measured bubble point pressures increased with increasing temperature and reached up to 3 bar within the concentration and temperature range investigated.

The binary systems of water + biodiesel and ternary systems of methanol + glycerol + biodiesel, which are involved in the biodiesel production process, were investigated in order to find the corresponding equilibrium data. In the case of binary systems, water solubilities in two biodiesels from either corn or frying oil were determined within a temperature range of 297.2–333.2 K. For the ternary mixtures of methanol + glycerol + either corn or frying oil biodiesel, the binodal curves and tie lines were determined at the three temperatures of 293.2, 303.2, and 313.2 K. Results showed that the solubilities in both binary and ternary systems increased with increasing temperature. The Othmer–Tobias correlation was applied to each ternary system to ascertain the reliability of the experimental tie line data obtained, and to provide phase equilibrium correlations at conditions where data are not available. All of the investigated systems were also modeled using the UNIQUAC model. The satisfactory results obtained indicate the suitability of this model for such systems.

The use of ionic liquids is being increasingly investigated in separation technologies, for example, in special distillation processes such as azeotropic or close-boiling mixtures. Such applications require accurate knowledge of the physical properties of the mixtures involved. In this respect, the correlation or estimation of the bubble points might be difficult due to the complex nature of some ternary systems, especially in the presence of ionic liquids. In the present study, the bubble points of several ternary mixtures containing an ionic liquid were correlated using an artificial neural network modeling approach. The solvents investigated consisted of 1-propanol, 2-propanol, ethyl ethanoate, methyl ethanoate, chloroform, propanone, ethanol, methanol and water and the ionic liquids considered were 1-ethyl-3-methylimidazolium trifluoromethane-sulfonate ([emim][CF3SO3]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]). For this purpose, a total of 529 experimental data points from previously published literature were collected to aid in finding the best network architecture and the optimum parameters. To do this, the collected data were divided into two subsets, namely the training and testing subsets. Using the training data set, and based on a trial and error procedure, the optimum network parameters were determined to be three layers including one input, one hidden and one output layer, nine neurons in the hidden layer, the logarithmic-sigmoid transfer function for the hidden layer, and the purline function for the output layer. The optimized weights and biases were also obtained and presented. The feasibility of the proposed network for the correlation of ternary bubble point was then examined using data that were not used in optimizing the network. The overall average absolute relative deviation (AARD %), mean square error (MSE), maximum deviation (Emax), minimum deviation (Emin) and correlation coefficient (R2) were calculated to be 0.20%, 0.9953, −0.97, 0.87 and 0.95, respectively.

The unique physical properties of ionic liquids play a decisive part in many of their applications. Therefore, the ability to predict the physical properties of ionic liquids is extremely important for the rational design of proper ionic liquids with specific properties. In practice, the processes involving ionic liquids usually contain other components, in addition to the ionic liquids. Therefore, in addition to pure component properties, knowledge of the physical properties of mixtures are also crucial for various applications. In the present study, the feasibility of using a feed-forward multi-layer perceptron neural network (MLPNN) model was investigated to predict the electrical conductivity of the ternary mixtures of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF 6 ]) + water + ethanol and [bmim][PF 6 ] + water + acetone in the temperature range from 288.15 K to 308.15 K, consisting of 104 data points. Not only were different networks, namely the linear and the hyperbolic tangent sigmoid transfer functions, considered in this study, but also the effects of the number of hidden layers, hidden neurons and the training algorithm were investigated on the accuracy of the results using 78 data points as training data to minimize the average absolute relative deviation percent (AARD%), mean square error (MSE) and correlation coefficient ( R 2 ). Among the various cases studies, statistical analyses indicated the best configuration of the network to include one hidden layer and seven neurons in the hidden layer. The optimum network was then validated using 26 data points (test data) not used in the training stage which indicated the good interpolative ability of the trained network with AARD% = 1.44, MSE = 2.87 × 10 −8 and R 2 = 0.9981.

Solubility data of methane in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide are presented within temperature and pressure ranges of 300–450 K and 1–16 MPa, respectively. Experiments were carried out in a view-cell based on the synthetic method. Results indicated rather low methane solubility in the ionic liquid, ranging from 3 up to 22 mole% at the higher pressure limit of 16 MPa. In comparison to some other gases of concern to ionic liquid gas purification membranes, methane had much lower solubility than carbon dioxide and higher solubility than hydrogen. Isothermal methane solubility was shown to increase with pressure in an almost linear manner. However, temperature effects were more predominant at low temperatures, i.e. increasing the temperature caused a more notable decrease in solubility at lower temperatures than at higher temperatures. Solubility results of methane are also compared to those of ethane, propane and butane in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Methane is by far less soluble than ethane, propane, and butane.

In this work, the phase behaviour of the binary system of carbon dioxide and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) has been studied experimentally. The equipment used for the experiments is the Cailletet set-up, based on visual observations of phase transitions of systems with constant overall composition. Results are reported for carbon dioxide concentrations ranging from 12.3 to 59.3 mol%, and within temperature and pressure ranges of 310–450 K and 0–15 MPa, respectively. The data reveal an extremely high capacity of the selected ionic liquid for dissolving CO2 gas, for example, reaching up to about 60 mol% within the above-mentioned pressure and temperature range. Also, the solubility of CO2 in the ionic liquid [emim][Tf2N] is compared to the solubility of CO2 in the ionic liquid [emim][PF6], an ionic liquid that shares the same cation.

In this experimental investigation, the bubble points of three binary mixtures consisting of propylene oxide + ethyl benzene, propylene oxide + 2-methylpentane, and propylene oxide + 2-methyl-1-pentene were determined. The method of experimentation was the synthetic method in which phase change for a mixture of constant overall composition is observed visually by varying pressure at constant temperature. Each binary system was measured for a range of concentrations. Temperatures and pressures also varied from 323 K to 373 K and up to 5 bar, respectively. It is observed that the solubility of propylene oxide varies, in increasing order, in 2-methylpentane, 2-methyl-1-pentene, and ethyl benzene, with the solubility being far greater in ethyl benzene compared to either 2-methylpentane or 2-methyl-1-pentene. (C) 2013 Published by Elsevier B.V.

Instead of the usual single-domed retrograde dew point curves, S-shaped dew point loci may occur in the isothermal pressure–composition diagram of the binary system methane+butane. This phenomenon has the consequence that at and immediately below the critical temperature of methane, isotherms are present showing triple-valued dew points for a fixed concentration. A similar behavior was observed in the binary system methane+pentane. However, in the latter system, in a narrow concentration range at temperatures slightly above the critical temperature of methane, isotherms were determined experimentally showing even two domes in the dew point loci, indicating quadruple-valued dew points at a given concentration. The latter behavior leads to the phenomenon of double retrograde vaporization, i.e. in a pressure–composition diagram at a fixed value of the concentration, the following sequence of phase transitions occur when going from low to high pressures: gas→liquid+gas→gas→liquid+gas→fluid. This paper presents bubble, dew and critical point data for the binary system ethane+limonene at five different compositions ranging from 99.50 to 99.93 mol% ethane. The data range within temperatures and pressures of 280–330 K and 3–6 MPa, respectively. This system also exhibits triple- and quadruple-valued dew points at certain concentrations, i.e. this binary system also shows the phenomenon of double retrograde vaporization. The results indicate that a very minor change in the concentration can vary the shape of dew point curve significantly.

Three-phase equilibria liquid–liquid–vapor of quasi-binary mixtures of near-critical carbon dioxide with certain 1-alkanols, ranging from butanol to hexanol, were determined experimentally for 11 different compositions. The phase transitions were determined visually using the Cailletet apparatus within a temperature range 270