Limiting Activity Coefficients Research Articles

Correlating Pure Component Properties with MOSCED Solubility Parameters: Enthalpy of Vaporization and Vapor Pressure

Tools to predict vapor–liquid phase equilibria are indispensable for the conceptualization and design of separation processes. Modified separation of cohesive energy density (MOSCED) is a solubility-parameter-based method parameterized to make accurate predictions of the limiting activity coefficient. As a solubility-parameter-based method, MOSCED can not only make quantitative predictions, but can shed light on the underlying intermolecular interactions. In the present study, we demonstrated the ability of MOSCED to correlate the enthalpy of vaporization and vapor pressure at a specific temperature using multiple linear regression. With this addition, MOSCED is able to predict vapor–liquid phase equilibria in the absence of reference data. This was demonstrated for the prediction of the Henry’s constant and solvation free energy of organic solutes in water, which was found to be superior to mod-UNIFAC. In addition to being able to make phase equilibrium predictions, the ability to correlate the enthalpy of vaporization and vapor pressure offers the opportunity to include additional properties in the regression of the MOSCED parameters. Given this success, we additionally attempted to correlate a wide range of physical properties using a similar expression. While, in some cases, the results were reasonable, they were inferior to the correlations of the enthalpy of vaporization and vapor pressure. Future efforts will be needed to improve the correlations.

Gibbs–Helmholtz graph neural network: capturing the temperature dependency of activity coefficients at infinite dilution

A hybrid model that combines the Gibbs–Helmholtz equation with Graph Neural Networks for predicting limiting activity coefficients.

Prediction of azeotrope formation in binary mixtures with pure component properties and limiting activity coefficients

For a binary mixture without azeotrope, its boiling temperature at quasi-infinite dilution TbQID< Tb,H (the higher boiling temperature of the two components), and TbQID> Tb,L (the lower boiling temperature of the two components). For a binary mixture with minimum boiling azeotrope,TbQID < Tb,L at the neighbourhood of the lower-boiling-temperature component. For a binary mixture with maximum boiling azeotrope, TbQID> Tb,H at the neighbourhood of the higher-boiling-temperature component. The above phenomena are used as predicting criteria for azeotrope formation in this paper. The value of TbQID is calculated by inversely using an existing method proposed to estimate the vaporization heat of pure liquid at its normal boiling temperature. The vaporization heat of the binary mixture at quasi-infinite dilution is taken as the sum of the vaporization heats of the pure components and the mixing heat to form the mixture, where the mixing heat can be estimated with the MOSCED (modified separation of cohesive energy density) Model or other limiting activity coefficient models. The method proposed requires only pure component properties, Tb, Tc, Pc and the MOSCED parameters. The method is illustrated with 311 mixtures, and about 89% of mixtures are predicted successfully.

Excess thermodynamic functions of phosphonium-based deep eutectic solvent for various organic solutes at different temperatures

BackgroundDeep eutectic solvents have presented excellent properties and have been utilized in various research areas of chemistry. These solvents have recently been reported as one of the most fascinating with promising possibilities when compared to the other solvents. MethodIn this present study, the limiting activity coefficients have been estimated for 32 various volatile organic solutes (aliphatic and aromatic hydrocarbons, alcohols, THF, thiophene, acetonitrile, ketones) and water in [trihexyltetradecylphosphonium decanoate + ethylene glycol] prepared at 1: 4 molar ratio, respectively. Measurements were conducted at different temperatures, T = (313.15–343.15) K and at atmospheric pressure. Gas liquid chromatography coupled with thermal conductivity detector was employed to obtain the experimental retention data of solutes in the deep eutectic solvent. The partial molar excess properties, such as enthalpies, entropies, and Gibbs energies were determined at infinite dilution from the calculated limiting activity coefficients. In addition, the selectivity and capacity values for the separation problems such as (acetone/ethanol, cyclohexane/benzene, benzene/toluene, and butanol/MEK) were determined from the limiting activity coefficients. FindingsThe attained values proved that trihexyltetradecylphosphonium decanoate + ethylene glycol deep eutectic solvent could be utilized in the separation of azeotropes. The results were discussed based on the intermolecular interactions occurring in the deep eutectic solvent mixtures. The influence of the hydrogen bond donor on deep eutectic solvent behavior was discussed.

Absolute Quantitation of Serum Antibody Reactivity Using the Richards Growth Model for Antigen Microspot Titration.

In spite of its pivotal role in the characterization of humoral immunity, there is no accepted method for the absolute quantitation of antigen-specific serum antibodies. We devised a novel method to quantify polyclonal antibody reactivity, which exploits protein microspot assays and employs a novel analytical approach. Microarrays with a density series of disease-specific antigens were treated with different serum dilutions and developed for IgG and IgA binding. By fitting the binding data of both dilution series to a product of two generalized logistic functions, we obtained estimates of antibody reactivity of two immunoglobulin classes simultaneously. These estimates are the antigen concentrations required for reaching the inflection point of thermodynamic activity coefficient of antibodies and the limiting activity coefficient of antigen. By providing universal chemical units, this approach may improve the standardization of serological testing, the quality control of antibodies and the quantitative mapping of the antibody–antigen interaction space.

Solvation properties of protic ionic liquids 2-methoxyethylammonium nitrate, propylammonium hydrogen sulfate, and butylammonium hydrogen sulfate

Solvation properties of protic ionic liquids (PILs) are virtually unexplored. We measured the limiting activity coefficients of several hydrocarbons and aliphatic alcohols in 2-methoxyethylammonium nitrate (2MEAN), propylammonium hydrogen sulfate (PAHS), and butylammonium hydrogen sulfate (BAHS) at 298 K. Comparison with the previously obtained results for other substituted ammonium PILs reveals the sensitivity of solvation properties to the changes in the structure of both cation and anion which also affect the nanostructure of the bulk phase. It was shown that hydrocarbons are less soluble in 2MEAN than in alkylammonium nitrates due to destabilizing effect of the methoxy group on apolar domains in the liquid structure preferentially solvating hydrocarbon molecules. The solubility of hydrocarbons is also lower in hydrogen sulfate ILs than in nitrate ILs with the same alkylammonium cation. This can be explained by the presence of the acidic hydrogen in anion which strengthens the hydrogen bonds network and the solvophobic effects in the liquid.

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.

A smile is all you need: predicting limiting activity coefficients from SMILES with natural language processing.

The knowledge of mixtures' phase equilibria is crucial in nature and technical chemistry. Phase equilibria calculations of mixtures require activity coefficients. However, experimental data on activity coefficients are often limited due to the high cost of experiments. For an accurate and efficient prediction of activity coefficients, machine learning approaches have been recently developed. However, current machine learning approaches still extrapolate poorly for activity coefficients of unknown molecules. In this work, we introduce a SMILES-to-properties-transformer (SPT), a natural language processing network, to predict binary limiting activity coefficients from SMILES codes. To overcome the limitations of available experimental data, we initially train our network on a large dataset of synthetic data sampled from COSMO-RS (10 million data points) and then fine-tune the model on experimental data (20 870 data points). This training strategy enables the SPT to accurately predict limiting activity coefficients even for unknown molecules, cutting the mean prediction error in half compared to state-of-the-art models for activity coefficient predictions such as COSMO-RS and UNIFACDortmund, and improving on recent machine learning approaches.

Prediction of Azeotrope Formation in Binary Mixtures with Pure Component Properties and Limiting Activity Coefficients

Prediction of Azeotrope Formation in Binary Mixtures with Pure Component Properties and Limiting Activity Coefficients

ОБРАЗОВАНИЕ АЗЕОТРОПНЫХ СМЕСЕЙ N-МЕТИЛПИРРОЛИДОНА С УГЛЕВОДОРОДАМИ

Using the limiting activity coefficients of the components of binary systems of N-methylpyrrolidone with n-alkanes and the conditions for the formation of azeotropes, it is found that N-methylpyrrolidone forms azeotropic mixtures with n-alkanes С9 - С 15, with alkylbenzenes С 10 - С 12 and with naphthalene. The formation of azeotropes with saturated hydrocarbons with a boiling point of 230-270 ° C must be taken into account when developing a technological scheme for the N-methylpyrrolidone regeneration unit, and also not to use this extractant for extraction purification of raw materials with a boiling point below 230 ° C

Methods and Experimental Techniques to Research Solubility of Gases in Liquids

Experimental methods for determining the limiting activity coefficients that are relevant in the approbation of theoretical approaches to solve the problem of gas solubility in a liquid are described. Traditional methods realized on a single installation are preferred in order to obtain consistent information. The necessity of additional purification of problem samples of the studied substances is demonstrated. A developed and created low-temperature laboratory column is presented, for which the degree of separation in cases with a coil and packed rectification section, as well as the relative fugacity of the pentane — fluorodichloroethane test mixture are found. Based on the conducted experiments, it can be concluded that it is possible to efficiently use both a coil and a packed column for the purification of substances and enhancement of the measuring effect, and the possibility of obtaining reliable data on limiting solubility from the experimental installation. The gravimetric static method for measuring the concentration of the components in binary mixtures is promising for the study of little-researched and rare substances and is applicable in combination with a small volume cell.

Combining Molecular Dynamics and Machine Learning to Predict Self-Solvation Free Energies and Limiting Activity Coefficients.

Computational prediction of limiting activity coefficients is of great relevance for process design. For highly nonideal mixtures including molecules with directed interactions, methods that maintain the molecular character of the solvent are most promising. Computational expense and force-field deficiencies are the main limiting factors that prevent the use of high-throughput molecular dynamics (MD) simulations in a predictive setup. The combination of MD simulations and machine learning used in this work accounts for both issues. Comparison to published data including free-energy simulations, COSMO-RS and UNIFAC models, reveals competitive prediction accuracy.

Assessment of the SM12, SM8, and SMD Solvation Models for Predicting Limiting Activity Coefficients at 298.15 K

The SMx (x = 12, 8, or D) universal solvent models are implicit solvent models which using electronic structure calculations can compute solvation free energies at 298.15 K. While solvation free energy is an important thermophysical property, within the thermodynamic modeling of phase equilibrium, limiting (or infinite dilution) activity coefficients are preferred since they may be used to parameterize excess Gibbs free energy models to model phase equilibrium. Conveniently, the two quantities are related. Therefore the present study was performed to assess the ability to use the SMx universal solvent models to predict limiting activity coefficients. Two methods of calculating the limiting activity coefficient where compared: (1) the solvation free energy and self-solvation free energy were both predicted and (2) the self-solvation free energy was computed using readily available vapor pressure data. Overall the first method is preferred as it results in a cancellation of errors, specifically for the case in which water is a solute. The SM12 model was compared to both the Universal Quasichemical Functional-group Activity Coefficients (UNIFAC) and modified separation of cohesive energy density (MOSCED) models. MOSCED was the highest performer, yet had the smallest available compound inventory. UNIFAC and SM12 exhibited comparable performance. Therefore further exploration and research should be conducted into the viability of using the SMx models for phase equilibrium calculations.

Expanding the Solubility Parameter Method MOSCED to Pyridinium-, Quinolinium-, Pyrrolidinium-, Piperidinium-, Bicyclic-, Morpholinium-, Ammonium-, Phosphonium-, and Sulfonium-Based Ionic Liquids.

MOSCED (modified separation of cohesive energy density) is a solubility parameter method that offers an improved treatment of association interactions. Solubility parameter methods are well known for their ability to both make quantitative predictions and offer a qualitative description of the underlying molecular-level driving forces, lending themselves to intuitive solvent selection and design. Currently, MOSCED parameters are available for 130 organic solvents, water, and 33 imidazolium-based room temperature ionic liquids (ILs). In this work, we expand MOSCED to cover 66 additional ILs containing the pyridinium, quinolinium, pyrrolidinium, piperidinium, bicyclic, morpholinium, ammonium, phosphonium, and sulfonium cations using 10,052 experimental limiting activity coefficients. The resulting parameters may readily be used to predict the phase behavior in mixtures involving ILs.

Evaluation of an imidazolium-based ionic liquid as a separation solvent for binary mixtures based on limiting activity coefficient data

The separation of volatile organic solvents (herewith, solutes) were tested in an imidazolium-based ionic liquid (1,3-dimethylimidazolium dimethylphosphate), [MMIM] [DMP] as a solvent at four different temperatures, T = (313 .15 to 343.15) K and at atmospheric pressure. The solutes include alcohols, aromatic hydrocarbons, thiophene, ketones, alkanes, alkynes, alkenes, acetonitrile, THF, as well as water. The separation potential of the investigated ionic liquid was based on the activity coefficients at infinite dilution, γ13∞, of organic solutes. This was based on the retention data acquired by gas liquid chromatography. Excess thermodynamic parameters at infinite dilution such as Gibbs free energy, ΔG1E,∞, entropy term, TrefΔS1E,∞ and partial molar enthalpy, ΔH1E,∞ were determined from the γ13∞ data. The results are discussed in terms of intermolecular interactions occurring between the solutes under investigation and the ionic liquid. The effectiveness of 1,3-dimethylimidazolium dimethylphosphate to separate some of the separation problems discussed in this work is determined from the selectivity and capacity values calculated from the limiting activity coefficients at infinite dilution. These thermodynamic functions can be used to develop, design or optimise industrial extraction processes.

MOSCED parameters for 1-n-alkyl-3-methylimidazolium-based ionic liquids: Application to limiting activity coefficients and intuitive entrainer selection for extractive distillation processes

Solubility parameter based methods have long been valuable design tools due to their ability to make both quantitative predictions and to shed insight into the underlying intermolecular interactions. The use of MOSCED (modified separation of cohesive energy density) is particularly attractive due to its advanced treatment of association interactions. Nonetheless, the use of MOSCED is limited due to its relatively small parameter matrix. Here, we work to expand MOSCED to cover room temperature ionic liquids (ILs) by regressing parameters for 33 ILs with the common imidazolium based cation. The ability to use MOSCED for intuitive solvent selection is demonstrated by identifying promising IL entrainer candidates to break an example minimum and maximum boiling binary azeotropic system using extractive distillation.

Contrasting the solvation properties of protic ionic liquids with different nanoscale structure

The limiting activity coefficients of several hydrocarbons and aliphatic alcohols in protic ionic liquids: 2-hydroxyethylammonium nitrate (EOAN), propylammonium nitrate (PAN), butylammonium nitrate (BAN), and butylammonium thiocyanate (BASCN), were determined at 298K using gas chromatographic headspace analysis. The activity coefficients of hydrocarbons in EOAN turned out to be much higher than in BASCN or alkylammonium nitrates. The methylene group increments for the Gibbs free energies of solvation of various homological series in EOAN are also much higher than in BASCN, BAN, PAN as well as in aprotic ionic liquids or molecular solvents except water. Water-like solvation properties of EOAN are linked with the presence of a three-dimensional network of hydrogen bonds, high concentration of ion pairs, and the absence of nanoscale domain structure that exists in liquid alkylammonium salts and favors solvation of hydrocarbons in apolar domains. The sensitivity of solvation properties of PILs to their nanostructure suggests that the presence of apolar and polar domains in a liquid can be probed with the studies of solvation thermodynamics.

Experimental Data of Fluid Phase Equilibria- Correlation and Prediction Models: A Review

The examples of phase equilibria in binary systems, solid/liquid (SLE), liquid/liquid (LLE), vapor/liquid (VLE), as well as liquid/liquid equilibria in ternary systems mainly containing ionic liquids (ILs), or the infragrance materials, or pharmaceuticals with molecular organic solvents, such as an alcohol, or water, or hydrocarbons, are presented. The most popular correlation methods of the experimental phase equilibrium data are presented, related to the excess Gibbs free energy models such as Wilson, universal-quasichemical, UNIQUAC and non-random two-liquid model, NRTL as well as several popular theories for the modeling of the phase equilibria and excess molar enthalpy, HE in binary or ternary mixtures are presented: the group contribution method (Mod. UNIFAC) and modified UNIFAC model for pharmaceuticals and lattice theory based on non-random hydrogen bonding (NRHB). The SLE, LLE, or VLE and HE of these systems may be described by the Perturbed-Chain Polar Statistical Associating Fluid Theory (PC-SAFT), or a Conductor-like Screening Model for Real Solvents (COSMO-RS). The examples of the application of ILs as extractants for the separation of aromatic hydrocarbons from alkanes, sulfur compounds from alkanes, alkenes from alkanes, ethylbenzene from styrene, butan-1-ol from water phase, or 2-phenylethanol (PEA) from water are discussed on the basis of previously published data. The first information about the selectivity of extrahent for separation can be obtained from the measurements of the limiting activity coefficient measurements by the gas–liquid chromatography technique. This review outlines the main research work carried out over the last few years on direct measurements of phase equilibria, or HE and limiting activity coefficients, the possibility of thermodynamic modeling with emphasis on recent research achievements and potential for future research.

Refining of Diesel and Ship Fuels by Extraction and Combined Methods. Part 1. Use of Ionic Liquids as Extractants

Modern and perspective environmental requirements to the quality of diesel and ship fuels are considered. Data on the selectivity and solvency of ionic liquids with respect to aromatic hydrocarbons and heterocyclic sulfur- and nitrogen-containing compounds, obtained using gas-chromatographic data on the limiting activity coefficients of model mixture components in ionic liquids, are discussed. Experimental data on the liquid-liquid phase equilibrium in model systems consisting of a saturated hydrocarbon, an aromatic sulfur- or nitrogen-containing compound, and an ionic liquid and on the component distribution ratios and separation factors are presented. The advantages and drawbacks of ionic liquids as extractants in selective refining of diesel fractions and vacuum gasoils to obtain raffinates meeting perspective environmental requirements to diesel and ship fuels are considered.

Dissociation Constants of Hydrohalic Acids HCl, HBr, and HI in Aqueous Solutions

The acid dissociation constants (Ka) of HCl, HBr, and HI are determined using the equation $${{K}_{{\text{a}}}} = K_{{\text{a}}}^{'}f_{{{\text{HA}}}}^{\infty }$$ , where $$K_{{\text{a}}}^{'}$$ is the apparent dissociation constant and $$f_{{{\text{HA}}}}^{\infty }$$ is the activity coefficient of an undissociated molecule in an infinitely dilute aqueous solution. Apparent dissociation constants $$K_{{\text{a}}}^{'}$$ are calculated using reliable reference data. Limiting activity coefficients $$f_{{{\text{HA}}}}^{\infty }$$ are calculated using the COSMO-RS approach. The validity of the results is confirmed by comparing them and the known $$f_{{{\text{HA}}}}^{\infty }$$ values for similar compounds.