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A novel method based on unimolecular quantum mechanical calculation has been used to predict the binary vapor−liquid equilibria (VLE) of ionic liquids (ILs).The recently developed conductor-like screening model (COSMO), along with the most common quantum chemical package of GAUSSIAN 03, has been used in this work. These conductor-like screening model calculations combined with exact statistical thermodynamics provide the information necessary for the evaluation of molecular interactions in liquids. An effective parametrization has been done using 10 associated and 22 binary nonassociated systems; these 32 systems are all non-ILs. The effective contact surface area a eff and the hydrogen-bonding coefficient c hb have been estimated using a sequential scheme. The root-mean-square error obtained for excess Gibb's free energy is ∼0.1 for a eff and c hb. Values for α‘ (misfit constant), σhb (cutoff surface charge density for hydrogen bonding), and cavity radii (r i ) as given in the literature have been used as default. COSMO-RS has then been used to predict the vapor−liquid equilibria for 116 non-IL binary sets out of which 33 are azeotropic systems. COSMO-RS predicts a better pressure a priori with a relative error of ∼4%, as compared to a 7−8% error for the Wilson/NRTL/UNIQUAC models. Being an a priori model, it does fall short with respect to absolute average deviation in mole fraction for the vapor phase:  0.025 as compared to ∼0.0075 for the Wilson, NRTL, and UNIQUAC models. Having thus benchmarked extensively, the COSMO-RS model has then been used to predict the VLE for 13 systems based on five imidazolium ILs:  (a) 1-methyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [MMIM] [(CF3SO2)2N] with (1) benzene and (2) cyclohexane; (b) 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [EMIM][(CF3SO2)2N] with (3) acetone, (4) 2-propanol, and (5) water; (c) 1-butyl-3-methyl-imidazolium bis(trifluoromethanesulfonyl) imide [BMIM][(CF3SO2)2N] with (6) acetone, (7) 2-propanol, and (8) water; (d)1-methyl-3-methylimidazolium dimethylphosphate [MMIM][(CH3)2PO4] with (9) acetone, (10) tetrahydrofuran, and (11) water; and (e) 1-ethyl-3-methylimidazolium ethoxysulfate [EMIM][C2H5OSO3] with (12) benzene and (13) cyclohexane. The root-mean-square deviation for pressure prediction is 6% as compared to 4%, 1.45%, and 3.13% for the Wilson, NRTL, and UNIQUAC models, respectively. The mole fraction in the vapor phase has also been predicted, confirming the negligible presence of ionic liquids in the vapor phase even at very low pressures.

Five-and six-membered heteroaromatic nitrogen compounds play an inhibiting role in the hydrodesulfurization of diesel oil. In this work, the ionic liquids (ILs) are used as green solvents to remove such compounds by liquid-liquid extraction (LLE). Approximately 168 ILs comprising cations which include 1-ethyl-3methylimidaozlium [EMIM], 1-ethylpyridinium [EPY], 1-ethyl-1-methyl pyrrolidinium [EPYRO], 1-ethyl-1-methylpiperidinium [EMPIP], 4-ethyl-4-methyl morpholinium [EMMOR], and 1,2,4-trimethylpyrazolium[TMPYZO] combined with 26 anions were investigated in this work. The infinite dilution activity coefficient (IDAC) was predicted through the conductor-like screening model for real solvents (COSMO-RS) model in order to screen the potential solvents. Initially the model was benchmarked via IDAC and LLE predictions. LLE was predicted for four reported ternary systems in which a nitrogen heterocycle was one of the compounds. The average root-mean-square deviation (rmsd) obtained was 10%. The IDAC values were predicted for pyridine in two ionic liquids, namely [BMIM][BF 4 ] and [EMIM][TOS], with a root-mean-square (rms) error of 8%. Thereafter the selectivity, capacity, and performance index at infinite dilution were calculated to evaluate the performance. It was found that the five-membered nitrogen species having high delocalized electron density possessed 3 orders of magnitude higher selectivity than the six-membered nitrogen species. For the fivemembered ring structures, the selectivity was found to follow the orderFor the six-membered heterocycle, it followed the order [EPY] >Irrespective of nitrogen heterocycle, anions such as thiocyanate [SCN] and acetate [Ac] gave high values of selectivity. In general cations without aromatic rings such as [EPYRO], [EMPIP], and [EMMOR] gave higher selectivity and capacity irrespective of the nitrogen heterocycle.

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Separation of aliphatic and aromatic compounds was studied using the high molecular weight trihexyl-tetradecylphosphonium cation (thtd-Ph) based ionic liquids (ILs) with the anions chloride [Cl], tetrafluoroborate [BF 4 ], and bis(trifluoromethane sulfonylimide)[(Tf) 2 N]. Infinite dilution activity coefficients (γ ∞ ) for these novel solvents have been measured at T ) (308.15, 318.15, and 328.15) K, using gas-liquid chromatography. The aliphatic solutes studied were normal alkanes (pentane, hexane, heptane, octane), alkenes (hexene, heptene, octene), alkynes (hexyne, heptyne, octyne), cycloalkanes (cyclopentane, cylcohexane, cycloheptane), and alcohols (methanol, ethanol). The aromatic solute studied was benzene. The molar excess enthalpy at infinite dilution (H E,∞ ) was calculated using the temperature dependency of γ ∞ data. The selectivity values for the phosphonium-based ILs indicate a poorer separation capability than imidazolium-or pyridinium-based ILs. The values of γ ∞ have been found to be in the following order: alkanes > alkenes > alkynes > aromatics. Selectivity values indicate the IL [thtd-Ph][BF 4 ] as an effective solvent for the separation of benzene + alcohol systems. The γ ∞ measurements on the phosphonium ILs were further validated using the a priori COSMO-RS method. The COSMO-RS prediction was first benchmarked on the values obtained with [thtd-Ph] tris(pentafluoroethyl) trifluorophosphate, which gave the average absolute deviation (AAD) to be 15 %. Using COSMO-RS, γ ∞ values were obtained for the three phosphonium ILs, and the corresponding AADs were 9 %, 8 %, and 16 %.

in Wiley InterScience (www.interscience.wiley.com).Ionic liquids with their limitless combination of cations and anions can offer an optimal solvent for a specific purpose. But not all corresponding experimental studies are possible as they will be time consuming and expensive. A judicious screening of the various possible solvents is required to select the proper ionic liquid. Conductor-like screening model (COSMO) along with its extension to real solvents can be used for these predictions. In this work, modified version COSMO_LL has been used to predict the liquidliquid equilibria (LLE) for 32 ternary systems, available in literature, each having an ionic liquid. A complete dissociation of cations and anions of the ionic liquid has been assumed. The root mean square deviation for all these systems is ;9% which is excellent when compared with ;50% obtained for predictions using the nondissociated composite molecule. Additionally, experimental LLE data has been collected for four ternary systems, namely: (a)

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A novel method based on unimolecular quantum mechanical calculations has been used to predict the multicomponent liquid-liquid equilibria (LLE). The recently developed COnductor-like Screening MOdel (COSMO), along with the most common quantum chemical package of Gaussian03 has been used in this work. COSMO-RS combines the COSMO model calculations with exact statistical thermodynamics of pairwise interacting surface segments and has been used for the evaluation of molecular interactions in liquids. COSMO-RS has been used to predict the LLE for 158 multicomponent data sets, which consist of 80 ternary, 9 quaternary, and 4 quinary systems, several of which are examined at different temperatures. The effective contact surface area (a eff ), the hydrogen-bonding coefficient (c hb ), and the cutoff surface charge density for hydrogen bonding (σ hb ) have been estimated simultaneously, using 10 ternary data sets that consist of 11 different functional groups (CH 3 , CH 2 , CH, CHdCH 2 , C-CH 3 , OH, CH 2 O, C-(CH 2 ), COO, C-Cl, CH 2 -CN) and 9 different solvents (sulfolane, dimethyl sulfoxide, N-methyl pyrrolidone, furfural, propylene carbonate, triethylene glycol, tetraethylene glycol, ethylene carbonate, dicyanobutane). Cavity radii (r i ) values up to 1.17 times greater than the Bondi radius have been used. The prediction has been initially benchmarked on the octane-toluene-sulfolane system at three temperatures: 25, 35, 45 °C, for which the root-mean-square deviations (RMSDs) are <1% for mole fraction predictions. Thereafter, the LLE has been predicted for 158 multicomponent data sets. An important aspect of our work is that, for the first time, quaternary and quinary systems have been predicted using COSMO-RS. The overall RMSD is <5% for multicomponent systems, compared to ∼1% for NRTL and UNIQUAC models and 5% for UNIFAC models.