Molar Excess Entropy Research Articles

Thermodynamic Assessment of Molten Bix-Sn1-x (x = 0.1 to 0.9) Alloys and Microstructural Characterization of Some Bi-Sn Solder Alloys.

Properties such as lower melting temperature, good tensile strength, good reliability, and well creep resistance, together with low production cost, make the system Bi-Sn an ideal candidate for fine soldering in applications such as reballing or reflow. The first objective of the work was to determine the thermodynamic quantities of Bi and Sn using the electromotive force measurement method in an electrolytic cell (Gibbs' enthalpies of the mixture, integral molar entropies, and the integral molar excess entropies were determined) at temperatures of 600 K and 903 K. The second objective addressed is the comprehensive characterization of three alloy compositions that were selected and elaborated, namely Bi25Sn75, Bi50Sn50, and Bi75Sn25, and morphological and structural investigations were carried out on them. Optical microscopy and SEM-EDS characterization revealed significant changes in the structure of the elaborated alloys, with all phases being uniformly distributed in the Bi50Sn50 and Bi75Sn25 alloys. These observations were confirmed by XRD and EDP-XRFS analyses. Diffractometric analysis reveals the prevalence of metallic Bi and traces of Sn, the formation of the Sn0.3Bi0.7, Sn0.95Bi0.05 compounds, and SnO and SnO2 phases.

Local composition-regular solution theory for analysis of pharmaceutical solubility in mixed-solvents

Local composition regular solution theory (LC-RST) model was developed by introducing non-equal i–j and j–i parameters into regular solution theory (RST) to account for specific molecular interactions. The LC-RST model was applied to the correlation of solubilities of active pharmaceutical ingredients (API) in hydrogen bond donor (HBD) – hydrogen bond acceptor (HBA) mixed-solvent systems. In the assessment of 32 API-mixed-solvent systems that contained 11 different APIs and 1947 data, it was determined that the LC-RST model had a logarithmic average relative deviation (ARDln) in solubility of 0.028, the Wilson model had an ARDln value of 0.24 and the purely predictive RST model had an ARDln value of 1.29. Partial molar excess enthalpies and entropies of the API in the mixed-solvents determined from the LC-RST model allowed estimation of API solubility regions where specific interactions occur between API and HBD-HBA complex molecules. In the correlation scheme, component numbers were designated as API molecule (1) – HBD molecule (2) - HBA molecule (3) and systems were grouped according to HBD molecule interactions with the API (pro-solvent, anti-solvent, synergistic with HBA molecule). Phenomenological parameter sensitivity analysis of the LC-RST model showed that dominant specific interactions tended to be 1–2 or 2–1 molecules for pro-solvent groupings, 2–3 or 2–3 molecules for anti-solvent groupings and all i–j and j-–i molecular pairs for synergistic HBD-HBA molecule groupings. Based on parameters determined from a given API-mixed-solvent system, the LC-RST model allows qualitative prediction of solubilities for other systems. The LC-RST model is simple to apply and it retains inherent predictive characteristics of regular solution theory.

Volumetric and viscometric properties of aqueous 1,2-dimethylethylenediamine solution for carbon capture application

The present work investigates the volumetric and viscometric properties of an aqueous solution of 1,2-dimethylethylenediamine (DEEDA) over an entire concentration range and an absorber operating temperature range of 313.15K–333.15K at atmospheric pressure. The investigated volumetric properties included the density, excess molar volume, partial molar volume, and the investigated viscometric properties included the viscosity, viscosity deviation, free energy for activation of viscous flow, excess free energy for activation of viscous flow, and excess entropy for activation of viscous flow. The results indicated that there are strong intermolecular interactions and suitable molecular packing in the binary DEEDA–water mixture. Hence, the mixture was found to deviate from a real mixture according to the calculated excess properties. The DEEDA solvent's preliminary volumetric and viscometric properties revealed convincing potential as a novel amine for carbon capture. Additionally, the Redlich-Kister-based correlations showed favorable correlative performance for excess molar volume, viscosity deviation, and excess entropy for activation of viscous flow.

Infinite Dilution Activity Coefficients and Gas–Liquid Partition Coefficients of Organic Compounds in Ionic Liquid 1-Butyl-2,3-dimethylimidazolium Thiocyanate: Measurements and LFER Calculations

Infinite dilution activity coefficients (γi∞) of 31 organic solutes (alkanes, cycloalkanes, olefins, aromatics, chlorinated alkanes, alcohols, and other polar organic solutes) in the ionic liquid (IL) 1-butyl-2,3-dimethylimidazole thiocyanate ([BMMIM][SCN]) were determined by gas–liquid chromatographic (GLC) method in the temperature range of 313.15–353.15 K. The infinite dilution partial molar excess enthalpies (H̅iE, ∞), entropies (TrefS̅iE, ∞), and Gibbs free energies (G̅iE, ∞) of the organic solutes at the reference temperature T = 298.15 K and the solubility parameters (δ3) of [BMMIM][SCN] were derived from γi∞. The gas–liquid partition coefficients (KL) of solutes at different temperatures were calculated by referring to the densities of [BMMIM][SCN]. The linear free energy relationship solvation model was used to fit the KL values, and the KL prediction model was obtained. The selectivity (Sij∞) and capacity (kj∞) of n-hexane (i)/benzene (j) and cyclohexane (i)/benzene (j) at infinite dilution at 323.15 K were calculated. The results were compared with the values of ILs with the thiocyanate anion in the literature.

Interfacial tension of carbon dioxide - water under conditions of CO2 geological storage and enhanced geothermal systems: A molecular dynamics study on the effect of temperature

In recent years, CO2 injection into geological formations under a wide range of temperature conditions, including super-hot geothermal reservoirs, has attracted much attention (i.e., higher than 500 K). Despite the importance, however, no study has been reported on the interfacial tension (IFT) of CO2 - water systems at temperatures higher than 478 K. In this study, we performed molecular dynamics (MD) simulations to estimate the CO2 - water IFT from 278 to 573 K at 8 to 50 MPa. Our results show the IFT at 10 MPa and 573 K is approximately 80% lower than that at a typical reservoir condition for CO2 geological storage. This indicates that the effect of the capillary pressure on the flow of CO2 and water in the geological formation is expected to be significantly reduced in such a super-hot geothermal reservoir.We discuss a possible mechanism for the IFT variation against temperature, including the maxima around 373 K at 8 to 12 MPa, which is reproduced and tackled by MD simulations for the first time. On the basis of the Gibbs-Duhem relation, the temperature dependence is directly related to the interfacial excess molar entropy. Our analyses show (1) the IFT increase is attributed to the substantial variation of the entropy and density of the bulk CO2 phase near the critical point, and (2) this variation is characterized by the distinct behavior of the molecular ordering and the mobility of CO2 at the interface, consistent with the close relationship between the disorder in molecular arrangement and configurational entropy.

Measurements and correlation of activity coefficients at infinite dilution for organic solutes in 1-heptyl-3-methylimidazolium chloride

This work is a continuation of our studies on the determination of activity coefficients at infinite dilution (γi∞) for organic solutes (i) in ionic liquids (ILs) and their use in separation processes. The values of γi∞ for 31 organic solutes including alkanes, cycloalkanes, 1,4-dioxane, aromatic hydrocarbons, cyclohexene, chloromethanes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate and alcohols in the IL 1-heptyl-3-methylimidazolium chloride ([C7MIm]Cl) at six temperatures in range of (313.15–363.15) K were determined by gas-liquid chromatography (GLC). The density of [C7MIm]Cl as a function of temperature at pressure p= 101.33 kPa was measured and the values of gas-liquid partition coefficients (KL) were obtained. The linear relationship between lnγi∞ and 1/T was fitted by the Gibbs-Helmholtz equation. The molar excess thermodynamic functions including the infinite dilution partial molar excess Gibbs free energies (G¯iE,∞), partial molar excess enthalpies (H¯iE,∞) and entropies (TrefS¯iE,∞) at Tref = 298.15 K were calculated. In addition, the solubility parameters (δi) of [C7MIm]Cl were obtained from the regular solution theory combined with Flory “combinatorial” equation. The interaction between the solute and the IL was quantified based on the linear free energy relationship (LFER) model. The infinite dilution selectivity coefficients (Sij∞) of n-hexane (i)/benzene (j) and cyclohexane (i)/benzene (j) were calculated at T = 323.15 K from γi∞ and compared to literature values for [Cl]-based ILs for the same separation problems.

Thermodynamics of trimethyltetradecylammonium bromide – Sodium deoxycholate binary mixed micelle formation in aqueous solution: Regular solution theory with mutual compensation of excess configurational and excess conformational entropy

A binary mixture of trimethyl(tetradecyl)ammonium bromide = TB-SD = sodium deoxycholate surfactants forms non-ideal binary mixed micelles that have molar excess Gibbs free energy described with the Margules function of the first order. Strong synergistic interactions exist between TB and SD particles (interaction coefficient with a magnitude of 10). Based on the temperature dependence of interaction coefficient and temperature dependence of TB and SD micellar molar fractions product logarithm, it follows that the molar excess entropy is zero. Therefore, although the surfactants TB and SD are structurally very different, their binary mixed micelles can still be described with regular solution theory (random mixing of TB and SD). However, the 2D ROESY spectrum indicates that the binary micellar pseudophase is not random in terms of the spatial distribution of TB and SD particles. Namely, intermolecular interactions between deoxycholic acid anions are missing in the binary mixed micelle. This results in the appearance of excess configuration entropy. However, a zero value of the total molar excess entropy and the existence of the first order Margules function for the molar excess Gibbs free energy means that the molar excess configurational entropy is compensated with the molar excess conformational entropy and that there are correlation effects between the excess configurational enthalpy and entropy as well as between the excess conformational enthalpy and entropy.

Interaction between Triton X100 and Brij 58 in their binary mixed micelles: Micellization in aqueous solution and aqueous solution of Poloxamer 188 at the range of temperature T = (273.15–323.15) K

The micellization of the binary mixture of surfactants Triton X100 – Brij 58 in an aqueous solution (with and without Poloxamer 188) was investigated using a spectrofluorimetric method with pyrene as a probe molecule. There are synergistic interactions between the micellar building units in the binary mixed micelles Triton X100 – Brij 58, which increase with increasing temperature. The analyzed binary mixed micelles possess molar excess entropy. The molar excess Gibbs free energy is a first-order Margules function from the surfactant (Triton X100 or Brij 58) molar fraction in the binary mixed micelles Triton X100 – Brij 58. Poloxamer 188, in the temperature range T = (273.15–323.15) K, does not form micelles. Poloxamer 188 in an aqueous surfactant solution (0.01 w/w) reduces the thermodynamic stabilization of the binary mixed micelle Triton X100 – Brij 58 concerning the state of the same binary mixed micelle when this polymer is not present in an aqueous solution. In the presence of Poloxamer 188, the thermodynamic destabilization of the binary mixed micelle Triton X100 – Brij 58 increases with increasing temperature.

Physicochemical characterization and activity coefficients at infinite dilution of molecular compound in poly(ethylene glycol)dimethyl ether and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate

This work is focused on determining the effectiveness of using hitherto unexplored extractants in separation processes. It is proposed to use poly(ethylene glycol) and the eutectic mixture composed of poly(ethylene glycol) with cyclic carbonate as separating agents in desulphurization of model fuel (heptane/thiophene) and alkanes from aromatic hydrocarbons (heptane/toluene) processes. The selected glycol was poly(ethylene glycol)dimethyl ether with an average molecular weight of M = 250 g·mol−1 (abbreviated as PEG250DME). The second component of the mixture was ethylene cyclic carbonate (abbreviated as EC). These components create a non-crystallizing mixture at a temperature below T = 203 K in the range of 25–40% ethylene carbonate, thus a mixture with the following composition 30% of EC and 70% of PEG250DME (wEC = 0.331) was investigated. For this purpose, the extensive research on the infinite dilution activity coefficients for 45 molecular compounds including alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, ethers, pyridine, thiophene, acetone, acetonitrile, and 1-nitropropane in both PEG250DME and {[PEG250DME] + [EC], wEC = 0.331} were determined. The experiment was performed at a temperature range from T = (308.15 to 338.15) K with an increment of 10 K using gas–liquid chromatography (GLC). Based on the experimental data, the infinite dilution capacity and selectivity of the PEG250DME and DES: {[PEG250DME] + [EC], wEC = 0.331} are presented to evaluate the effectiveness of using them as an extractant in the separation of aliphatic from aromatic hydrocarbons and sulfur compounds from alkanes. Obtained selectivity and capacity values for different separation processes are compared with the literature data for other separating agents presented in the available literature reports. From the temperature - dependence of the infinite dilution activity coefficient, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpy ΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated and discussed. Additionally, the liquid density and dynamic viscosity of pure PEG250DME and it’s eutectic mixture with EC as a function of temperature were determined. Both of the physicochemical parameters are important from a technological point of view.

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.

Deep eutectic solvent as a possible entrainer for industrial separation problems: Pre-screening tool for solvent selection

Deep eutectic solvents, as a new type of nature-welcoming solvents, have shown a great interest in different areas of science and in solvent extraction for industrial separation processes. In this present study, the infinite dilution activity coefficients γ13∞, have been measured for 31 volatile organic solvents (alkanes, alkenes, alkynes, aromatics, cycloalkanes, cycloalkenes, alcohols, ketones, and thiophene) in the deep eutectic solvent (1-ethyl-1-methylpyrrolidinium bromide + glycerol) prepared at (1:2 molar ratio) measured at temperature ranging from T = (313.15 to 343.15) K and at atmospheric pressure using gas liquid chromatography coupled with thermal conductivity detector (GC-TCD). The values of the partial molar excess enthalpies (ΔH1E,∞), entropies (TrefΔS1E,∞), and Gibbs free energy (ΔG1E,∞) at infinite dilution were calculated from the experimental data of γ13∞ attained over the temperature range mentioned above. Selectivities and capacities for two separation problems (cyclohexane/benzene and acetone/ethanol) were calculated fromγ13∞ and compared to the other investigated DESs, ILs as well as the currently used traditional solvents found from the literature. Furthermore, the selectivity and capacity results proved that the examined DES cannot be utilized in separation of (acetone/ethanol) but can be utilized for cyclohexane/benzene separation.

The investigation of the infinite dilution activity coefficients for molecular compounds in 1-(3-hydroxypropyl)-3-methyl-imidazolium thiocyanate

Measurements of infinite dilution activity coefficients of 46 organic solutes including alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, ethers, ketones, pyridine, thiophene, acetonitrile, and 1-nitropropane in ionic liquids (IL), 1-(3-hydroxypropyl)-3-methyl-imidazolium thiocyanate (abbreviated as [C1C3OHIM][SCN]) are reported in the temperature range from T = (318.15 to 358.15) K. Based on the experimental data, the infinite dilution capacity and selectivity of the studied IL are presented to evaluate the effectiveness of using it as an extractant in the separation of aliphatic from aromatic hydrocarbons and sulfur compounds from alkanes. Obtained selectivity and capacity values for different separation processes are compared with the literature data for other ionic liquids. From the temperature – dependence of the infinite dilution activity coefficient, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpyΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated and discussed.

The experimental physicochemical properties, 1H NMR, and COSMO-RS model calculations for the binary system containing water and 1-ethylimidazole

In order to explore the properties and molecular interactions in the binary systems of 1-alkylimidazole with molecular solvents, the system of x 1-ethylimidazole (herein referred to as 1-Eim) + (1-x) water, in the temperature range (288.15–328.15) K, the density ρ, sound velocity u, viscosity η, refractive index nD, pH and conductivity κ, and the 1H NMR δH, were measured at atmospheric pressure; the excess molar enthalpy HmE, the excess molar Gibbs free energy GmE, and the excess molar entropy SmE were predicted from the COSMO-RS model.The experimental and predicted properties indicate that the H-bonded interactions are the predominant interactions over the whole composition range. 1-Eim protons share more electron densities than water protons via the H-bonds, which are stronger between dissimilar molecules than between similar ones. The stable H-bonded structure of water molecules breaks when x is about 0.1, while the stable H-bonded structure of 1-Eim molecules forms when x is about 0.9. Temperature affects the H-bonded interactions more in the case of dissimilar molecules than similar molecules, especially in the water-rich region. The real mixing process is an enthalpy-driving spontaneous process with the liquid structure more ordered. A lower temperature more greatly benefits spontaneous mixing.

Development of Abraham model correlations for short-chain glycol-grafted imidazolium and pyridinium ionic liquids from inverse gas-chromatographic measurements

Infinite dilution activity coefficients and gas-to-liquid partition coefficients are herein reported for more than 45 organic solutes of varying polarity and hydrogen-bonding character dissolved within the ether-grafted ionic liquids 1-ethyl-3-(2-methoxyethyl)imidazolium bis(trifluoromethylsulfonyl)imide and N-(2-methoxyethyl)pyridinium bis(trifluoromethylsulfonyl)imide. Experimental values were determined in 10 K intervals from 323.15 to 373.15 K using the method of inverse gas chromatography. Measured infinite dilution activity coefficients were then used to determine the partial molar excess Gibbs free energies, enthalpies, and entropies associated with the dissolution of these model solutes into these two short-chain glycol-grafted ionic liquids. Finally, based on the measured infinite dilution activity coefficient data, Abraham model correlations have been established for solute transfer into these ionic liquids, including the calculation of cation-specific equation coefficients. The derived Abraham model correlations were found to back-calculate the observed partition coefficients to within 0.09 to 0.13 log units.

Thermodynamic Properties of Li-Sb Liquid Solution by QAM

The optimization of the thermodynamic properties of a liquid Li-Sb system is performed based on all available literature data. The description of the excess Gibbs energy as a function of temperature and composition is presented using a qualitative associate model (QAM), described in our earlier work on the Li-Pb system. The modeled molar mixing enthalpy changes, excess Gibbs energy and the molar excess entropy values are characterized by strong negative deviations from the ideal solution in the entire concentration range. It was found that the best correlation between experimental data and those calculated using QAM is observed if the Li3Sb and LiSb associates are assumed to be in the liquid Li-Sb solution. Calculations of the microscopic function, i.e., the concentration-concentration in the long-wavelength limit, (Scc(0)) excess stability function (ES) and short-range-order parameter (SRO(α)) show the extreme (maximum or minimum) values almost exactly for the concentrations of Li3Sb associate (and intermetallic phase in solid alloys) and LiSb. The quotient of real Scc(0) to this for the ideal solution (Scc(0)id) is characterized by a similar property to the mentioned structure factors.

Application of dicyanamide-based ionic liquid in separation of binary mixtures based on gamma infinity data measurements

In this research, the activity coefficients (γ13∞) at infinite dilution of 61 solutes were experimentally determined in the 1-(4-methoxy-4-oxobutyl)-3-methylimidazolium dicyanamide, [(C3COOMe)MIM][DCA]. The data were obtained using the gas-liquid chromatography technique (GLC). The experiment was carried out at a wide temperature range of (318.15 to 368.15) K, in 10 K intervals. The studied solutes included polar and non-polar compounds, as alkanes, alkenes, and alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters. Density, ρ, measurements for a range of temperatures (298.15–368.15) K, in 10 K intervals, for the chosen ionic liquid (IL) were undertaken at pressure, p = 101 kPa. Values of the gas-liquid partition coefficients, KL at infinite dilution, as well as the basic thermodynamic functions, such as partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements. The values of selectivity and capacity for the three chosen separation problems as heptane/thiophene, heptane/pyridine and heptane/1-nitropropane were calculated from γ13∞ values and compared to literature data for dicyanamide-based, ILs. The results from the study indicate that [(C3COOMe)MIM][DCA] has attractive capacity for all of the studied separation cases. These measurements allow to verify the possibility of use of investigated ionic liquid as an entrainer in liquid-liquid extraction.

The influence of the ionic liquids functionalization on interaction in binary systems with organic solutes and water – Thermodynamic data of activity coefficients at infinite dilution

In this work, the effect of IL’s functionalization of the interaction of IL with organic solutes and water at infinite dilution has been investigated. Based on the experimental activity coefficients at infinite dilution, (γ13∞) the possibility of using ionic liquids (ILs) in different separation processes, such as aliphatic from aromatic hydrocarbon (heptane/benzene, or cyclohexane/benzene), desulfurization and denitrification of model fuel (heptane/thiophene and heptane/pyridine) were investigated based on the experimental study of the activity coefficients at infinite dilution. The (γ13∞) values were determined for more than fifty different solutes including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, ethers, ketones, thiophene, acetonitrile, pyridine, 1-nitropropane and water in two ionic liquids: 4-(3-cyanopropyl)-4-methylmorpholinium tricyanomethanide, [Mo1,3CN][TCM] and 4-(3-hydroxypropyl)-4-methylmorpholinium tricyanomethanide, [Mo1,3OH][TCM]. The experiment was performed using inverse gas–liquid chromatography at a wide temperature range from T = (308.15 to 358.15) K. From the experimental data, the partial molar excess Gibbs energy (ΔG1E,∞), enthalpy (ΔH1E,∞) and entropy (Tref ΔS1E,∞) at infinite dilution were determined. The gas–liquid partition coefficients of the solutes, KL were also calculated. Finally, two the values of two factors important from separation point of view: selectivity (S12∞) and capacity (k2) at infinite dilution for few separation problems as hexane/benzene, cyclohexane/benzene, heptane/thiophene, and heptane/pyridine were calculated from γ13∞ and compared to literature values for other ionic liquids taken from available literature. Moreover, physicochemical properties of pure IL including liquid density and dynamic viscosity data, important from the technological point of view was determined at a wide temperature range.

Characterization of the solubilizing ability of short-chained glycol-grafted ammonium and phosphonium ionic liquids

Abstract Infinite dilution activity coefficients and gas-to-liquid partition coefficients are reported for >40 organic solvents dissolved in (2-methoxyethyl) triethylphosphonium bis(trifluoromethylsulfonyl)imide, (2-methoxyethyl)tributylphosphonium bis(trifluoromethylsulfonyl)imide, and (2-methoxyethyl)triethylammonium bis(trifluoromethylsulfonyl)imide in the temperature range from 323.15 K to 373.15 K. Experimental values were determined using the method of inverse gas chromatography. Measured infinite dilution activity coefficients are used to calculate the partial molar excess Gibbs free energy, enthalpy and entropy associated with dissolution of the organic solutes into the three ionic liquid solvents. Abraham model correlations for solute transfer into each ionic liquid solvent have also been determined from the measured infinite dilution activity coefficient data.

DCA]-based ionic liquids for the extraction of sulfur and nitrogen compounds from fuels: Activity coefficients at infinite dilution

Some petroleum processes need the removal of low level aromatic-sulfur and nitrogen compounds for many products, which are extremely important according to the new strict environmental regulations to reduce sulfur and nitrogen content compounds in liquid fuels. Thus the new, alternative solvents such as ionic liquids (ILs) have been proposed. ILs reveal a high selectivity and capacity of extraction of sulfur- and nitrogen-compounds from alkanes with little solvent loss during the process. The measurements of activity coefficients γ13∞ at infinite dilution of different solutes in the IL shows the effect of interactions between organic solutes, or water on the interfacial and bulk properties of the IL. The new (3-cyanopropyl)pyridinium dicyanamide, [N–C3CNPy][DCA] and (3-cyanopropyl)methylpyrrolidinium dicyanamide, [N–C3CNMPyr][DCA] were investigated in this work. The data were obtained using the gas-liquid chromatography technique. Measurements were undertaken at six temperatures, in 10 K intervals, in the range of (318.15–368.15) K. The solutes studied included both non-polar and polar compounds, as alkanes, alkenes, alkynes, as well as aromatic hydrocarbons, alcohols, water, ethers, ketones, and esters. The most important solutes used were thiophene, pyridine, and 1-nitropropane. Densities, ρ, measurements for a range of temperatures, T (298.15–368.15) K for the chosen ILs were undertaken at pressure, p = 101 kPa. The gas-liquid partition coefficients, KL at infinite dilution were calculated. The fundamental thermodynamic functions such as partial molar excess Gibbs energy, enthalpy and entropy at infinite dilution were calculated from the experimental data measurements to discuss the interaction between solutes and the ILs. The values of selectivity and capacity for three separation cases, viz. heptane/thiophene, heptane/pyridine, and heptane/1-nitropropane were calculated from γ13∞ values and compared to literature data for dicyanamide-based ILs. The Abraham solvation parameter model was presented for all solutes. The obtained results indicated that [N–C3CNPy][DCA] has large selectivity and capacity values for all three of the separation cases studied.

Activity coefficients at infinite dilution of organic solutes, using novel N-(2′, 3′-epoxypropyl)-N-methyl-2-oxopyrrolidinium chloride ionic liquid by GLC

The activity coefficients at infinite dilution (γ13∞) for 31 solutes, from the following classes of compounds: alkanes, cycloalkanes, alkenes, cycloalkenes, aromatic hydrocarbons, alcohols, ketones, acetonitrile, thiophene and water were determined using an ionic liquid (IL) modified column utilizing gas liquid chromatography. In this work, N-(2′, 3′-epoxypropyl)-N-methyl-2-oxopyrrolidinium chloride IL was used to determine the activity coefficients of organic solutes in the range of temperatures from T = 323.15 K–343.15 K, using 10 K intervals, under atmospheric pressure. From these experimental γ13∞ data, the following thermodynamic properties at infinite dilution, including partial molar excess Gibbs free energies (ΔGiE,∞), enthalpies ΔHiE,∞and entropy TrefΔSiE,∞ were computed. Furthermore, selectivity (Sij∞) and capacity (Kj∞) were also calculated from experimental value of γ13∞ for separation of mixtures such as (heptane/benzene, heptane/thiophene, hexane/benzene, water/butanol and hexane/ethanol) at T = 323.15 K–343.15 K. Generally, the results of this work indicate that the investigated IL has good potential for separating aliphatic solutes from aromatic ones. Specifically, the chosen IL reduces the retention time of most of the solutes used, compared to other reported ILs. Furthermore, the findings of this study suggest that this IL [N(2′,3′-epoxypropyl)-N-methyl-2-oxopyrrolidinium chloride] may be useful for future applications such as separation and purification in petrochemical industries.