Infinite Dilution Of Organic Solutes Research Articles

Deep eutectic solvents as sustainable solvents for industrial separation problems: A recent update

Deep eutectic solvents (DESs) are ionic liquid analogues that consist of Lewis or Brønsted acids and bases. These systems are characterized by a substantial decrease in melting points as compared to those of the neat constituents. Activity coefficients at infinite dilution of organic solutes is used as a screening tool for extracting solvents, an approach that is useful for identifying acceptable precursors and assessing separation performance in practical applications. This review assesses the effectiveness of DESs as solvents for chemical separations wherein the data is presented for the activity coefficients at infinite dilution for 33 solutes in different DESs at various temperatures. Additionally, the selectivities and capacities for various solute extraction problems are also appraised from the activity coefficients at infinite dilution at T = 323.15 K; capacity represents the solvent's ability to extract the component.

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 and Activity Coefficients at Infinite Dilution for Organic Solutes in Trialkyl-Substituted Imidazolium-Based Ionic Liquid 1-Propyl-2,3-dimethylimidazolium Thiocyanate

Thermodynamics and Activity Coefficients at Infinite Dilution for Organic Solutes in Trialkyl-Substituted Imidazolium-Based Ionic Liquid 1-Propyl-2,3-dimethylimidazolium Thiocyanate

Imidazolium Chloride Ionic Liquid Mixtures as Separating Agents: Fuel Processing and Azeotrope Breaking.

Relevant chemical separations for the petrochemical and chemical industries include the removal of aromatic hydrocarbons from aliphatics, the desulfurization and denitrification of fuels, and the separation of azeotropic mixtures containing alkanols. In an attempt to contribute to the development of novel technologies, the potentialities of imidazolium chloride ionic liquid (IL) mixtures as separation agents were investigated. Selectivities, capacities, and solvent performance indices were calculated through the activity coefficients at infinite dilution of organic solutes and water in the imidazolium chloride IL: [C8mim]Cl, [C12mim]Cl, and the equimolar mixture of [C4mim]Cl and [C12mim]Cl. Results show that the imidazolium chloride IL might be appropriately tailored for specific purposes, in which an increase in the proportion of cations containing larger alkyl chains tends to increase the overall affinity with organic solutes. The IL designer solvent concept was explored by comparing the IL equimolar mixture results with the intermediary [C8mim]Cl. The COSMO-RS thermodynamic model was also applied, showing it to be a promising tool for a fast qualitative screening of potential separation agents for specific separation processes.

Measurements of Activity Coefficients at Infinite Dilution for Organic Solutes in the Ionic Liquids N-Ethyl- and N-Octyl-N-methylmorpholinium Bis(trifluoromethanesulfonyl)imide. A Useful Tool for Solvent Selection.

In recent years, many papers describing ionic liquids (IL) as promising solvents in separation techniques have been published. The conscious choice of appropriate ionic liquid as absorption media in effective extraction of selected types of analytes requires deeper understanding of the analyte−IL interactions. Therefore, intensive research is conducted to determine the values of activity coefficient at infinite dilution, which allows us to characterize the nature of these interactions. Based on the inverse gas chromatography retention data, activity coefficients at infinite dilution of 48 different organic compounds in the ionic liquids N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C2C1Mor][TFSI] and N-octyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C8C1Mor][TFSI] were determined. The measurements covered a broad range of volatile organic compounds, including n-alkanes, n-alkenes, n-alkynes, alcohols, aldehydes, ketones, aromatic compounds and common polar solvents, representing different types of interactions. Activity coefficients at infinite dilution were measured in the temperature range from 313.15 to 363.15 K. The excess partial molar enthalpies and entropies at infinite dilution were determined. Selectivity at infinite dilution was also calculated for exemplary separation processes in the hexane/benzene system. The obtained results were analyzed and compared with literature data for ionic liquids containing the same anion [TFSI]¯ and different cations. The study results indicate that some potential applications of the investigated ionic liquids in separation problems exist.

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.

Characterization of bis(fluorosulfonyl)imide based ionic liquids by gas chromatography

Infinite dilution thermodynamic properties of organic solutes dissolved in four bis(sulfonyl)imide ionic liquids namely 1-butyl-1-methylpyrrolidinium bis(fluorosulfonyl)imide, N-propyl-N-methylpyrrolidinium bis(fluorosulfonyl)imide, 1-ethyl-1-methylimidazolium bis(fluorosulfonyl)imide and 1-methyl-1-propylpiperidinium bis(fluorosulfonyl)imide were measured in a large range of temperature using inverse gas chromatography. The characterization of ILs using the Abraham solvation model indicates that the cation has an impact on the polarizability and on the acidity of the solvent. The derived Abraham model correlations rigorously describe the experimental partition coefficient data to within 0.09 (or fewer) log units. In addition, the activity coefficient at infinite dilution of organic solutes in these ILs was predicted using the conductor-like screening model for real solvents (COSMO-RS). It was found that COSMO-RS give a reasonable representation of experimental data. Then, selectivity and capacity at infinity dilution have been determined for the separation problems (thiophene/water), (benzene/water), (acetone/water), (1-butanol/water), (acetonitrile/water) and (pyridine/water) at 323.15 K.

Measurements of activity coefficients at infinite dilution for organic solutes in two quaternary ammonium-based ionic liquids [DDA][ClO4] and [DDA][BF4

The paper presents new data on the activity coefficient at infinite dilution (γ13∞) for 29 various organic solutes: alkanes, alkenes, al-kynes, cycloalkanes, alcohols, ethers, ketones and aromatic hydrocarbons in two quaternary-ammonium based ionic liquids (quat-based ILs): didecyldimethylammonium perchlorate [DDA][ClO4] and didecyldimethylammonium tetrafluoroborate [DDA][BF4]. The activity coefficient at infinite dilution and physicochemical properties of two mentioned ionic liquids, were determined by inverse gas chromatography at four different temperatures: 308K, 323K, 338K and 353K. Additionally, on the basis of the specific retention volume (Vg0) the Flory – Huggins interaction parameters (χ∞) were determined. In order to identify the fundamental interaction between solute and solvent inside the column, the partial molar excess enthalpies at infinite dilution (ΔH1E,∞) were calculated on the basis of experimental γ13∞ values. The selectivity (Sij∞) and capacity (kj∞) at infinite dilution for a few different separation problems: hexane/benzene, cyclohexane/benzene and hexane/tetrahydrofuran were calculated from the experimental γ13∞ values to evaluate the possible use of the ionic liquids studied as a new class of solvents in liquid-liquid extraction and in other extraction or microextraction methods. The values of the above-mentioned parameters were compared and discussed taking into regard the chemical structures of both quaternary ammonium-based ionic liquids, including the same cation and their interactions with the organic solute.

Thermodynamics and activity coefficients at infinite dilution for organic solutes in the ionic liquid 1-butyl-1-methylpyrrolidinium dicyanamide

The activity coefficients at infinite dilution, γ13∞, for 46 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane in the ionic liquid (IL) 1-butyl-1-methylpyrrolidynium dicyanamide, [BMPYR][DCA] were determined by gas-liquid chromatography at five temperatures in range of (313.15–373.15) K at pressure, p = 101 kPa. The thermodynamic functions at infinite dilution as partial molar excess Gibbs free energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy term TrefΔS1E,∞ and the gas-liquid partition coefficients, KL at infinite dilution were calculated from the experimental γ13∞ values obtained over the temperature range. The values of selectivity and capacity for few separation problems as n-heptane/benzene, n-heptane/thiophene, n-heptane/1-heptyne, and ethylbenzene/styrene at T = 323.15 K were calculated from γ13∞ and compared to literature values for [DCA]-based ionic liquids and [BMPYR]-based ILs. In comparison with the former measured [BMPYR][TCM], or [BMPYR][SCN] ILs, the [DCA]-based IL presents high selectivities for the separation of aromatic hydrocarbons from aliphatic hydrocarbons, and especially for the extraction of thiophene, or pyridine from n-heptane with slightly lower capacity than those for [BMPYR][TCM], or [BMPYR][SCN]. New data shows that [BMPYR][DCA] IL may be proposed as an alternative solvent for the separation of aliphatic from aromatic hydrocarbons.

Determination of Activity Coefficients at Infinite Dilution of Organic Solutes in the Ionic Liquid 1-(2-Hydroxyethyl)-3-methylimidazolium Nonafluoro-1-butanesulfonate Using Gas–Liquid Chromatography

Activity coefficients at infinite dilution (γi∞) for a variety of organic solutes (alkanes, cycloalkanes, alkenes, alkyl benzenes, alcohols, 1,4-dioxane, acetone, acetonitrile, tetrahydrofuran, chloroform, and dichloromethane) in the ionic liquid (IL) 1-(2-hydroxyethyl)-3-methylimidazolium nonafluoro-1-butanesulfonate ([C2OHmim][C4F9SO3]) have been determined by gas–liquid chromatography using the IL as the stationary phase. The measurements were conducted in the temperature range from 303 to 353 K. The partial molar excess Gibbs energies (ΔGiE,∞), enthalpies (ΔHiE,∞), and entropies (ΔSiE,∞) at infinite dilution of the solutes in the ionic liquid were calculated from the temperature dependence of the values of γi∞. Values of selectivity sij∞ and capacity kj∞ at T = 323.15 K for the IL [C2OHmim][C4F9SO3] were calculated for both cyclohexane/benzene and benzene/methanol binary systems. The results obtained from this work were compared with reported literature data for other [C2OHmim] based ILs.

Measurements of activity coefficient at infinite dilution for organic solutes in tetramethylammonium chloride + ethylene glycol deep eutectic solvent using gas-liquid chromatography

Deep eutectic solvents (DESs) are considered as the new ionic liquids (ILs) analogues that have emerged as potential alternative ‘green’ solvents, for a diversity of applications. In this study, a type III DES based on ammonium salt was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Activity coefficients at infinite dilution, γ13∞ for 19 organic solutes in the tetramethylammonium chloride + ethylene glycol DES were measured by the gas-liquid chromatography (GLC) method at four temperatures in the range from (313.15–343.15) K. Experimental measurements were undertaken with an overall uncertainty of ±5.4%. The effect of the structure of the solutes on γ13∞ was also investigated. For all investigated solutes, Gibbs helmholtz relationship was utilised to derive partial molar excess enthalpy values at infinite dilution (ΔHiE,(∞)) from experimental limiting activity coefficient data. From selectivity (Sij∞) and capacity (kj∞) values at infinte dilution, it was concluded that the investigated DES has the potential to replace a number of industrial solvents for the separation of various industrial mixtures.

Activity coefficients at infinite dilution for organic solutes dissolved in two 1,2,3-tris(diethylamino)cyclopenylium based room temperature ionic liquids

Infinite dilution activity coefficients and gas-to-liquid partition coefficients have been determined for at least 45 different organic solutes of varying polarity and hydrogen-bonding character dissolved in anhydrous 1,2,3-tris(diethylamino)cyclopropenylium dicyanamide, ([TDC]+[DCA]−), and 1,2,3-tris(diethylamino)cyclopropenylium bis(trifluoromethylsulfonyl)imide, ([TDC]+[Tf2N]−). The measured infinite dilution activity coefficients were used to calculation selectivity values for various practical separation problems. Computations showed ([TDC]+[DCA]−) should afford better performance in hexane/benzene and hexane/pyridine separation problems than sulfolane and N-methyl-2-pyrrolidone. Abraham model correlations were derived for predicting solute transfer into both ([TDC]+[DCA]−) and ([TDC]+[Tf2N]−) from water and from the gas phase. The derived correlations describe the observed solute transfer partition coefficients to within 0.13 (or fewer) log units.

Thermodynamics and activity coefficients at infinite dilution for organic solutes in the ionic liquid 1-hexyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide

Activity coefficients at infinite dilution (γi∞) and gas-liquid partition coefficients (KL) for organic solutes: n-alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, and chloromethanes in the ionic liquid (IL) 1-hexyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([HMMIM][NTf2]) have been measured by the gas-liquid chromatographic method (GLC) in the temperature range of (313.15–353.15)K. The thermodynamic functions at infinite dilution as partial molar excess enthalpies at infinite dilution (H‾iE,∞) were derived from the temperature dependence of the γi∞ values. Gibbs energies (G‾iE,∞) and entropies (TrefS‾iE,∞) of organic solutes in [HMMIM][NTf2] at a reference temperature Tref=298.15K were also calculated from the γi∞ values. The solubility parameters of the IL [HMMIM][NTf2] were determined by two methods. Selectivity (Sij∞) and capacity (kj∞) at infinite dilution at 323.15K have been determined for n-hexane (i)/benzene (j), cyclohexane (i)/benzene (j). The results were analyzed in comparison to literature data for alkylimidazolium-based ILs with [NTf2]−. For three isomeric xylenes separation problems, selectivity at 323.15K were also obtained from the γi∞ values.

Separation of aliphatic from aromatic hydrocarbons and sulphur compounds from fuel based on measurements of activity coefficients at infinite dilution for organic solutes and water in the ionic liquid N,N-diethyl-N-methyl-N-(2-methoxy-ethyl)ammonium bis(trifluoromethylsulfonyl)imide

The activity coefficients at infinite dilution, γ13∞, for 53 different solutes including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, ethers, ketones, thiophene, acetonitrile, pyridine, 1-nitropropane and water in the ionic liquid N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [COC2N1,2,2][NTf2] were determined using inverse gas-liquid chromatography. The experiment has been performed at five temperatures over the range of (318.15 to 358.15)K. From experimental results, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpy ΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated. Additionally, the gas-liquid partition coefficients of the solutes, KL were calculated. The value of selectivity, S12∞ and capacity, k2∞ at infinite dilution for hexane/benzene, cyclohexane/benzene, heptane/thiophene and heptane/pyridine separation processes were calculated directly from γ13∞. These parameters are compared to literature values of S12∞ and k2∞ for other ionic liquids and NMP, or sulfolane – solvents commercially used on an industrial scale in separation processes. Moreover, physicochemical properties of pure ILs that is: density, viscosity and surface tension have been determined as a function of temperature and basic thermal properties of pure [COC2N1,2,2][NTf2] were measured using DSC technique.

Measurements of activity coefficients at infinite dilution of organic solutes in the ionic liquid 1-ethyl-3-methylimidazolium ethylphosphonate [EMIM][(EtO)(H)PO2] using gas-liquid chromatography

Activity coefficients at infinite dilution γ12∞ and gas-liquid partition coefficients KL of selected hydrocarbons, alcohols, haloalkanes, nitrogen and sulfur containing compounds in the ionic liquid 1-ethyl-3-methylimidazolium ethylphosphonate [EMIM][(EtO)(H)PO2] were determined by inverse gas chromatography at five temperatures within the range (323.15 to 363.15) K. Retention data were used to calculate the selectivity and capacity for four separation problems hexane/benzene, hexane/thiophene, hexane/pyridine and cyclohexane/benzene. The selectivity values of 1-ethyl-3-methylimidazolium ethylphosphonate investigated in this study are greater than those obtained with sulfolane and N-methyl-2-pyrrolidone (NMP). These results indicate the potential use of the IL in extractive separation processes.

Activity Coefficients at Infinite Dilution of Organic Solutes and Water in Tributylethylphosphonium Diethylphosphate Using Gas–Liquid Chromatography: Thermodynamic Properties of Mixtures Containing Ionic Liquids

In this work, new set of experimental activity coefficients at infinite dilution, γ13∞ for 51 various organic solutes such as alkanes, 1-alkenes, 1-alkynes, cycloalkanes, aromatic hydrocarbons, alcohols, thiophene, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, and water in tributylethylphosphonium diethylphosphate, [P2,4,4,4][DEP] have been measured in temperature range T = (328.15 to 368.15) K by gas–liquid chromatography, GLC. From experimental data the partial molar excess Gibbs free energies ΔG1E,∞, enthalpies ΔH1E,∞, and entropies TrefΔS1E,∞ at infinite dilution were calculated. Additionally the gas–liquid partition coefficients, KL were determined. Moreover, capabilities of the studied ionic liquid in several liquid–liquid extraction processes are evaluated by selectivity and capacity at infinite dilution. These parameters were compared to the values from the recent literature for other ionic liquids with phosphonium cation or diethylphosphate anion. Additionally, basic thermophysical cha...

Activity coefficients at infinite dilution for organic solutes dissolved in two 1-alkylquinuclidinium bis(trifluoromethylsulfonyl)imides bearing alkyl side chains of six and eight carbons

Infinite dilution activity coefficients and gas-to-liquid partition coefficients are reported for 47 and 45 organic probe molecules dissolved in 1-hexylquinuclidinium bis(trifluoromethylsulfonyl)imide ([Quin6]+[Tf2N]−) and 1-octylquinuclidinium bis(trifluoromethylsulfonyl)imide ([Quin8]+[Tf2N]−), respectively, as determined by inverse gas chromatography in the temperature range of 313K to 353K. The measured partition coefficient data were converted to water-to-liquid partition coefficients using standard thermodynamic relationships and published gas-to-water partition coefficient data. Both sets of calculated partition coefficient data for each ionic liquid solvent were analyzed in terms of the Abraham general solvation model. Mathematical correlations derived from the Abraham model described the measured partition coefficient data to within 0.14 or fewer log units.

Measurements of activity coefficients at infinite dilution of organic solutes and water on polar imidazolium-based ionic liquids

The activity coefficients at infinite dilution, γ13∞, of 55 organic solutes and water in three ionic liquids with the common cation 1-butyl-3-methylimidazolium and the polar anions Cl−, [CH3SO3]− and [(CH3)2PO4]−, were determined by (gas+liquid) chromatography at four temperatures in the range (358.15 to 388.15)K for alcohols and water, and T=(398.15 to 428.15)K for the other organic solutes including alkanes, cycloalkanes, alkenes, cycloalkenes, alkynes, ketones, ethers, cyclic ethers, aromatic hydrocarbons, esters, butyraldehyde, acetonitrile, pyridine, 1-nitropropane and thiophene. From the experimental γ13∞ values, the partial molar excess Gibbs free energy, G‾mE,∞, enthalpy H‾mE,∞, and entropy S‾mE,∞, at infinite dilution, were estimated in order to provide more information about the interactions between the solutes and the ILs. Moreover, densities were measured and (gas+liquid) partition coefficients (KL) calculated. Selectivities at infinite dilution for some separation problems such as octane/benzene, cyclohexane/benzene and cyclohexane/thiophene were calculated using the measured γ13∞, and compared with literature values for N-methyl-2-pyrrolidinone (NMP), sulfolane, and other ionic liquids with a common cation or anion of the ILs here studied. From the obtained infinite dilution selectivities and capacities, it can be concluded that the ILs studied may replace conventional entrainers applied for the separation processes of aliphatic/aromatic hydrocarbons.

Activity coefficients at infinite dilution for organic solutes and water in 1-ethyl-1-methylpyrrolidinium lactate

Synthesis of new ionic liquid 1-ethyl-1-methylpyrrolidinium lactate (racemate), [EMPYR][Lac] was performed. The characterization of the new compound by NMR spectra, elementary analysis, water content, and TG/DTA is presented. The activity coefficients at infinite dilution, γ13∞, for 54 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, ethers, ketones, acetonitrile, pyridine, 1-nitropropane, thiophene, and esters in the [EMPYR][Lac] were determined by gas–liquid chromatography for most of the solutes at eight temperatures within the range of (308.15 to 378.15)K and for alcohols and water at higher temperatures in a range of (358.15 to 408.15)K. The partial molar excess Gibbs energy, ΔG1E,∞, enthalpy ΔH1E,∞, and entropy term TrefΔS1E,∞ at infinite dilution were calculated from the experimental γ13∞ values obtained over the temperature range. The values of selectivity for few separation problems as hexane/hex-1-ene, cyclohexane/cyclohexene and hexane/benzene were calculated from γ13∞ and compared to literature values for pyrrolidinium-based ionic liquids (ILs) on the same separation problems. In comparison with the former measured ILs, the [EMPYR][Lac] presents quite high selectivity for the separation of alkenes from aliphatic hydrocarbons, an average capacity for alkenes. The data presented here shows that [EMPYR][Lac] may be proposed as an alternative solvent for the separation of alkenes from the aliphatic hydrocarbons.

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.