Infinite Dilution Data Research Articles

Pre-screening of an eco-friendly solvent for separating industrial mixtures: A useful tool for solvent selection

In this work, gas liquid chromatography was used to obtain the retention data of volatile organic solvents (here referred as solutes) at different temperatures, T = (313.15 - 353.15) K and at atmospheric pressure. The retention data obtained was used to compute the activity coefficients at infinite dilution. The solvent was prepared by the combination of 1‑butyl‑2,3-dimethylimidazolium chloride and diethylene glycol at 1:2 molar ratio and was used as a stationary phase to evaluate intermolecular interactions of various volatile organic solvents, including (aromatic hydrocarbons, ketones, alkanes, alkenes, alkynes, alcohols, thiophene, acetonitrile and tetrahydrofuran). Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectroscopy were utilized to determine any possible shifts when the two compounds were assorted. TGA/DSC 1 was also utilized to determine the thermal stability of the investigated solvent and to confirm that there will be no bleeding on the column loading when operated at T = (313.15 - 353.15) K. The excess thermodynamic properties at infinite dilution including enthalpies, Gibbs free energies and entropy term were computed to further explain the types of interactions occurring between the systems. The activity coefficients at infinite dilution data were used to calculate the separation parameters (selectivity and capacity) to evaluate the feasibility of the solvent in separating the industrial mixtures. Values pertaining to selectiveness and capacity were evaluated and compared to other extracting solvents found in literature for the separation of azeotropic mixtures. The attained activity coefficients at infinite dilution data reveals that the investigated solvent better separate solutes at low temperatures and this is an added advantage when using 1‑butyl‑2,3-dimethylimidazolium chloride to diethylene glycol. In addition, the investigated solvent was found suitable for the extraction of azeotropic mixtures comprising alkanes and alcohols.

Measurement of Activity Coefficients at Infinite Dilution for Various Organic Solutes in Deep Eutectic Solvent (1-Butyl-2,3-dimethylimidazolium Chloride + Ethylene Glycol) at Different Temperatures

Activity coefficients at infinite dilution (γ13∞) for organic solutes in deep eutectic solvent (DES) prepared by {1-butyl-2,3-dimethylimidazolium chloride (BDMIM Cl) + ethylene glycol (EG)} at a molar ratio of 1:3 have been measured using the gas–liquid chromatographic method (GLC). The thermal stability of the entrainer was determined by the thermogravimetric analyzer. The measurements were carried out in the temperature range of T = (313.15 to 343.15) K and at atmospheric pressure. The values of the partial molar excess enthalpies at infinite dilution (H1E,∞) were derived from the temperature dependence of the γ13∞∞ values. The entropies (Tref ΔS1E,∞) and Gibbs energies (ΔG1E,∞) of organic solutes at a reference temperature Tref = 323.15 K were also calculated from the γ13∞ values. These excess thermodynamic functions were calculated to further explain the intermolecular interactions occurring between the volatile organic solvents and the prepared deep eutectic solvent. Important separation parameters such as selectivities (Sij∞) and capacities (Kj∞) at infinite dilution were computed from the activity coefficients at infinite dilution data at T = 313.15 K. Selectivity and capacity data were calculated for the industrial mixtures such as cyclohexane/benzene, hexane/thiophene, cyclohexane/ethanol. There results were compared to the literature data comprising deep eutectic solvents and ILs with the cation of 1-butyl-3-methylimidazolium. The investigated solvent was found suitable to separate azeotropes formed by alkanes/alcohols.

Influence of hydrogen bond donor on zinc chloride in separation of binary mixtures: Activity coefficients at infinite dilution

Deep eutectic solvents are solvents similar to the ionic liquids (ILs) but less expensive and simple to prepare than ILs. The activity coefficients at infinite dilution of solutes in the deep eutectic solvents (DESs) plays an important role in designing of the separation processes. Gas liquid chromatography technique (GLC) was used to determine activity coefficients at infinite dilution for 34 polar and non-polar organic solutes: solutes include alkanes, alkenes, alcohols, ketones, thiophene, heterocyclics, cycloalkanes, acetonitrile, tetrahydrofuran, cycloalkenes, aromatic hydrocarbon and water in two zinc chloride based DESs [zinc chloride + acetic acid] (1:4) and [zinc chloride + phosphoric acid] (1:2.5) at temperatures (313.15, 323.15, 333.15, 343.15, 353.15) K. Excess thermodynamic parameters [partial molar excess enthalpies ΔG1E,∞,entropies(TrefΔS1E,∞) and Gibbs free energies (ΔG1E,∞)] were derived from activity coefficient at infinite dilution data. The selectivity and capacity values for separation of benzene/ethanol, cyclohexane/ethanol, n-octane/acetonitrile, ethylbenzene/butan-1-ol, n-heptane/butan-1-ol at T = 323.15 K were calculated and compared to literature values for DESs, ionic liquids (ILs), and sulfolane to assess the suitability of the DESs for possible use as an entrainers. Both DESs [zinc chloride + acetic acid] (1:4) and [zinc chloride + phosphoric acid] (1:2.5) have high selectivity values as compared to studied ionic liquids as well as conventional solvents in the literature for difficult separation system of benzene/ethanol, cyclohexane/ethanol, ethylbenzene/butanol and heptane/butanol which indicate that these DESs are an extraction solvent and has separation ability for difficult separation system of benzene/ethanol, cyclohexane/ethanol, ethylbenzene/butan-1-ol and n-heptane/butan-1-ol.

Thermodynamic properties and activity coefficients at infinite dilution for different solutes in deep eutectic solvent: 1-butyl-3-methylimidazolium chloride + glycerol

Activity coefficients for 33 solutes at infinite dilution were determined in deep eutectic solvent (1-butyl-3-methylimidazolium chloride + glycerol) prepared by a molar ratio of 2 [BMIM] [Cl]: 1 glycerol. The retention data of solutes in prepared deep eutectic solvent (DES) as an extracting solvent were obtained with the aid of gas liquid chromatography (g.l.c) operated at different temperatures, T = (313.15–343.15) K and at ambient pressure. The separation capacity and molecular interactions of solutes in DES were determined from the activity coefficient measurements. The intermolecular interactions were further expressed by calculating thermodynamic functions including partial molar enthalpies (∆H1E, ∞), Gibbs free energy (∆G1E, ∞), and entropy term (Tref∆S1E, ∞), at infinite dilution. These were calculated from the activity coefficients at infinite dilution data. The activity coefficient data was also used to compute the separation parameters (selectivity and capacity) for selected industrial extraction problems (hexane/benzene; cyclohexane/benzene; acetone/ethanol and cyclohexane/ethanol). Activity coefficients data are important as they can be used for pre-screening of separation solvents for industrial extraction processes.

Application of trihexyltetradecylphosphonium dicyanamide ionic liquid for various types of separations problems: Activity coefficients at infinite dilution measurements utilizing GLC method

In this work, the ionic liquid trihexyltetradecylphosphonium dicyanamide [P 6 6 6 14] [DCA] was evaluated as a potential extraction solvent for organic compounds. The assessment was done based on the solute retention data obtained by gas liquid chromatography (GLC) for 33 solutes: (alkanes, alkenes, ketones, alcohols, alkynes, aromatic hydrocarbons, tetrahydrofuran, thiophene, acetonitrile and water). The experiment was conducted at a series of four temperatures (313.15–343.15) K at 10 K intervals. Experimental activity coefficients at infinite dilution data acquired over the investigated temperature range was then utilized to compute the thermodynamic functions at infinite dilution including partial molar excess enthalpy, ΔH1E,∞, Gibbs free energy, ΔG1E,∞ and entropy term, TrefΔS1E,∞. The selectivity and capacity values for some of the separation challenges (heptane/thiophene, water/butanol and heptane/benzene) were computed from the γ13∞ data and in contrast to the other phosphonium based ionic liquids in the literature. The selectivity and capacity data shows that the investigated ionic liquid can be utilized in the separation of heptane/thiophene or water/butan-1-ol mixtures.

Activity coefficients at infinite dilution of organic solutes in methylphosphonate based ionic liquids using gas-liquid chromatography

Activity coefficients at infinite dilution γ12∞ were determined for organic solutes in two ionic liquids 1-ethyl-3-methylimidazolium methylphosphonate [EMIM][(MeO)(H)PO2] and 1.3-dimethylimidazolium methylphosphonate [DMIM][(MeO)(H)PO2] by gas-liquid chromatography at temperatures within the range (313.15 to 373.15)K. The values of the selectivity and capacity for few separation problems cyclohexane/benzene, cyclohexane/thiophene and cyclohexane/pyridine were calculated from activity coefficients at infinite dilution data and compared to literature values for other ionic liquids and some industrial solvents such as sulfolane, N-methyl-2-pyrrolidone (NMP) and N-formylmorpholine (NFM). The selectivity values of both ILs investigated in this study are greater than that for NMP, NFM, and sulfolane. These results indicate the potential use of the two ILs in extractive separation processes.

DETERMINATION OF INFINITE DILUTION ACTIVITY COEFFICIENT IN ETHANOL-WATER-SALT SYSTEMS USING SPME-GC-FID

A new method using the headspace solid phase microextraction (HS-SPME) technique was used to evaluate the infinite dilute activity coefficient (γ1∞) in an alcohol/water/salt system. The studied systems were ethanol and water with NaCl and NH4Cl at salt concentrations of 5, 10, 15, and 30% m/v and temperatures of 303.15 and 313.15 K. The method was used to investigate the salt effect on vapor/liquid equilibrium in an ethanol/water system, yielding satisfactory results. The study focused on the rich side in ethanol. The data were compared with the literature infinite dilution data determined by other methods such as differential ebulliometry (EBUL), differential static cell equilibrium (STAT), and gas-liquid chromatography with no gas phase correction (GC). In this study, NaCl showed better separation rates than NH4Cl.

Extrapolation/interpolation of infinite dilution, activity coefficient as well as liquid and solid solubility between solvents: Part 1. Alkane solvents

Infinite dilution activity coefficients play a vital role in modeling of phase and chemical equilibrium behavior. From the dependence of the limiting activity coefficient of a solute on the solvent, important properties like liquid and solid solubility in these solvents can be deduced. Although a large amount of experimental information is available in the open literature as well as from thermophysical data banks such as the Dortmund Data Bank (DDB), the behavior of high boiling solutes in low boiling solvents is often not known, partly due to difficulties in experimental determination.A method for the extrapolation of infinite dilution activity coefficients and thus the liquid and solid solubility of any solute in different solvents within one solvent family is under development. Results of a method applicable to any solute in a large variety of different saturated hydrocarbon compounds are presented in this paper.In this method, the activity coefficient is assumed to consist of a combinatorial and residual contribution. In the case of alkane solvents, only this combinatorial contribution changes when going from one solvent to another. Several well known combinatorial expressions were evaluated and were found to produce poor extrapolations in many instances. Quite surprisingly, free-volume combinatorial expressions performed best even for some of the rather low molecular weight compounds used in this test.A new empirically modified free-volume expression is proposed which allows for accurate extrapolation. Additional activity coefficient data have been determined via GLC (gas–liquid chromatography) to validate the method. In most cases extrapolations were within 10% of the experimental findings and safely within or close to the scatter of literature data.The method allows for example the safe estimation of the infinite dilution behavior as well as liquid and solid solubility of high boiling components in hydrocarbons from data for high boiling solvents usually determined easily by gas–liquid chromatography. Additionally, the newly developed combinatorial expression for infinite dilution data should be able to greatly improve other predictive mixture models, e.g. UNIFAC, mod. UNIFAC and COSMO-RS type models in the cases when large molecules in low molecular weight solvents are considered. This was verified for a larger number of experimental limiting activity coefficient data from literature.

Apparent molar volumes and compressibilities of electrolytes and ions in γ-butyrolactone

The densities of tetraphenylphosphonium bromide, sodium tetraphenylborate, lithium perchlorate, sodium perchlorate and lithium bromide in γ-butyrolactone at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15)K and speed of sound at 298.15K have been measured. From these data apparent molar volumes VΦ at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15)K and the apparent molar isentropic compressibility KS,Φ, at T=298.15K of the salts have been determined. The apparent molar volumes and the apparent molar isentropic compressibilities were fitted to the Redlich, Rosenfeld and Mayer equation as well as to the Pitzer and Masson equations yielding infinite dilution data. The obtained limiting values have been used to estimate the ionic data of the standard partial molar volume and the standard partial isentropic compressibility in γ-butyrolactone solutions.

Determination of infinite dilution activity coefficients using HS-SPME/GC/FID for hydrocarbons in furfural at temperatures of (298.15, 308.15, and 318.15) K

A new methodology using the headspace solid phase microextraction (HS-SPME) technique has been used to evaluate the infinite dilution activity coefficient (γ12∞) of nine hydrocarbons (alkanes, cycloalkanes, and aromatics) in furfural solvent. The main objective of this study was to validate a faster and lower cost methodology expanding the use of HS-SPME to determine infinite dilution activity of solutes in organic solvents. Two approaches were proposed for the determination of γ12∞ in order to use this technique (HS-SPME). In addition, the fiber–gas partition coefficients (Kfg) for each analyte at each of the studied temperatures were determined. The activity and partition coefficients have been reported at temperatures of (298.15, 308.15, and 318.15)K. The data were compared with the literature infinite dilution data determined by other methods such as liquid–gas chromatography (GLC) and gas stripping. Partial molar excess enthalpies of mixing at infinite dilution for each solute have been determined. The fibers were tested before and after each experiment, using statistical methods to ensure that their properties do not change during the experiments. The fibers were also analyzed by optical microscopy to evaluate possible surface damage by comparing them with new fibers. The activity coefficient values correlated well with the data in the literature and showed average deviations less than 10%.

Apparent molar volumes and compressibilities of tetrabutyl-ammonium bromide in organic solvents

The densities of tetra- n-butylammonium bromide in 1-propanol, 1-butanol, acetone at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and sound velocities at 298.15 K have been measured. From these data apparent molar volumes V Φ at (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 323.15) K and the apparent molar isenotropic compressibility K S , Φ , at T = 298.15 K of tetrabutylammonium bromide in nonaqueous solvents have been determined. The apparent molar volumes and the apparent molar isenotropic compressibilities were fitted to the Redlich, Rosenfeld, and Mayer equation as well as to the Pitzer equation yielding infinite dilution data, which were compared to the similar quantities for tetrabutylphosphonium bromide. Moreover, the acoustical parameters such as intermolecular free length ( L f ), relative association ( R A ), Rao’s molar sound function ( R m ), and salvation number ( S n ) were calculated using the experimental data of density and sound velocity at T = 298.15 K for ammonium and phosphonium bromides. The obtained data suggest the penetration of the acetone molecule within the intraionic free space of the tetrabutyl-ammonium and phosphonium cations.

Prediction of activity coefficients at infinite dilution for organic solutes in ionic liquids by artificial neural network

To our knowledge, this work illustrates for the first time the ability of artificial neural network (ANN) to predict activity coefficients at infinite dilution for organic solutes in ionic liquids (ILs). Activity coefficient at infinite dilution ( γ ∞) is a useful parameter which can be used for the selection of effective solvent in the separation processes. Using a multi-layer feed-forward network with Levenberg–Marquardt optimization algorithm, the resulting ANN model generated activity coefficient at infinite dilution data over a temperature range of 298 to 363 K. The unavailable input data concerning softness ( S) of organic compounds (solutes) and dipole moment ( μ) of ionic liquids were calculated using GAMESS suites of quantum chemistry programs. The resulting ANN model and its validation are based on the investigation of up to 24 structurally different organic compounds (alkanes, alkenes, alkynes, cycloalkanes, aromatics, and alcohols) in 16 common imidazolium-based ionic liquids, at different temperatures within the range of 298 to 363 K ( i.e. a total number of 914 γ Solute ∞ for each IL data point). The results show a satisfactory agreement between the predicted ANN and experimental data, where, the root mean square error (RMSE) and the determination coefficient ( R 2) of the designed neural network were found to be 0.103, 0.996 for training data and 0.128, 0.994 for testing data, respectively.

A new relation from the HSAB theory for predicting the conductivity maxima of salts in nonaqueous solvents

It is shown that not only the relative permittivity or the dynamic viscosity, but also the chemical nature of the salt and that of the solvent can be taken into account to predict the most important properties of electrolytes: the conductivity maximum κ MAX and the equivalent conductivity at infinite dilution Λ 0. For taking into account the chemical nature of the salt and of the solvent, we assumed that solvation reactions could be expressed in terms of the absolute chemical hardness of the salt, η ACH salt, and that of the solvent, η ACH solvent (or their absolute difference, ∣Δ η ACH∣). Relations are proposed for κ MAX and the equivalent conductivity at infinite dilution Λ 0. Their validity is supported by our own conductivity data and by equivalent conductivity at infinite dilution data from the literature for a wide range of different systems. The accuracy of our predictions seems to be ±20%.

A generalized correlation for Henry’s Law constants of nonpolar solutes in four polymers

In this work, Henry’s Law constants of nonpolar solutes in four polymers were obtained by extrapolation of finite concentration vapor–liquid equilibrium (VLE) data using the UNIQUAC equation to infinite dilution condition. The consistency of the results was confirmed by comparing them with infinite dilution data through the linear relationship between logarithm of Henry’s Law constants and inverse of temperatures. This verification provided good method for crosschecking a reliability of finite concentration VLE data with infinite dilution data. Henry’s Law constants were correlated based on both types of data as a function of temperature using the classical van’t Hoff equation. Generalized correlations of the Henry’s Law constants of solutes were proposed for polyisoprene (PI), polyisobutylene (PIB) and poly( n-butyl methacrylate) (PBMA).

The Modeling of Carbon Dioxide-Aided Extraction of Carboxylic Acids from Aqueous Solutions

Carbon dioxide (CO2)-aided acidification of aqueous carboxylate solutions and simultaneous reactive extraction of the carboxylic acid is a promising and clean alternative method for the conventional recovery of carboxylic acids. The complexity of the extraction system is endorsed by the presence of three or four coexisting phases (i.e., vapor−liquid−liquid−(solid)) and an aqueous electrolyte solution. Selection of optimal operating conditions in this complex four-phase system requires a robust, yet simple model for description of the phase equilibria. In this work, such a simple shortcut model is presented. Although the model parameters are obtained from pure component or infinite dilution data only, the model yields a reasonable description with experimental data. Model predictions were compared with experimental data for the CO2-aided extraction of lactic acid with two different amine extractants from various concentrations of a calcium lactate solution and pressures up to 3.1 MPa. The model is expected to be very useful for equipment and process design.

Molecular thermodynamics of solute‐polymer‐supercritical fluid systems

AbstractThe distribution coefficients of the solutes (toluene, naphthalene, and phenanthrene) are reported at infinite dilution between silicone rubber and supercriticalfluid carbon dioxide. A new technique is described in which a thin film of polymer is coated and cross‐linked onto silica, and the distribution coefficient is measured rapidly by elution supercritical‐fluid chromatography. Because CO2 significantly enhances the solute's volatility and its diffusion coefficient in the polymer, it is possible to study solute‐polymer interactions at room temperature for nonvolatile compounds which would be difficult to study by conventional techniques such as gas chromatography. These infinite dilution data are used to determine solutepolymer interaction parameters to calculate phase diagrams over a wide concentration range. The residual, combinatorial, and cross‐link contributions to the solute activity coefficient in the polymer are discussed as a function of concentration. In addition, pronounced pressure and temperature effects are described in terms of experimentally measured solute partial molar volumes (to – 14 L/mol) and partial molar enthalpies (to – 850 kJ/mol) in the fluid phase.

Calculation of multicomponent ionic diffusion from zero to high concentration: II. Inclusion of associated ion species

This paper presents a theoretical model of multicomponent ionic diffusion which is valid to high concentration for systems which show ion association. The development is completely general for species which do not react with the solvent. It is demonstrated that the Onsager phenomenological coefficients for associated ion species can be unambiguously determined only in solutions where the concentration of these species can be independently measured. In all other instances, only combinations of the Onsager coefficients for the bare ions and the ion pairs can be experimentally determined. The results of our formulations are contrasted with those of more simplified models for systems containing Na 2SO 4 and MgSO 4, as well as for multicomponent natural seawater. The differences between our model and simplified models are significant, especially at high concentration. Inconsistencies which may develop with the use of the simplified approaches are demonstrated. Our approach requires considerable data which are not available at temperatures other than 25°C. Therefore, other approaches which are based only on data at infinite dilution are of great interest. We show here that, if chemical potential derivatives are included in the infinite dilution model of Nernst and Hartley which uses only infinite dilution mobilities, the model can be extended to slightly concentrated solutions. This extended Nernst-Hartley model gives good agreement with all of the existing experimental mutual diffusion coefficient data at concentrations below about 0.2 M in the six component system Na-K-Ca-Mg-Cl-SO 4-H 2O. This may be the most reliable way to extend infinite dilution data into more concentrated regions. In the systems we have studied, the inclusion of ion-association species for weakly interacting species does not appear to provide significant improvement over our generalized Nernst-Hartley model.

K-values at essentially infinite dilution for carbon dioxide and hydrogen sulfide in the methane-n-octane system at low temperatures and elevated pressures

Vapor-liquid equilibrium data are needed for absorber calculations on natural gas systems to follow the distribution of naturally occurring nonhydrocarbon components. Infinite dilution data are useful not only for design calculations but also for the theoretical development of correlations. The data presented here are for the nonhydrocarbons carbon dioxide and hydrogen sulfide, each in the methane-n-octane system a t low temperature and high pressure.

The correlation of vapor‐liquid equilibria of light hydrocarbons in paraffinic and in aromatic solvents at low temperatures and elevated pressures

AbstractA correlational procedure was developed to predict the vapor liquid equilibrium behavior of light hydrocarbons in heavier hydrocarbon solvents at low temperatures and elevated pressures. The method is applicable to paraffinic as well as aromatic solvents.The method employed the Benedict‐Webb‐Rubin equation of state to predict the vapor phase fugacities. Methane liquid fugacities in the various hydrocarbon solvents were based upon Henry's law which included terms to account for compositional and pressure effects. The liquid fugacities for ethane and propane were calculated using infinite dilution data to modify empirically the Scatchard‐Hildebrand equation. Excellent agreement between the correlated and low‐temperature data available on this class of systems was obtained.

The study of multicomponent gas‐solid equilibrium at high pressures by gas chromatography: Part II. Generalization of the theory and application to the methane‐propane‐silica gel system

AbstractThe mathematical relation for the retention volume for elution chromatography has been extended to include the case of a multicomponent elution gas mixture in which all the components are adsorbed appreciably on the adsorbent. The total adsorption, component adsorption, and the K values or the ratio of the gas‐phase concentration to the adsorbed‐phase concentration for each component are related to the retention volume for the components as measured by a technique which distinguishes the molecules in the elution gas from those in the perturbing sample. Radioactively traced hydrocarbons are used in the application to obtain the retention volumes appropriate for the theory.The relations derived were applied in studying the adsorption of methane‐propane mixtures on silica gel up to a pressure of 1,000 lb./sq. in. abs. The internal consistency of the propane adsorption data with the propane infinite dilution data and the methane data with the pure methane adsorption data obtained by a gravimetric method is demonstrated.