Molar Excess Entropy Research Articles

Infinite dilution activity coefficients of volatile organic compounds in two ionic liquids composed of the tris(pentafluoroethyl)trifluorophosphate ([FAP]) anion and a functionalized cation

Interactions of volatile organic compounds with two ionic liquids (ILs) containing tris(pentafluoroethyl)trifluorophosphate ([FAP]) anion and a functionalized cation, 1-(2-hydroxyethyl)-3-methylimidazolium ([HO-EMIM]) and 1-(2-methoxyethyl)-1-methylpyrrolidinium ([MO-EMPYR]), were explored through systematic GLC retention measurements. Infinite dilution activity coefficients γ1∞ and gas–liquid partition coefficients KL of 30 selected solutes in [HO-EMIM][FAP] and [MO-EMPYR][FAP] 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 the KL values. The LFER correlation parameters and excess thermodynamic functions were analyzed to identify molecular interactions operating between the ILs and the individual solutes. By comparing the behaviors of the studied ILs and of their closely similar unfunctionalized analogs, net effects imparted by cation functionalization were also disclosed. The cohesivity of the two ILs was shown to differ dramatically: while [MO-EMPYR][FAP] ranks among ILs to the least cohesive, [HO-EMIM][FAP] belongs to the most cohesive ones. Both [HO-EMIM][FAP] and [MO-EMPYR][FAP] are capable of interacting with solutes specifically through dipolarity/polarizibility and hydrogen bonding, but apparently lack the ability to interact with solute lone electron pairs. The proton donating capability of [HO-EMIM][FAP], undoubtedly brought by the hydroxyl functionality, is enormous and imparts to this IL extraordinary potential for use in solvent-aided separations. As we have demonstrated on some model aliphatic/aromatic separation pairs, [HO-EMIM][FAP] as a solvent for the separation of aliphatic hydrocarbons from aromatics gives superior performance, its performance index (product of selectivity and capacity) surpassing distinctly that of conventional solvents and of most ILs studied so far. [HO-EMIM][FAP] and [MO-EMPYR][FAP] could also serve as efficient entrainers in separations of other non-petrochemical azeotropic systems of industrial importance by extractive distillation as exemplified for some mixtures of alcohols with aprotic oxygenates.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate

This work presents new data of activity coefficients at infinite dilution, γ∞ of different organic solutes and water in the 1-(2-hydroxyethyl)-3-methylimidazolium trifluorotris(perfluoroethyl)phosphate, [C2OHmim][FAP] ionic liquid. Values of γ∞ were determined for 65 organic solutes, including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, 1-nitropropane, aldehydes, acetonitrile and water by inverse gas chromatography within the temperature range from (318.15 to 368.15)K. The basic thermodynamic functions, such as partial molar excess Gibbs energies, ΔG1E,∞, enthalpies, ΔH1E,∞ and entropies, ΔS1E,∞ at infinite dilution were calculated from the experimental γ∞ values obtained over the temperature range. Additionally the gas–liquid partition coefficients, KL were determined. Experimental values of gas–liquid partition coefficients were used to determine the coefficients in the Abraham solvation parameter model (LFER). Results are compared to previously investigated ionic liquids with the same [C2OHmim]+ cation and [FAP]− anion. The selectivity and capacity at infinite dilution for alkanes/thiophene extraction problems were calculated from experimental γ∞ values to verify the possibility of investigated ionic liquid as an entrainer in liquid–liquid extraction.

Determination of the Mixing Thermodynamic Properties of Liquid Ternary Alloys by Fitting the Knudsen Effusion Mass Spectrometric Data to the Redlich-Kister-Muggianu Sub-Regular Solution Model

We discuss the vaporisation of four liquid ternary-alloy systems, namely, Cu-In-Sn, Ag-In-Sn, Al-Cu-Sn and Cu-Sb-Sn, on the basis of our previous Knudsen effusion mass spectrometric (KEMS) investigations of these systems. The thermodynamic activities and the thermodynamic functions (Gibbs energy, enthalpy, entropy) of mixing were determined using selected standard KEMS procedures (i.e., Simple Pressure Calibration Method (SPC), Oligomer Composition Change Method (OCC), Isothermal Evaporation Method (IEM) and Gibbs-Duhem Ion Intensity Ratio Method (GD-IIR)). In addition, the same thermodynamic quantities, as well as the so-called ternary interaction (L-) parameters, were also obtained from the composition dependence of the measured ion-intensity ratios using a new mathematical procedure (RKM-KEMS). The essence of this new procedure is the fitting of the measured intensity-ratio data were to the Redlich-Kister-Muggianu (RKM) sub-regular solution model, and this model is valid for many liquid ternary alloys, including the systems reviewed here. A full description of the mathematical derivation of RKM-KEMS is given in this work. The primary and intermediate data, obtained directly from the multiple-regression as output data, are the RKM ternary interaction L-parameters. From these quantities, the integral molar excess Gibbs energy, the excess chemical potentials, the activity coefficients and the activities were evaluated in this order. In addition, using the temperature dependence of activities, the integral and partial molar excess enthalpies and entropies could also be determined. The thermodynamic data obtained with the above-mentioned conventional KEMS methods and with the new RKM-KEMS procedure were compared and a good agreement was obtained for the systems studied.

Liquid phase PVTx properties of binary mixtures of (water + ethylene glycol) in the range from 278.15 to 323.15 K and from 0.1 to 100 MPa. I. Experimental results, partial and excess thermodynamics properties

The coefficient of compressibility, k=ΔV/Vo, of {water (1)+ethylene glycol (2)} binary mixture was measured at pressures from 0.1 to 100MPa and temperatures from 278.15 to 323.15K over the whole concentration range. At all state parameters the following characteristics were calculated: excess molar volumes of the mixture, VmE; changes of excess molar Gibbs energy, ΔPo→PGmE; changes of excess molar entropy, ΔPo→PSmE; changes of excess molar enthalpy, ΔPo→PHmE; mixing enthalpy, HmE, of water with ethylene glycol at high pressure, and partial molar volumes of the components. It was shown that the coefficients of compressibility, k, sharply decreased over the concentration interval x2=0–0.2, where x2 was ethylene glycol mole fraction, and further changed insignificantly. It was revealed that excess molar volumes were negative at all temperatures studied and went down with pressure increasing. The dependence of partial molar volumes of the mixture components on ethylene glycol mole fraction passes extreme at all isobars. Limiting partial molar volumes of water and ethylene glycol decrease with pressure growth. The mixture compression leads to its ordering due to new hydrogen bonds formation.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate

This work presents new data of activity coefficients at infinite dilution, γ∞ of different organic solutes and water in the 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate ionic liquid. Values of γ∞ were determined for 62 solutes, including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, 1-nitropropane, butanal, acetonitrile and water by inverse gas chromatography over the temperature range from (318.15 to 368.15)K. The basic thermodynamic functions, namely partial molar excess Gibbs energies, ΔG1E,∞, enthalpies, ΔH1E,∞ and entropies, ΔS1E,∞ at infinite dilution were calculated from the experimental γ∞ values obtained over the temperature range. Additionally the gas–liquid partition coefficients, KL were determined. Experimental values of gas–liquid partition coefficients were used to determine the coefficients in the Abraham solvation parameter model (LFER). Results are compared to previously investigated ionic liquids with the same cations or anions. The selectivities and capacities at infinite dilution for alkanes/thiophene extraction problems were calculated from experimental γ∞ values to verify the possibility of investigated ionic liquid as an entrainer in liquid–liquid extraction.

Activity coefficient at infinite dilution measurements for organic solutes (polar and non-polar) in fatty compounds – Part II: C18 fatty acids

In this work, activity coefficients at infinite dilution (γ13∞) have been measured for 21 solutes (subscript 1) (alkanes, cycloalkanes, alkenes, aromatic compounds, alcohols, esters, ketones, and halogenated hydrocarbons), in four solvents (subscript 3), namely one saturated fatty acid and three unsaturated fatty acids: stearic (octadecanoic) acid – C18:0, oleic (cis-9-octadecenoic) acid – C18:1 9c, linoleic (cis,cis-9,12-octadecadienoic) acid – C18:2 9c12c, and linolenic (cis,cis,cis-9,12,15-octadecatrienoic) acid – C18:3 9c12c15c, by gas–liquid chromatography. The measurements were carried out at temperatures from (303.13 to 368.19)K and the partial molar excess Gibbs free energy (ΔG1E,∞), enthalpy (ΔH1E,∞), and entropy (ΔS1E,∞), at infinite dilution were calculated from experimental γ13∞ values obtained over the temperature range. The uncertainties in determination of γ13∞ and ΔH1E,∞ are 4% and 20%, respectively. The results for stearic acid obtained in this study have been compared to those available in the Dortmund Data Bank (DDB). The real behaviour of fatty systems could be better understood through the results obtained in this work.

Infinite dilution partial molar excess entropy–enthalpy compensation for thiophene, carbon dioxide and water in ionic liquids

Infinite dilution partial molar excess entropy–enthalpy compensation for polar solutes in an ionic liquid (IL) is investigated using the literature data of infinite dilution activity coefficient, ln γ1∞. Entropy–enthalpy compensation holds for the polar solutes, such as thiophene and CO2, and non-polar solutes, such as heptane and toluene. For the water+IL binaries, a converged linear relationship between infinite dilution partial molar excess entropy and enthalpy holds. Using the compensation rule, it is shown that, for the efficient removal of thiophene and CO2 from non-polar solutes with IL solvents, ILs having weaker molecular interactions with thiophene and CO2 are advantageous, because the entropy terms control the ln γ1∞ values.

A macroscopic model that connects the molar excess entropy of a supercooled liquid near its glass transition temperature to its viscosity

For a deeply supercooled liquid near its glass transition temperature, we suggest a possible way to connect the temperature dependence of its molar excess entropy to that of its viscosity by constructing a macroscopic model, where the deeply supercooled liquid is assumed to be a mixture of solid-like and liquid-like micro regions. In this model, we assume that the mole fraction x of the liquid-like micro regions tends to zero as the temperature T of the liquid is decreased and extrapolated to a temperature T(g)(*), which we assume to be below but close to the lowest glass transition temperature T(g) attainable with the slowest possible cooling rate for the liquid. Without referring to any specific microscopic nature of the solid-like and liquid-like micro regions, we also assume that near T(g), the molar enthalpy of the solid-like micro regions is lower than that of the liquid-like micro regions. We then show that the temperature dependence of x is directly related to that of the molar excess entropy. Close to T(g), we assume that an activated motion of the solid-like micro regions controls the viscosity and that this activated motion is a collective motion involving practically all of the solid-like micro-regions so that the molar activation free energy Δg(a) for the activated motion is proportional to the mole fraction, 1 - x, of the solid-like micro regions. The temperature dependence of the viscosity is thus connected to that of the molar excess entropy s(e) through the temperature dependence of the mole fraction x. As an example, we apply our model to a class of glass formers for which s(e) at temperatures near T(g) is well approximated by s(e) ∝ 1 - T(K)∕T with T(K) < T(g) ≅ T(g)(*) and find their viscosities to be well approximated by the Vogel-Fulcher-Tamman equation for temperatures very close to T(g). We also find that a parameter a appearing in the temperature dependence of x for a glass former in this class is a measure for its fragility. As this class includes both fragile and strong glass formers, our model applies to both fragile and strong glass formers. We estimate the values of three parameters in our model for three glass formers in this class, o-terphenyl, 3-bromopentane, and Pd(40)Ni(40)P(20), which is the least fragile among these three. Finally, we also suggest a way to test our assumption about the solid-like and liquid-like micro regions by means of molecular dynamics simulations of model liquids.

Physicochemical properties and activity coefficients at infinite dilution for organic solutes and water in a novel bicyclic guanidinium superbase-derived protic ionic liquid

The activity coefficient at infinite dilution, γ13∞, was determined by gas–liquid chromatography at temperatures from T=308.15 to T=348.15K for 54 assorted solutes—among them, alkanes (linear, branched, or cyclic), alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, tetrahydrofuran, 1,4-dioxane, ethers, acetone, ketones, acetonitrile, pyridine, and 1-nitropropane—in the novel bicyclic guanidine superbase-derived protic ionic liquid 1,3,4,6,7,8-hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine bis(pentafluoroethyl)sulfonylimide, [MTBDH][BETI]. The partial molar excess Gibbs free energy ΔG1E,∞, the partial molar excess enthalpy ΔH1E,∞, and entropy at reference temperature TrefΔS1E,∞ at infinite dilution were calculated from the experimental γ13∞ values obtained over this temperature range. The gas–liquid partition coefficient, KL, was calculated for each solute and discussed in light of the Abraham solvation parameter model. The density of the IL as a function of temperature was also measured. The selectivities for heptane/benzene, heptane/thiophene, heptane/pyridine, and heptane/nitropropane separation problems were calculated from γ13∞ and compared to literature values for select ILs, as these separation problems are central to the petroleum industry.

Interactions of volatile organic compounds with the ionic liquids 1-butyl-1-methylpyrrolidinium tetracyanoborate and 1-butyl-1-methylpyrrolidinium bis(oxalato)borate

Interactions of volatile organic compounds with two ionic liquids (ILs) 1-butyl-1-methylpyrrolidinium tetracyanoborate [BMPYR][B(CN)4] and 1-butyl-1-methylpyrrolidinium bis(oxalato)borate [BMPYR][BOB] were explored through systematic GLC retention measurements. Infinite dilution activity coefficients γ1∞ and gas–liquid partition coefficients KL of 30 selected solutes in [BMPYR][B(CN)4] and [BMPYR][BOB] were determined at five temperatures in the range from (318.15 to 353.15)K and from (333.15 to 373.15)K, respectively. 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 ILs and the individual solutes. Among other ILs, [BMPYR][B(CN)4] was identified as a very weakly cohesive solvent medium, in contrast to [BMPYR][BOB] which appears to be fairly cohesive IL close in this respect to [BMPYR][DCA] examined recently. Both [BMPYR][B(CN)4] and [BMPYR][BOB] are capable of interacting specifically through all modes (lone electron pairs, dipolarity/polarizibility, and hydrogen bonding) with solutes of complementary capabilities. Their hydrogen bond basicity and ability to interact with lone electron pairs are appreciable but distinctly lower than those of [BMPYR][DCA]. The proton donating capability of these ILs is weak, but still traceable, and stems undoubtedly from unsubstituted hydrogen atoms on the pyrrolidinium ring of their cation. The selectivities of [BMPYR][B(CN)4] and [BMPYR][BOB] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons rank among [BMPYR] ILs the lowest and medium, respectively. The selectivity of [BMPYR][B(CN)4] is comparable to that of sulfolane, but this IL surpasses it roughly three times in the capacity. [BMPYR][B(CN)4] and [BMPYR][BOB] could also serve as efficient entrainers in separations of other non-petrochemical azeotropic systems of industrial importance by extractive distillation. In particular, we have identified [BMPYR][B(CN)4] as a very convenient separation agent for (methanol+dimethyl carbonate) mixture.

Activity coefficients at infinite dilution and physicochemical properties for organic solutes and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpiperidinium trifluorotris(perfluoroethyl)phosphate

This work is continuation of our systematic study of activity coefficients at infinite dilution, γ∞ of different organic solutes and water in the ionic liquids. New data of γ∞ were determined for 62 solutes, including alkanes, alkenes, alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, 1-nitropropane, butanal, acetonitrile, and water in the ionic liquid 1-(2-methoxyethyl)-1-methylpiperidinium trifluorotris(perfluoroethyl)phosphate by inverse gas chromatography at the temperature range from (318.15 to 368.15)K. The basic thermodynamic functions, namely partial molar excess Gibbs free energies, ΔG1E,∞, enthalpies, ΔH1E,∞ and entropies, ΔS1E,∞ at infinite dilution were calculated from the experimental γ∞ values obtained over the temperature range. Additionally the gas–liquid partition coefficients, KL were determined. Results are compared to previously investigated ionic liquids with the same cations or anions. Values of the selectivity and capacity at infinite dilution for heptane/benzene, heptane/thiophene, and heptane/methanol extraction problems were calculated from experimental γ∞ values to verify the possibility of investigated ionic liquid as an entrainer in liquid–liquid extraction.

Activity coefficient at infinite dilution measurements for organic solutes (polar and non-polar) in fatty compounds: Saturated fatty acids

The activity coefficients at infinite dilution , γ13∞ (the subscript 1 and 3 correspond to solute and solvent, respectively), for 21 solutes, including alkane, cycloalkane, alkene, aromatic compounds, alcohol, ester, ketone, and halogenated hydrocarbons, in four solvents, that are the saturated fatty acids: capric (decanoic) acid, lauric (dodecanoic) acid, myristic (tetradecanoic) acid, and palmitic (hexadecanoic) acid, were determined by gas–liquid chromatography at temperatures from 314.10K to 358.33K. Comparison with previously published for selected solutes in palmitic (hexadecanoic) acid were also performed. The values of the partial molar excess Gibbs free energy, ΔG13∞, enthalpy, ΔH13∞, and entropy, ΔS13∞, at infinite dilution were calculated from experimental γ13∞ values obtained over the temperature range. Results obtained in this work allow a more accurate description of the real behavior of fatty systems.

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.

Experimental evidence for excess entropy discontinuities in glass-forming solutions

Glass transition temperatures T(g) are investigated in aqueous binary and multi-component solutions consisting of citric acid, calcium nitrate (Ca(NO(3))(2)), malonic acid, raffinose, and ammonium bisulfate (NH(4)HSO(4)) using a differential scanning calorimeter. Based on measured glass transition temperatures of binary aqueous mixtures and fitted binary coefficients, the T(g) of multi-component systems can be predicted using mixing rules. However, the experimentally observed T(g) in multi-component solutions show considerable deviations from two theoretical approaches considered. The deviations from these predictions are explained in terms of the molar excess mixing entropy difference between the supercooled liquid and glassy state at T(g). The multi-component mixtures involve contributions to these excess mixing entropies that the mixing rules do not take into account.

Enhancing tracer diffusivity by tuning interparticle interactions and coordination shell structure

This study uses a combination of stochastic optimization, statistical mechanical theory, and molecular simulation to test the extent to which the long-time dynamics of a single tracer particle can be enhanced by rationally modifying its interactions--and hence static correlations--with the other particles of a dense fluid. Specifically, a simulated annealing strategy is introduced that, when coupled with test-particle calculations from an accurate density functional theory, finds interactions that maximize either the tracer's partial molar excess entropy or a related pair-correlation measure (i.e., two quantities known to correlate with tracer diffusivity in other contexts). The optimized interactions have soft, Yukawa-like repulsions, which extend beyond the hard-sphere interaction and disrupt the coordination-shell cage structure surrounding the tracer. Molecular and Brownian dynamics simulations find that tracers with these additional soft repulsions can diffuse more than three times faster than bare hard spheres in a moderately supercooled fluid, despite the fact that the former appear considerably larger than the latter by conventional definitions of particle size.

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.

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...

Density, Viscosity, Vapor−Liquid Equilibrium, and Excess Molar Enthalpy of [Chloroform + Methyl tert-Butyl Ether

Density and viscosity measurements in the T = (273.15 to 318.15) K range of pure chloroform and methyl tert-butyl ether (MTBE), as well as of the binary system [x1 chloroform + (1 − x1) MTBE] over the whole concentration range at T = 293.15 K, were made. The experimental results for the pure components were fitted to empirical equations, which permit the calculation of these properties in the studied temperature range. Calculated values are in agreement with the experimental ones. Data of the binary mixture were further used to calculate the excess molar volume and viscosity deviations. The excess molar enthalpy at T = (303 ± 1) K and vapor−liquid equilibrium measurements at T = (303.15 ± 0.05) K were also measured for the binary system. These last experimental results were used to calculate activity coefficients, the excess molar Gibbs energy, and excess molar entropy. This binary system shows strong negative deviations from ideality and exhibits a minimum pressure azeotrope, whose coordinates are: P = (...

Activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium methanesulfonate

Infinite dilution activity coefficients γ 1 ∞ and gas–liquid partition coefficients K L of 30 selected hydrocarbons, alcohols, ketones, ethers, esters, haloalkanes, nitrogen- and sulphur-containing compounds in the ionic liquid (IL) 1-ethyl-3-methylimidazolium methanesulfonate [EMIM][MeSO 3] were determined by gas–liquid chromatography at five temperatures in the range from 318.15 to 353.15 K. Relative contribution of adsorption at gas–liquid interphase to the overall solute retention, as examined by varying sample size and IL loading in the column, was found negligible. Partial molar excess enthalpies and entropies at infinite dilution were derived from the temperature dependence of the γ 1 ∞ values. The linear free energy relationship (LFER) solvation model was used to correlate successfully the K L values. The LFER correlation parameters and excess thermodynamic functions were analyzed to disclose molecular interactions operating between the IL and the individual solutes. Comparison to [EMIM][NO 3] studied previously revealed [MeSO 3] − anion to have still greater hydrogen bond basicity than that found for [NO 3] −. In addition, similarly to [EMIM][NO 3], promising potential of [EMIM][MeSO 3] for applications in solvent-aided separation processes was identified, the selectivities of [EMIM][MeSO 3] for separation of aromatic hydrocarbons and thiophene from saturated hydrocarbons ranking among the highest ever observed with ILs or molecular solvents.