Partial Molar Excess Enthalpies Research Articles

Activity coefficients at infinite dilution of organic solutes in 1-octyl-3-methylimidazolium nitrate using gas–liquid chromatography

Activity coefficients at infinite dilution and gas–liquid partition coefficients (KL) of 25 organic solutes, including alkanes, alkenes, alkylbenzenes, alcohols, acetonitrile, ethyacetate, acetone, tetrahydrofuran, dichloromethane, trichromethane, and tetrchloromrthane in the ionic liquid 1-octyl-3-methylimidazolium nitrate ([OMIM][NO3]), have been determined by means of gas–liquid chromatography over a temperature range of 303.15–363.15K with the ionic liquid as the stationary phase. From the dependence of experimental activity coefficients, the partial molar excess enthalpies at infinite dilution and the solubility parameters of the organic solutes in the ionic liquid [OMIM][NO3] have been determined.

Thermal and Volumetric Properties of Four Aqueous Aroma Compounds at Infinite Dilution

Mixing enthalpies and densities of highly dilute aqueous solutions of four aroma compounds (propyl acetate, methyl butyrate, 2,3-butanedione, and cis-3-hexen-1-ol) were measured as a function of solution composition at several temperatures in the range from (288.15 to 318.15) K using a recently described tandem flow arrangement of isothermal mixing microcalorimeter and vibrating-tube densimeter. The dissolution of all of the aroma compounds in water is strongly exothermic and accompanied with volume contraction. Based on the measured data, reliable values of infinite dilution partial molar excess enthalpy H1E,∞, partial molar volume V1∞, and partial molar excess volume V1E,∞ of the studied solutes at infinite dilution in water were determined. A comparison to literature data is possible only for some of our results for esters and indicates excellent agreement. Thanks to the high precision of our measurements, the temperature derivative properties, that is, infinite dilution partial molar excess heat ca...

Activity coefficients at infinite dilution of organic solutes in the ionic liquid ethyl(2-hydroxyethyl)dimethyl-ammonium diethylphosphate using gas–liquid chromatography

The activity coefficients at infinite dilution, γi∞, of 22 organic solutes in the ionic liquid ethyl(2-hydroxyethyl)dimethyl-ammonium diethylphosphate have been determined using gas–liquid chromatography at the temperatures ranging from 323.15 to 363.15K. The partial molar excess enthalpies at infinite dilution, HiE,∞, of the solutes in the ionic liquid were calculated from the temperature dependence of the experimental γi∞ values. The selectivity for the hexane/benzene and cyclohexane/benzene separation problems were also derived from γi∞ and compared to the literature values for other ionic liquids and N-methyl-2-pyrrolidone.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-amide

The activity coefficients at infinite dilution, γ∞, gas–liquid partition coefficients, KL, the partial molar excess Gibbs free energy ΔG1E,∞, enthalpy ΔH1E,∞ and entropy ΔS1E,∞ at infinite dilution for 61 organic solutes and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)-amide were determined by inverse gas chromatography at the temperatures from (318.15 to 368.15)K. The values of the selectivity for selected compounds which form azeotropic mixtures were calculated from the γ∞ and compared to the literature values for other ionic liquids based on bis(trifluoromethylsulfonyl)-amide anion.

Measurements of activity coefficients at infinite dilution for organic solutes and water in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate

The activity coefficients at infinite dilution, γ13∞, for 43 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, acetonitrile, pyridine, and 1-nitropropane in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO3] were determined by gas–liquid chromatography at six temperatures within the range (308.15 to 358.15)K. The interaction of these 42 organic compounds and water with the ionic liquid were described with the partial molar excess Gibbs free energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy TrefΔS1E,∞ at infinite dilution, calculated from the experimental γ13∞ values obtained over the temperature range. The gas–liquid partition coefficients, KL were calculated for all solutes. The values of the selectivity for few separation problems as heptane/toluene, cyclohexane/benzene, heptane/xylenes and heptane/thiophene were calculated from γ13∞ and compared to literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and other ionic liquids based on [EMIM]+ cation. Comparison with the results published earlier for [EMIM][MeSO3] show much lower selectivities in the discussed separation problems. By contrast with the former measured ILs [EMIM][MeSO3] reveals the average selectivity for the separation of aromatics/aliphatics and low capacity for benzene. An interesting high value of selectivity was observed in the separation of thiophene/aliphatics. Very high values of selectivity may be expected in the separation of the azeotropic systems including water. The density of [EMIM][MeSO3] within temperature range from (298.15 to 358.15)K was measured and compared to the literature values.

Probing Thermal Interactions of Ionic Liquids with Dimethyl Sulfoxide

Interactions between ionic liquids and dimethyl sulfoxide (DMSO) are probed by isothermal titration calorimetry. The excess partial molar enthalpies of ionic liquids H(IL)(E) in DMSO are discussed in terms of solute-solvent interactions. The specific interaction theory originally developed by Pitzer is used to analyze the apparent molar enthalpy φ(L) of ionic liquids in DMSO with the help of ion-interaction parameters. Furthermore, quantitative information on solvent reorganization and clathrate formation is obtained and interpreted.

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%.

Activity coefficients at infinite dilution of organic solutes in the ionic liquid trihexyltetradecylphosphonium hexafluorophosphate using gas–liquid chromatography at T = (313.15, 333.15, 353.15, and 363.15) K

Activity coefficients at infinite dilution γ13∞ for 31 organic solutes (n-alkanes, alk-1-enes, alk-1-ynes, cycloalkanes, alkylbenzenes, alcohols, and ketones) in the ionic liquid trihexyltetradecylphosphonium hexafluorophosphate [3C6C14P][PF6] were determined by gas–liquid chromatography at T=(313.15, 333.15, 353.15, and 363.15)K. From experimental values, the partial molar excess enthalpy values at infinite dilution, ΔH1E,∞, together with the selectivity, Sij∞, and the capacity, kj∞, (which are related to the separation of liquids) were calculated and compared to literature values for other ionic liquids, as well as industrial solvents.

Vapor-Phase Mole Fractions Determined from the P, x Data Using the Margules Equation for High-Pressure Binary Vapor–Liquid Equilibrium Systems Including Carbon Dioxide

High-pressure P, x data for CO2 + hydrocarbons, methanol, ethanol, and water binaries were correlated using the Margules equation. The average relative difference between experimental data and the correlation was as low as 1 % at T < Tc1, where T and Tc1 denote the system temperature and the critical temperature of the lighter component. It was found that the average relative difference of the vapor phase mole fractions from the Margules equation representing the P, x data is 0.6 % for the asymmetric and nonazeotropic binaries. A criterion for identifying the nonazeotropic binaries is proposed. The strength of molecular interactions and molecular order were identified for the azeotropic and zeotropic mixtures using partial molar excess enthalpies and entropies at infinite dilution. A method for the high-precision correlation of infinite dilution activity coefficients is proposed.

Thermodynamic Study of Heptane + Silicone Mixtures. Excess Volumes and Enthalpies at 298.15 K

Excess molar volumes VE and partial molar enthalpies and excess enthalpies HE of binary mixtures of heptane + linear (hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamet...

Interactions of Volatile Organic Compounds with the Ionic Liquid 1-Butyl-1-methylpyrrolidinium Dicyanamide

Interactions of volatile organic compounds with the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium dicyanamide [BMPYR][DCA] were explored through systematic gas–liquid chromatography retention measurements. Infinite dilution activity coefficients γ1∞ and gas–liquid partition coefficients KL of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, and nitrogen- or sulfur-containing compounds in [BMPYR][DCA] were determined at five temperatures in the range from (318.15 to 353.15) K. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the γ1∞ values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. Among other ILs, [BMPYR][DCA] was identified to be a fairly cohesive solvent medium, which is capable o...

Activity Coefficients at Infinite Dilution by GLC in Alkanediamines as Stationary Phases

The infinite-dilution activity coefficients (γ∞) of paraffins, olefins, chloroparaffins, aromatics, alcohols, ethers, and acetates were measured by medium-pressure gas–liquid chromatography (GLC) in alkanediamines: octane-1,8-diamine, decane-1,10-diamine, and dodecane-1,12-diamine at temperatures from (328.15 to 363.15) K. The present measurements show good agreement with available literature data. The partial molar excess enthalpies at infinite dilution, ΔHiE,∞, were calculated from the experimental γi∞ values obtained over the temperature range. In order to determine the different interactions between the solutes and solvents, the linear solvation energy relationship (LSER) or “Abraham method” was applied.

Activity Coefficients of Organic Solutes at Infinite Dilution in Ionic Liquids. 1. 1-Hexyl-3-Methylimidazolium Hexafluorophosphate and 1-Octyl-3-Methylimidazolium Hexafluorophosphate and Their Application to Alkane/Aromatic and Aromatic/Aromatic Hydrocarbon Separation

Activity coefficients at infinite dilution, γi,3∞, for organic solutes (alkanes, alkenes, alkyl benzenes, alcohols, chloromethanes, acetonitrile, ethyl acetate, dioxane, tetrahydrofuran, and acetone) in 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF6] and 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM][PF6] have been determined using gas–liquid chromatography at temperatures from 303.15 to 363.15 K with the ionic liquids as the stationary phase. The partial molar excess enthalpies at infinite dilution of the ionic liquids were calculated for the solutes from the temperature dependence of the experimental activity coefficients at infinite dilution. The solubility parameters of ionic liquids were also determined by the regular solution theory. The selectivities of various ionic liquids for the alkane/aromatic hydrocarbon and aromatic/aromatic were summarized from literature and calculated from γi,3∞.

Correlation of calorimetric data of isoamyl acetate plus primary and secondary alcohols (C 1–C 4) by Redlich–Kister, NRTL and UNIQUAC models at 298.15 K

Calorimetric measurements were performed for six binary mixtures of isoamyl acetate + alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol and 2-butanol) by a Parr 1455 solution calorimeter over the entire composition range at T = 298.15 K and atmospheric pressure. The results were applied to calculate excess molar enthalpies H m E and excess partial molar enthalpies H i E . The H m E values were positive over the whole of composition range and become more positive with increasing the chain length and steric hindrance of the alkanols. The trend of the H m E data was interpreted in terms of the self-association of pure alkanols, dipole–dipole interactions between ester molecules and cross-association between unlike molecules (ester–alkanol). The correlations of experimental data were performed by Redlich–Kister equation and NRTL and UNIQUAC models.

Solubilities of Tris(o-phenylenedioxy)cyclotriphosphazene in Selected Solvents

Tris-(o-phenylenedioxy)-cyclotriphosphazene (TPP) was synthesized and characterized by elemental analysis (EA) and nuclear magnetic resonance (NMR). The melting point and the enthalpy of fusion of TPP were measured by da ifferential scanning calorimeter (DSC), and the thermal stability of TPP was measured by thermogravimetric analysis (TGA). Using a static analytical method, the solubility data of TPP in nine solvents were measured and correlated with an empirical equation. Moreover, using the Scatchard–Hildebrand model, activity coefficients have also been calculated and compared with the experimental values. The partial molar excess enthalpies at infinite dilution were also predicted.

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n=2 to 10), on the mixing properties of (ionic liquid+alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n=2 to 6 and then decreasing from n=8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2]+alcohol} binary mixtures at T=298K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

Limiting Activity Coefficients and Gas–Liquid Partition Coefficients of Various Solutes in Piperidinium Ionic Liquids: Measurements and LSER Calculations

This paper is a continuation of our systematic investigations on piperidinium ionic liquids and presents new data on activity coefficients at infinite dilution for 43 solutes: linear and branched alkanes, cycloalkanes, alkenes, alkynes, benzene, alkylbenzenes, alcohols, water, thiophene, tetrahyrdofuran (THF), methyl tert-butyl ether (MTBE), linear ethers, acetone, and linear ketones in the ionic liquid 1-butyl-1-methyl-piperidinium bis(trifluoromethylsulfonyl)imide, [BMPIP][NTf2]. The data were determined by gas-liquid chromatography (GLC) at temperatures from 308.15 to 358.15 K. These values were compared to those previously published for the bis-(trifluoromethylsulfonyl)imide-based ionic liquids. The partial molar excess enthalpies ΔH1(E,∞) and entropies ΔS1(E,∞) at infinite dilution were calculated from the experimental γ13(∞) values obtained over the temperature range. The values of the selectivities for different separation problems were calculated from γ13(∞) and compared to literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and additional ionic liquids. Experimental limiting activity coefficients were used to calculate gas-IL partition coefficients of solutes, K(L). The modeling with specific linear solvation energy relationship (LSER) equations was performed for data obtained in this work and those reported earlier for 1-butyl-1-methylpiperidinium thiocyanate, [BMPIP][SCN].

Determination of Infinite Dilution Partial Molar Excess Enthalpies and Volumes for Some Ionic Liquid Precursors in Water and Methanol Using Tandem Flow Mixing Calorimetry and Vibrating-Tube Densimetry

A flow mixing microcalorimetric system we developed recently was appended in this work with a vibrating tube densimeter into a tandem flow arrangement. This new combined apparatus (calo/densimeter) allows simultaneous automatic measurement of mixing enthalpies and densities of highly dilute solutions as a function of composition and, in turn, reliable determination of the solute's infinite dilution partial molar excess enthalpies H̅1E,∞ and volumes V̅1E,∞. The performance of the calo/densimeter was verified using 1-propanol in water, and then the apparatus was employed to determine H̅1E,∞ and V̅1E,∞ of several ionic liquid precursors (N-methylimidazole, N-methylpiperidine, N-methylmorpholine, 2-picoline, 3-picoline, and 2,6-lutidine) in water and methanol at 298.15 K. The changes of enthalpy associated with solvation and the transfer of the solutes from water to methanol were evaluated. The thermodynamic behavior observed for individual solutes was compared and briefly discussed in terms of molecular interactions.

Application of the extended real associated solution (ERAS) theory to excess molar enthalpies of benzaldehyde + 1-alkanols (C1 to C5) at T = 298.15 K

This paper reports excess molar enthalpies, HmE, for the binary mixtures of {1-alkanols (2), namely, {methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol} with benzaldehyde (1)} at T=298.15K at ambient pressure over a whole range of mole fraction. The sign of HmE for all systems are positive and the magnitude of HmE values with increasing of chain length, increase. The Redlich–Kister polynomial equation was used to correlate HmE. The excess partial molar enthalpies of benzaldehyde, Hm,1E, excess partial molar enthalpies of 1-alkanols (C1 to C5), Hm,2E, and excess partial molar enthalpies at infinite dilution, Hm,iE,0, are calculated according to experimental excess molar enthalpies and Redlich–Kister polynomial equation. The extracted date were used to evaluated the so-called intermolecular interaction functions ∂Hm,iE/∂xi and ∂Hm,iE/∂xj in terms of enthalpy. The ERAS, Wilson and NRTL models have been applied for describing the HmE.

Activity Coefficients at Infinite Dilution of Organic Solutes in 1-Butyl-3-methylimidazolium Nitrate Using Gas−Liquid Chromatography

Activity coefficients at infinite dilution of 21 organic solutes in the ionic liquid 1-butyl-3-methylimidazolium nitrate ([BMIM][NO3]) have been determined using gas−liquid chromatography over a temperature range of (303.15 to 363.15) K with the ionic liquid as the stationary phase. The partial molar excess enthalpies at infinite dilution and the solubility parameters of ionic liquid were determined for the solutes from the temperature dependence of the experimental activity coefficient at infinite dilution values.