Experimental Infinite Dilution Activity Coefficients Research Articles

Determination of Infinite Dilution Activity Coefficients of Molecular Solutes in Ionic Liquids and Deep Eutectic Solvents by Factorization-Machine-Based Neural Networks

Widely known as “green solvents,” ionic liquids (ILs) and deep eutectic solvents (DESs) have been used as substitutes for traditional organic solvents in separation science. To achieve better separations using ILs and DESs, this work aimed to predict the infinite dilution activity coefficients (IDACs) of molecular solutes in these solvents with the state-of-the-art factorization-machine-based neural network (DeepFM). DeepFM combines the benefits of factorization machines and deep neural networks to learn both low-order and high-order interactions among features. The IDAC prediction model was established with 52,372 experimental IDAC datapoints including 260 solvents (252 ILs and 8 DESs) and 112 molecular solutes collected at various temperatures from 288.15 to 428.15 K. Chemical information describing the ILs, DESs, and molecular solutes was included in the IDAC prediction model, including chemical functional groups, molecular weights, and Abraham solvation parameters. The IDAC prediction model showed an improved accuracy compared with alternative models; additionally, DESs were included in the IDAC prediction model for the first time. The model will reduce the energy and resources needed to optimize the selection of ILs and DESs for specific separations, which will promote the development of these green solvents for sustainable chemical processes.

Measurements of infinite dilution activity coefficient for aromatic and aliphatic hydrocarbons in Deep Eutectic Solvent, 1-ethyl-1-methylpyrrolidinium bromide + ethylene glycol at different temperatures and a stated molar ratio

It is reported data concerning the thermodynamic properties of organic mixtures in pyrrolidinium based DES with ethylene glycol at different temperatures ranging from T = 313.15 to 343.15 K. The infinite dilution activity coefficients (IDACs) for 32 various organic solutes (e.g., alkanes, alkenes, alkynes, aromatics, cycloalkanes, cycloalkenes, alcohols, and ketones) as part of the limiting thermodynamic properties were studied using Gas Liquid Chromatography (GLC). The excess thermodynamic properties (enthalpies, entropies, and Gibbs free energies) were subsequently calculated from the experimental infinite dilution activity coefficients. Moreover, the values of the selectivities and capacities at infinite dilution were determined from the experimental infinite dilution activity coefficients achieved at the fixed experimental temperature, T = 313.15 K. The obtained selectivity and capacity values were compared to those found in the literature. Lastly, the results of the investigated [[EMPYR]Br + EG] DES in a molar ratio of 1:4 proved that this investigated system could be utilized for all the selected separation problems: benzene/toluene, cyclohexane/benzene, acetone/ethanol, and n-butanol/MEK.

Infinite Dilution Activity Coefficient Measurements for 1-Methyl-4-(1-methylethenyl)-cyclohexene as a Green Solvent for Separation

Infinite dilution activity coefficients for various solutes, which include alkanes, alkenes, alkynes, cycloalkanes, heterocycles, alcohols, aromatics, ketones, ethers, nitrile, and water, in a 1-methyl-4-(1-methylethenyl)-cyclohexene solvent were measured using gas–liquid chromatography at 303.15, 313.15, and 323.15 K. The focus of this study was to assess 1-methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation processes. 1-Methyl-4-(1-methylethenyl)-cyclohexene, a nonpolar monoterpene solvent extracted from essential oils of citrus peels, was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Through experimental infinite dilution activity coefficients, γ13∞, the values of partial molar excess enthalpy at infinite (ΔHiE,∞) were obtained using the Gibbs–Helmholtz equation. The infinite dilution selectivity (Sij∞) and capacity (Δkj∞) values were calculated from the experimental limiting activity coefficients and were compared with deep eutectic solvents, ionic liquids, and industrial solvents. From this study, it was observed that 1-methyl-4-(1-methylethenyl)-cyclohexene is not suitable to be used as an alternative for separation processes. In addition, activity coefficients at infinite dilution of different organic solutes in hexadecane were measured at various temperatures to validate the reliability and accuracy of gas–liquid chromatography. Finally, the experimental data were modeled using Aspen Plus, compared with experimental data, and found to be in good agreement.

Prediction of infinite dilution activity coefficient of alcohol in ionic liquids using group contribution method

Group contribution (GC) method is one of the predictive models used to estimate the thermodynamics properties of a compound. In this work, GC is applied to develop a predictive model to estimate the infinite dilution activity coefficient (IDAC) of ethanol and propanol in ionic liquids (ILs). Developing a GC model is easier compared to other models that require 3 or more parameters. GC method has rarely been used to estimate the chemical potential of alcohol solutes in ILs. Thus, a simple two parameters van't Hoff model using multiple linear regression (MLR) is applied and fitted by generalized reduced gradient (GRG) non-linear algorithm to calculate the IDAC values of alcohol solutes in ILs. The GC model predicted IDAC values that are based on the structure of interacting species is then, compared to the experimental values obtained from literature. The developed model is known to be in best performance if the differences between predicted and experimental IDAC values are at the least. The percentage of difference or deviation between the estimated and experimental IDAC values was determined using the absolute average relative deviation (AARD). 46 ILs with varying anions and cations are used in developing a predictive model at different temperature based on the alcohol solutes. An overall AARD value of 7.49% and 9.91% is obtained from ethanol and propanol solute, respectively, that was formed by the combination of training and validation set. The efficiency of the model with lesser than 10% deviation has been validated by the comparison between predicted and experimental IDAC values based on anion, cation headgroup, and alkyl chain length. Hydrogen bonding basicity of anion and an increase in the alkyl chain of cation headgroup contribute an important role in their interaction with ethanol and propanol as a notable reduction of IDAC values could be observed. The effect of IL's structural characteristics on IDAC is discernible, which aids in designing several ILs that have enhanced interaction with alcohol solutes.

Extending the UNIFAC model for ionic liquid–solute systems by combining experimental and computational databases

AbstractConsidering that the predictive UNIFAC model is highly valuable for the solvent selection, process design and optimization of separation tasks, a large extension of this model to ionic liquid (IL)–solute systems is presented by combining experimental and COSMO‐RS derived databases. The experimental infinite dilution activity coefficient (γ∞) data of different solutes in ILs are first collected exhaustively to extend UNIFAC‐IL to cover all involved IL and conventional functional groups. Afterwards, the experimental and COSMO‐RS calculated γ∞ are compared for different types of solutes to evaluate the potential of using COSMO‐RS predictions as quasi‐experimental data for further UNIFAC‐IL extension. In the cases where COSMO‐RS can provide quantitatively accurate predictions after calibration, additional γ∞ database is specifically generated to regress more group interaction parameters in the UNIFAC‐IL model. Finally, a large experimental liquid–liquid and vapor–liquid equilibria database is collected and employed to evaluate the predictive performance of the obtained γ∞‐based UNIFAC‐IL model.

Abraham model correlations for solute transfer into 2-methyl-2-butanol based on measured activity coefficient and solubility data at 298.15 K

Experimental infinite dilution activity coefficients, gas-to-liquid partition coefficients and mole fraction solubilities are reported for numerous liquid and solid organic compounds dissolved in 2-methyl-2-butanol at 298.15 K. Experimental values were determined using headspace chromatographic and spectroscopic methods of analysis. Abraham model correlations were developed by combining our measured values with solubility data gathered from the published chemical literature. The mathematical correlations that we have developed described the measured partition coefficient and solubility data to within 0.14 log units (or less).

Thermodynamic properties of infinitely diluted solutions of organic solutes in in silico designed task-specific ionic liquid

New experimental infinite dilution activity coefficients (IDACs) of 45 different molecular solutes (alkanes, cycloalkanes, alkenes, alkynes, aromatics, alcohols, ethers, ketones, thiophene, acetonitrile, pyridine and 1-nitropropane) in the novel ionic liquid 1-(3-cyanopropyl)-1-methyl pyrrolidinium thiocyanate are presented. The considered IL has been in silico designed in our previous work by using empirical group contribution method for IDAC calculation. The experimental results shown in this paper are discussed in terms of the strength and the chemical nature of mutual interactions between the IL and the molecular solutes. An effect of nitrile group is elucidated by means of comparison of the measured data with those reported in the literature for non-functionalized counterpart of the studied IL. Furthermore, an impact of the studied “task-specific” cation on the infinite dilution selectivity in thiophene/n-octane separation problem is highlighted. The entire data set presented herein is analyzed using linear solvation-energy relationship (LSER), regular solution theory and conductor-like screening model for real solvents (COSMO-RS).

Tetramethylammonium chloride + glycerol deep eutectic solvent as separation agent for organic liquid mixtures: Assessment from experimental limiting activity coefficients

Solute retention data acquired by gas-liquid chromatography were used to determine the activity coefficients at infinite dilution for 24 organic solutes in the deep eutectic solvent (DES) consisting of tetramethylammonium chloride and glycerol in a molar ratio of 1.001:2. The organic solutes included alk-1-anes, alk-1-enes, alk-1-ynes, cycloalkanes, alkanols, alkylbenzenes, ketones, esters and heterocyclics. The measurements were undertaken at four different temperatures, viz T = (313.15, 323.15, 333.15 and 343.15) K with an estimated uncertainty of ±3.8%. From the experimental infinite dilution activity coefficient data, the values of partial molar excess enthalpy at infinite dilution were calculated using Gibbs Helmholtz relationship. Limiting selectivity and capacity values were also calculated from experimental limiting activity coefficients and compared to those of other separation agents, including other deep eutectic solvents, ionic liquids and industrial molecular agents. Results obtained in this study indicate that tetramethylammonium chloride + glycerol DES can potentially be used as an alternative solvent for nitrogen and sulphur removal from transportation fuels as well as the separation of cycloalkanes, aromatics and esters from light alkanols.

Determination of Abraham Model Correlations for Solute Transfer into Propyl Acetate Based on Experimental Activity Coefficient and Solubility Data

Experimental infinite dilution activity coefficients, gas-to-liquid partition coefficients, and molar solubility data have been measured for numerous organic solutes dissolved in propyl acetate. Results of our experimental measurements, combined with published solubility data retrieved from the published literature, have been used to derive Abraham model correlations for describing solute transfer into propyl acetate. The derived Abraham model correlations describe the experimental data to within 0.11 log10 units. Calculation of Abraham model solute descriptors for boscalid was illustrated using our derived solute transfer correlations into propyl acetate. Predictions using the calculated solute descriptors indicate that boscalid would show significant partitioning into the skin and fat tissues in the body, and would exhibit considerable baseline toxicity towards the eight aquatic organisms (five fish species and three water flea species).

Abraham model correlations for estimating solute transfer of neutral molecules into anhydrous acetic acid from water and from the gas phase

Experimental infinite dilution activity coefficient data, gas-to-liquid partition coefficient data, and solubility data have been combined from the published literature for neutral organic molecules and inert gases dissolved in anhydrous acetic acid. The compiled experimental data were transformed into molar solubility ratios, water-to-acetic acid (P) and gas-to-acetic acid (K) using standard thermodynamic relationships. The derived Abraham model correlations described the observed solubility and partition coefficient data of neutral organic compounds to within 0.18 log units (or less). Our analysis further showed that acetic acid solvent has considerable hydrogen-bond acidity, in agreement with the proposed linear structure for the solvent, and in terms of solubility related properties is not an unusual solvent at all.

Thermodynamic Insights in the Separation of Cellulose/Hemicellulose Components from Lignocellulosic Biomass Using Ionic Liquids

This work reports on the ionic liquid (IL) based separation of cellulose/hemicellulose from lignocellulosic biomass, by means of macroscale predictions using the COnductor like Screening MOdel for Real Solvents (COSMO-RS) model that is based on a statistical mechanical framework. For the benchmarking studies the experimental infinite dilution activity coefficient values for 13 components were predicted in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulphonyl}imide with an average absolute deviation (%AAD) of 15 %. Further, the solid–liquid equilibria of glucose, fructose, galactose, and xylose in [EMIM][EtSO4] and Aliquat®336 were predicted successfully with 15 % root-mean-square deviation. Afterwards, the selectivities were predicted at infinite dilution for cellulose/hemicellulose in 1,156 ILs with a combination of 34 cations and 34 anions. Based on these values, the ammonium-based ILs 1-methyl-4-aminotriazolium hexafluorophosphate [14MATAZ][PF6] and 4-aminotriazolium bis(oxalato(2)borate) [4ATAZ][BOB] were found to be good candidates for cellulose and hemicellulose extraction, respectively. The ILs selected using the COSMO-RS methodology were then studied qualitatively in terms of interaction energies and HOMO–LUMO energy gap. The binding energy for [1-methyl-4-aminotriazolium][PF6] + cellulose and [4-aminotriazolium][BOB] + cellulose systems are higher as compared with IL + cellulose + hemicellulose, indicating greater stability.

Simultaneous correlation of infinite dilution activity coefficient, vapor–liquid, and liquid–liquid equilibrium data with F-SAC

In this work, the recently proposed Functional-Segment Activity Coefficient (F-SAC) model is revised and extended in order to simultaneously represent infinite dilution activity coefficient (IDAC), vapor–liquid (VLE), and liquid–liquid (LLE) equilibrium data. For this investigation, systems involving aromatics, alkanes, cycloalkanes, alkenes and n-Formylmorpholine were selected for the tests. The behavior of these mixtures vary from nearly ideal to partially miscible. A new parameter per group was introduced in order to better represent LLE data in wide temperature ranges. The revised model was calibrated with experimental IDAC and LLE (binary and ternary systems) data. F-SAC correlation results and predictions of VLE experiments were compared with different UNIFAC parametrizations available in the literature. For the systems tested, the proposed approach showed to be more general; there were good IDAC and LLE correlations as well as VLE predictions, all with a single parameter set.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide using gas–liquid chromatography at T = (313.15, 333.15, 353.15 and 373.15) K

Activity coefficients at infinite dilution for organic solutes, which include n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes, alcohols and ketones, in the ionic liquid trihexyltetradecylphosphonium bis (trifluoromethylsulfonyl) imide were measured by gas–liquid chromatography using the latter as the stationary phase. This ionic liquid had previously been studied and reported in literature; however due to significant discrepancies in the reported infinite activity coefficient values, there was justification for further study and reporting. The temperature range investigated in this study is significantly wider and at higher temperatures than presented previously in the literature. From the experimental infinite dilution activity coefficient data at the four different temperatures T=(313.15, 333.15, 353.15 and 373.15)K, partial molar excess enthalpies at infinite dilution were calculated. Values of the selectivity for hexane/benzene and methanol/benzene separations were determined from experimental values of the activity coefficients at infinite dilution and these results were compared to literature values for other ionic liquids, as well as for industrial solvents. The capacities were also determined as it gives an indication of the solvent extraction behavior of the ionic liquid.

Assessing the reliability of predictive activity coefficient models for molecules consisting of several functional groups

Currently, the most successful predictive models for activity coefficients are those based on functional groups such as UNIFAC. In contrast, these models require a large amount of experimental data for the determination of their parameter matrix. A more recent alternative is the models based on COSMO, for which only a small set of universal parameters must be calibrated. In this work, a recalibrated COSMO-SAC model was compared with the UNIFAC (Do) model employing experimental infinite dilution activity coefficient data for 2236 non-hydrogen-bonding binary mixtures at different temperatures. As expected, UNIFAC (Do) presented better overall performance, with a mean absolute error of 0.12 ln-units against 0.22 for our COSMO-SAC implementation. However, in cases involving molecules with several functional groups or when functional groups appear in an unusual way, the deviation for UNIFAC was 0.44 as opposed to 0.20 for COSMO-SAC. These results show that COSMO-SAC provides more reliable predictions for multi-functional or more complex molecules, reaffirming its future prospects.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-butyl-3-methylimidazolium hexafluoroantimonate using gas–liquid chromatography at T = (313.15, 323.15, and 333.15) K

Activity coefficients at infinite dilution were determined for 27 solutes: n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes, alcohols, and ketones in the ionic liquid 1-butyl-3-methylimidazolium hexafluoroantimonate, [BMIM][SbF 6], by gas–liquid chromatography at three different temperatures, T = (313.15, 323.15, and 333.15) K. The results are compared to published data on related compounds. The partial molar excess enthalpy values at infinite dilution were calculated from the experimental data over the same temperature range. Selectivities and capacities at infinite dilution were calculated for the hexane/benzene and methanol/benzene systems from experimental infinite dilution activity coefficients and compared to the literature values for related ionic liquids, as well as to data on industrial molecular solvents.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid trihexyl(tetradecyl)phosphonium tetrafluoroborate using gas–liquid chromatography at T = (313.15, 333.15, 353.15, and 373.15) K

Activity coefficients at infinite dilution have been measured by gas–liquid chromatography for 27 organic solutes (n-alkanes, 1-alkenes, 1-alkynes, cycloalkanes, aromatics, alcohols, and ketones) in the ionic liquid trihexyl(tetradecyl)phosphonium tetrafluoroborate [3C 6C 14P][BF 4]. The measurements were carried out at four different temperatures viz. T = (313.15, 333.15, 353.15, and 373.15) K. From the experimental data, partial molar excess enthalpy values at infinite dilution were calculated for the experimental temperature range. The selectivity values for the separation of n-hexane/benzene, cyclohexane/benzene, and methanol/benzene mixtures were determined from the experimental infinite dilution activity coefficient values. These values were compared to those available in the literature for other ionic liquids and commercial solvents, so as to assess the feasibility of employing [3C 6C 14P][BF 4] in solvent-enhanced industrial separations.

Gas-liquid chromatography measurements of activity coefficients at infinite dilution of hydrocarbons and alkanols in 1-alkyl-3-methylimidazolium bis(oxalato)borate

The activity coefficients at infinite dilution, γ i ∞ for various solutes: alkanes, cycloalkanes, 1-alkenes, 1-alkynes, benzene, alkylbenzenes, and alcohols in the ionic liquids 1-butyl-3-methylimidazolium bis(oxalato)borate [BMIM][BOB] and 1-hexyl-3-methyl-imidazolium bis(oxalato)borate [HMIM][BOB] have been determined by gas-liquid chromatography at the temperatures ranging from 308 to 348 K. The partial molar excess enthalpies at infinite dilution H i E , ∞ of the solutes in the ionic liquids were also derived from the temperature dependence of the γ i ∞ values. The selectivities for the hexane/benzene, cyclohexane/benzene and hexane/hexene separation problems were calculated from experimental infinite dilution activity coefficient values and compared to the other ionic liquids, taken from the recent literatures.

Activity coefficients at infinite dilution of organic solutes in N-alkylpyridinium bis(trifluoromethylsulfonyl)imide ([C nPY][NTf 2], n = 2, 4, 5) using gas–liquid chromatography

The activity coefficients at infinite dilution, γ i ∞ for both polar and non-polar solutes in the ionic liquids N-alkylpyridinium bis(trifluoromethylsulfonyl)imide ([C n PY][NTf 2], n = 2, 4, 5) have been determined by gas–liquid chromatography using the ionic liquid as the stationary phase. The measurements were carried out at the temperatures from (303 to 353) K. The partial molar excess enthalpies at infinite dilution H i E, ∞ of the solutes in the ionic liquids were also derived from the temperature dependence of the γ i ∞ values. The values of the selectivity for the hexane/benzene and cyclohexane/benzene separation problems were calculated from experimental infinite dilution activity coefficient values and compared to the other ionic liquids, taken from the recent literatures.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB] using gas–liquid chromatography

The activity coefficients at infinite dilution, γ i ∞ , for both polar and non-polar solutes in the ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate [EMIM][TCB] have been determined by gas–liquid chromatography at the temperatures from (303 to 343) K. The partial molar excess enthalpies at infinite dilution H i E, ∞ of the solutes in the ionic liquid were also calculated from the temperature dependence of the γ i ∞ values. The selectivity for the hexane/benzene and cyclohexane/benzene separation problems was calculated from experimental infinite dilution activity coefficient values and compared to the other ionic liquids, taken from the recent literature.

Phase Equilibria of Mixtures Containing Glycol and n-Alkane: Experimental Study of Infinite Dilution Activity Coefficients and Modeling Using the Cubic-Plus-Association Equation of State

In this work, we report the infinite dilution activity coefficients for four n-alkanes (n-pentane, n-hexane, n-heptane, and n-octane) in monoethylene glycol in the temperature range from 298 to 334 K and at atmospheric pressure. Experimental data were measured using a previously described inert gas stripping technique. The new experimental data are compared with the literature data whenever possible. The experimental infinite dilution activity coefficients of several alkanes from n-pentane to n-hexadecane in monoethylene glycol, diethylene glycol, triethylene glycol, and tetraethylene glycol previously reported in the literature, along with the data measured in this work have been modeled using the cubic-plus-association (CPA) equation of state (EoS). Satisfactory results have been obtained using temperature-independent interaction parameters. Useful remarks are presented about the application of infinite dilution activity coefficient data for estimating binary interaction parameters of the CPA EoS for the description of whole vapor-liquid equilibria. Furthermore, the variation in the values of the interaction parameters is discussed for different glycol systems.