Mixing and decomposition behavior of {[4bmpy][Tf2N] + [emim][EtSO4]} and {[4bmpy][Tf2N] + [emim][TFES]} ionic liquid mixtures

Mixing ionic liquids (ILs) has been revealed as a useful way to finely tune the properties of IL-based solvents. The scarce available studies on IL mixtures have shown a quasi-ideal behavior of their physical properties. In this work, we have performed a thermophysical characterization of two binary IL mixtures, namely {4-methyl-N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([4bmpy][Tf₂N]) + 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO₄])} and {[4bmpy][Tf₂N] + 1-ethyl-3-methylimidazolium 1,1,2,2-tetrafluoroethanesulfonate [emim][TFES]}. Both binary IL mixtures have been recently proposed as promising solvents in the (liquid + liquid) extraction of aromatic hydrocarbons from mixtures with alkanes. Densities, viscosities, refractive indices, thermal stability, and specific heats of the {[4bmpy][Tf₂N] + [emim][EtSO₄]} and {[4bmpy][Tf₂N] + [emim][TFES]} IL mixtures have been measured as a function of both temperature and composition. Dynamic viscosities, refractive indices, and thermal stability of the {[4bmpy][Tf₂N] + [emim][EtSO₄]} mixture have exhibited strong deviations from the ideality, in contrast with the quasi-ideal properties of the {[4bmpy][Tf₂N] + [emim][TFES]} mixture and the behavior of the imidazolium and pyridinium-based IL mixtures studied hitherto. The reliability of predictive methods of the thermophysical properties of the mixtures has also been evaluated.     

Coexistence curves of ionic liquid in oil microemulsions of {[bmim][BF4] + T-X100 + cyclohexane} with various molar ratio of [bmim][BF4] to T-X100 in the critical region

The coexistence curves (T, n), (T, Φ), and (T, Ψ) (n, Φ, and Ψ are the refractive index, volume fraction, and effective volume fraction, respectively) for the ionic liquid microemulsion systems of {polyoxyethylene tert-octylphenyl ether (T-X100) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) + cyclohexane} with various molar ratio (ω) of [bmim][BF₄] to T-X100 have been determined by measuring refractive indices at a constant pressure in the critical region. The critical temperatures (T_c) and critical volume fraction (Φ_c) were obtained for the ionic liquid microemulsions. The critical exponents were deduced precisely from the coexistence curves within about 1 K below T_c and the values were consistent with the 3D Ising value.     

Experimental investigation of incipient equilibrium conditions for the formation of semi-clathrate hydrates from quaternary mixtures of (CO2 + N2 + TBAB + H2O)

The three-phase (vapour + liquid + solid) equilibrium conditions for semi-clathrates formed from three mixtures of (CO₂ + N₂), in aqueous solutions of tetra-butyl ammonium bromide (TBAB), were measured in an isochoric reactor. The experiments were conducted at temperatures between (281 and 290) K, at pressures between (1.9 and 5.9) MPa and in aqueous TBAB solutions of w_TBAB = (0.05, 0.10, and 0.20). The experimental results obtained in this study were compared with previously obtained results for gas hydrates, formed from the same three mixtures of (CO₂ + N₂) and it was observed that semi-clathrates formed at a substantially lower pressure than did gas hydrates.     

(Solid + liquid) metastable equilibria in quaternary system (Li2SO4 + K2SO4 + Li2B4O7 + K2B4O7 + H2O) at T = 288 K

Metastable equilibrium solubilities and properties such as densities, conductivity, pH, refractive index, and viscosity of the solution were determined experimentally. According to the experimental data, the metastable equilibrium phase diagram was plotted. In the phase diagram, there are three invariant points, seven univariant curves, five fields of crystallization: Li₂SO₄ · H₂O, K₂SO₄, Li₂B₄O₇ · 3H₂O, K₂B₄O₇ · 4H₂O, and K₂SO₄ · Li₂SO₄. The double salt K₂SO₄ · Li₂SO₄ was found in the quaternary system metastable equilibria. Lithium sulfate (Li₂SO₄) has the highest concentration and strong salting-out effects on other salts.Also, the relationship diagram between the properties and the ion concentration of solution was constructed. It can be seen from the relationship diagram that the equilibrium solution density values, viscosity values, and refractive index values are increased apparently with the rise of sulfate ion concentration, reaching the maximum values at eutonic point F3. Electrical conductivity values and pH values, however, fall down with the rise of ion concentration on the whole.     

Phase equilibria for H2 + CO2 + H2O system containing gas hydrates

Isothermal phase equilibrium (pressure–composition in the gas phase) for the ternary system of H₂ + CO₂ + H₂O has been investigated in the presence of gas hydrate phase. Three-phase equilibrium pressure increases with the H₂ composition of gas phase. The Raman spectra suggest that H₂ is not enclathrated in the hydrate-cages and behaves only like the diluent gas toward the formation of CO₂ hydrate. This fact is also supported by the thermodynamic analysis using Soave–Redlich–Kwong equation of state.     

Phase behavior of ternary mixtures {aliphatic hydrocarbon + aromatic hydrocarbon + ionic liquid}: Experimental LLE data and their modeling by COSMO-RS

Separation of aromatic and aliphatic hydrocarbons is a complex process in the petrochemical industry due to overlapping boiling points and azeotrope formation. In this paper, liquid extraction of aromatic compounds (toluene and ethylbenzene) from aliphatic compounds (hexane and cyclohexene) using ionic liquids (1-butyl-3-methylimidazolium methylsulfate, BMimMSO₄, 1-propyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, PMimNTf₂, and 1-butyl-3-methylimidazolium bis{trifluoromethylsulfonyl}imide, BMimNTf₂) as solvent was studied. (Liquid + liquid) equilibrium (ELL) data for the ternary systems {hexane (1) + ethylbenzene (2) + BMimMSO₄, or BMimNTf₂, or PMimNTf₂ (3)}, {hexane (1) + toluene (2) + BMimMSO₄ (3)} and {cyclohexene (1) + ethylbenzene (2) + BMimMSO₄ (3)} were experimentally determined at T = 298.15 K and atmospheric pressure. Moreover, an analysis of the influence of the structure of each compound on the phase behavior was also carried out. The ability of the studied ILs to separate aromatic from aliphatic compounds was evaluated in terms of the solute distribution ratio, β, and the selectivity, S. The Non Random Two-Liquid (NRTL) and UNIversal QUAsiChemical (UNIQUAC) thermodynamic models were used to correlate the experimental LLE data. Furthermore, the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) was applied to predict the (liquid + liquid) equilibrium. The suitability of this model to describe the phase behavior of the studied mixtures was evaluated comparing the experimental and calculated data.     

Measurements and modeling of quaternary (liquid + liquid) equilibria for mixtures of (methanol or ethanol + water + toluene + n-dodecane)

The extraction of aromatic compound toluene from alkane, dodecane, by mixed solvents (water + methanol), (water + ethanol) and (methanol + ethanol) have been studied by (liquid + liquid) equilibrium (LLE) measurements at three temperatures (298.15, 303.15, and 313.15) K and ambient pressure. The compositions of liquid phases at equilibrium were determined by gas liquid chromatography.The experimental tie-line data for three quaternary mixtures of {(water + methanol) + toluene + dodecane}, {(water + ethanol) + toluene + dodecane}, and {(methanol + ethanol) + toluene + dodecane} are presented. The experimental quaternary LLE data have been satisfactorily correlated by using the UNIQUAC and NRTL activity coefficient models. The parameters of the models have been evaluated and presented. The tie-line data of the studied quaternary mixtures also were correlated using the Hand method. The partition coefficients and the selectivity factor of solvent are calculated and compared for the three mixed solvents.The comparisons indicate that the selectivity factor for mixed solvent (methanol + ethanol) is higher than the other two mixed solvents at the three studied temperatures. However, considering the temperature variations of partition coefficients of toluene in two liquid phases at equilibrium, an optimum temperature may be obtained for an efficient extraction of toluene from dodecane by the mixed solvents.     

(Liquid + liquid) equilibria of [C8mim][NTf2] ionic liquid with a sulfur-component and hydrocarbons

(Liquid + liquid) equilibrium (LLE) data for {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + n-dodecane} and {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + cyclohexane} ternary systems have been determined experimentally at 298.15 K. The compositions of the tie-lines ends have been obtained by gas chromatographic analysis of phases at equilibrium, being distribution coefficients and separation factors calculated from them. The experimental results have been correlated by means of the NRTL model but considerable deviations from experimental data were found.     

Experimental and theoretical study of quaternary (liquid + liquid) equilibria for mixtures of (methanol or water + ethanol + toluene + n-decane)

Experimental (liquid + liquid) equilibrium data were obtained for the extraction of toluene from n-decane by mixed-solvents (ethanol + water) and (ethanol + methanol) at three temperatures (298.15, 303.15, and 313.15) K and ambient pressure.The measured tie-line data for two quaternary mixtures of {(ethanol +  water) + toluene + n-decane} and {(ethanol + methanol) + toluene + n-decane} are presented. The experimental quaternary (liquid + liquid) equilibrium data have been correlated using the NRTL activity coefficient model to obtain the binary interaction parameters of these components. The NRTL models predict the equilibrium compositions of the quaternary mixtures with small deviations. The partition coefficients and the selectivity factor of the mixed-solvents used were calculated and presented. From our experimental and calculated results, we conclude that for the extraction of toluene from n-decane mixtures the mixed-solvent (ethanol + methanol) has a higher selectivity factor than the other mixed-solvent at the three temperatures studied.     

Thermodynamic study of the system (LiCl + CaCl2 + H2O)

Solubility isotherms of the ternary system (LiCl + CaCl₂ + H₂O) were elaborately determined at T = (283.15 and 323.15) K. Several thermodynamic models were applied to represent the thermodynamic properties of this system. By comparing the predicted and experimental water activities in the ternary system, an empirical modified BET model was selected to represent the thermodynamic properties of this system. The solubility data determined in this work at T = (283.15 and 323.15) K, as well as those from the literature at other temperatures, were used for the model parameterization. A complete phase diagram of the ternary system was predicted over the temperature range from (273.15 to 323.15) K. Subsequently, the Gibbs free energy of formation of the solid phases CaCl₂ · 4 H₂O_(s), CaCl₂ · 2 H₂O_(s), LiCl · 2H₂O_(s), and LiCl · CaCl₂ · 5H₂O_(s) was estimated and compared with the literature data.     

Ternary (liquid + liquid) equilibria of {trifluorotris(perfluoroethyl)phosphate based ionic liquids + thiophene + heptane}

Ternary (liquid + liquid) equilibria for three systems containing ionic liquids {(4-(2-methoxyethyl)-4-methylmorpholinium trifluorotris(perfluoroethyl)phosphate, 1-(2-methoxyethyl)-1-methylpiperidinium trifluorotris(perfluoroethyl)phosphate, 1-(2-methoxyethyl)-1-methylpyrrolidinium trifluorotris(perfluoroethyl)phosphate) + thiophene + heptane} have been determined at T = 298.15 K. All systems showed high solubility of thiophene in the ionic liquid and low solubility of heptane. The solute distribution coefficient and the selectivity were calculated for all systems. High values of selectivity were obtained. The experimental results have been correlated using NRTL model. The influence of ionic liquid structure on phase equilibria is discussed.     

(Liquid + liquid) equilibrium of (NaNO3 + PEG 4000 + H2O) ternary system at different temperatures

Phase diagram and (liquid + liquid) equilibrium (LLE) data for the (NaNO₃ + polyethylene glycol 4000 (PEG 4000) + H₂O) system have been determined experimentally at T = (288.15 and 308.15) K. The effects of temperature on the binodal curves and tie-lines have been studied and it was found that an increasing in temperature caused the expansion of two-phase region. The Chen-NRTL, modified Wilson and UNIQUAC models were used to correlate the experimental tie-line data. The results show that the quality of fitting is better with the UNIQUAC model.     

(Liquid + liquid) equilibrium of (NaClO4 + PEG 4000 + H2O) ternary system at different temperatures

Phase diagram and (liquid + liquid) equilibrium (LLE) results for {NaClO₄ + polyethylene glycol 4000 (PEG 4000) + H₂O} have been determined experimentally at T = (288.15, 298.15, and 308.15) K. The Chen-NRTL, modified Wilson and UNIQUAC models were used to correlate the values for the experimental tie-lines. The results show that the quality of fitting is better with the modified Wilson model.     

Thermodynamic study of the system (LiCl + LiNO3 + H2O)

The solubility of the binary system (LiNO₃ + H₂O) from T = 273.15 K to T = 333.15 K and solubility isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were elaborately measured at T = 273.15 K and T = 323.15 K. These solubility data, as well as water activities in the binary systems from the literature, were treated by an empirically modified BET model. The isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were reproduced and a complete phase diagram of the ternary system in the temperature range from 273.15 K to 323.15 K predicted. It is shown that the solubility data for the binary system (LiNO₃ + H₂O) measured in this work are slightly different from the literature data. Simulated results showed that the saturated salt solution of (2.8LiCl + LiNO₃) is in equilibrium with the stable solid phase LiNO₃(s) over the temperature range from 283.15 K to 323.15 K, other than the solid phases LiNO₃ · 3H₂O(s) and LiClH₂O(s) as reported by Iyoki et al. [S. Iwasaki, Y. Kuriyama. T. Uemura, J. Chem. Eng. Data 38 (1993) 396–398].     

(Liquid + liquid) equilibria for the ternary mixtures (alkane + toluene + ionic liquid) at T = 298.15 K: Influence of the anion on the phase equilibria

(Liquid + liquid) equilibrium data for the ionic liquids 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMpyr][NTf₂], and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, [BMpyr][TFO], with toluene, and heptane or cyclohexane were determined at T = 298.15 K and atmospheric pressure. In order to check if these ILs can be used as potential solvents for the extraction of toluene from aliphatic compounds, the ability of the ILs as solvents was evaluated in terms of selectivity and solute distribution ratio. The experimental data were correlated accurately with the Non Random Two-Liquid model.     

Simultaneous solubility of SO2 and NH3 in (salt + H2O) and enthalpy change upon dilution of (SO2 + NH3 + salt + H2O) in (salt + H2O) {salt = (NH4)2SO4 or Na2SO4}: Experimental results and model predictions

The simultaneous solubility of sulfur dioxide and ammonia in aqueous solutions of (ammonium sulfate or sodium sulfate) was measured by a synthetic method in the temperature range from 313.6 to 373.2 K and at pressures up to 2.5 MPa. Furthermore, the enthalpy change upon diluting aqueous solutions of sulfur dioxide, ammonia and (ammonium sulfate or sodium sulfate) in aqueous solutions of the same salt was measured in a batch calorimeter at about 313 and 352 K. The experimental results are used for comparison with predictions from a thermodynamic model for the vapor–liquid equilibrium and the enthalpy of dilution of those chemical reacting systems. In that model, activity coefficients are calculated from Pitzer's molality-scale-based Gibbs excess energy model, where all interaction parameters are either adopted from previous investigations on the properties of the binary and ternary sub-systems (if available) or they are neglected (if they are not available).     

(Liquid + liquid) equilibrium for ternary mixtures of {heptane + aromatic compounds + [EMpy][ESO4]} at T = 298.15 K

(Liquid + liquid) equilibrium (LLE) data for the ternary systems (heptane + toluene + 1-ethyl-3-methylpyridinium ethylsulfate) and (heptane  + benzene + 1-ethyl-3-methylpyridinium ethylsulfate) were measured at T = 298.15 K and atmospheric pressure. The selectivity and aromatic distribution coefficients, calculated from the equilibrium data, were used to determine if this ionic liquid can be used as a potential extracting solvent for the separation of aromatic compounds from heptane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations.     

Isopiestic studies on the saturated systems {H2O + BaCl2(sat) + NaCl + NH4Cl} and {H2O + BaCl2(sat) + mannitol(sat) + NaCl + NH4Cl} at the temperature 298.15 K: Comparison with the ideal-like solution model

Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated aqueous solutions: {H₂O + BaCl₂(sat) + NaCl + NH₄Cl} saturated with barium chloride and {H₂O + BaCl₂(sat) + mannitol(sat) + NaCl + NH₄Cl} saturated with barium chloride and mannitol. Taking sodium chloride (aq) as reference solutions, osmotic coefficients of the aqueous solutions were determined. The experimental results are well represented by the ideal-like solution model.     

Modeling of the quaternary NaCl + KCl + CH3OH + H2O mixed electrolyte system: Binary and ternary mixing (ion + ion) and (ion + nonelectrolyte) interaction parameters

The purpose of this work is modeling of the quaternary system of mixed NaCl + KCl electrolyte in mixed CH₃OH + H₂O solvent, with different alcohol mass fractions by using particularly, the Pitzer (P) and Pitzer–Esteso (PE) equations and based on potentiometric measurement technique. The experimental data are obtained by different molal salt ratio r (r = m_NaCl/m_KCl = 100, 150, 200 and 250) in mixed solvent with different alcohol mass fractions x (x = 0.10, 0.20, 0.30, 0.40, and 0.50) in water. A galvanic cell is employed for collecting the potentiometric data by combining a Na⁺ glass membrane and Ag/AgCl electrodes and using different series of electrolyte solutions, at defined constant ionic strengths, with the molality ranging from 0.0005 up to 3.5 mol · kg⁻¹, at T = 298.15 ± 0.05 K of experiments. Comparison of the models shows that the modified Pitzer equation by Esteso (PE) present a better fit of the experimental data.