Simulation of the (vapor + liquid) equilibria of binary mixtures of benzene,cyclohexane, and hydrogen

Molecular simulations of the (vapor + liquid) equilibria (VLE) for benzene, cyclohexane, and (benzene + hydrogen) and (cyclohexane + hydrogen) were carried out using the Gibbs-ensemble Monte Carlo method with configurational bias. The Buckingham exponential six (exp-6) potential was used for the site–site interactions with no binary interaction parameters; benzene and cyclohexane were described with six interaction sites, and hydrogen with a single site. Simulation results, density, pressure, and vaporization enthalpy for benzene and cyclohexane were in reasonable agreement with experimental data, but critical pressures obtained from extrapolation of the VLE results did not match the experimental values. For (benzene + hydrogen) and (cyclohexane + hydrogen) mixtures mole fractions from simulation were compared with experimental data, the results for liquid phase were in closer agreement with experiment than the results for vapor phase. For the mixtures, results from the PSRK equation of state (PSRK-EOS) predicted the mole fractions for both phases, also vapor densities from molecular simulation were in close agreement with PSRK-EOS. Additionally, the Henry’s law constant (K_H) for hydrogen was calculated in separate simulations using test particle insertions, and qualitative agreement with values from experimental VLE data was obtained. For the (benzene + hydrogen) system K_H results from PSRK-EOS were closer to experiment than the results from simulation, but, for the (cyclohexane + hydrogen) system results from both methods had similar deviations from experiment. The results for pure substance and mixtures indicate that the combination of the three molecular models used for benzene, cyclohexane, and hydrogen is valid for the simulation of the VLE of their mixtures.     

Isobaric vapor–liquid and vapor–liquid–liquid equilibrium data for the system water + ethanol + cyclohexane

Isobaric vapor–liquid (VLE) and vapor–liquid–liquid equilibria (VLLE) were measured for the ternary system water + ethanol + cyclohexane at 101.3 kPa. The experimental determination was carried out in a dynamic equilibrium still with circulation of both the vapor and liquid phases, equipped with an ultrasonic homogenizer. The experimental data demonstrated the existence of a ternary heterogeneous azeotrope at 335.6 K with a composition of 0.188, 0.292, 0.520 mole fraction of water, ethanol and cyclohexane, respectively. The experimental data were compared with those obtained using UNIFAC and NRTL models with parameters taken from literature.     

Evaluation of the ionic liquids 1-alkyl-3-methylimidazolium hexafluorophosphate as a solvent for the extraction of benzene from cyclohexane: (Liquid + liquid) equilibria

In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid + liquid) equilibrium of 1-alkyl-3-methylimidazolium hexafluorophosphate, [C_nmim][PF₆] (n = 4, 5, 6), with benzene and cyclohexane was studied at T = 298.15 K and atmospheric pressure. The reliability of the experimentally determined tie-line data was confirmed by applying the Othmer–Tobias equation. The solute distribution coefficient and solvent selectivity for the systems studied were calculated and compared with literature data for other ILs and sulfolane. It turns out that the benzene distribution coefficient increases and solvent selectivity decreases as the length of the cation alkyl chain grows, and the ionic liquids [C_nmim][PF₆] proved to be promising solvents for benzene–cyclohexane extractive separation. Finally, an NRTL model was applied to correlate and fit the experimental LLE data for the ternary systems studied.     

Isobaric vapor–liquid equilibrium for methyltrichlorosilane–dimethyldichlorosilane–benzene system

Isobaric vapor–liquid equilibrium (VLE) for the system methyltrichlorosilane–dimethyldichlorosilane–benzene and that of the three binary systems were measured with a new pump-ebulliometer at the pressure of 101.325 kPa. These binary compositions of the equilibrium vapor were calculated according to the Q function of molar excess Gibbs energy by the indirect method and the resulted VLE data agreed well with the thermodynamic consistency. Moreover, the experimental data were correlated with the Wilson, NRTL, Margules and van Laar equations by means of the least-squares fit, the acquired optimal interaction parameters were fitted to experimental vapor–liquid equilibrium data for binary systems. The binary parameters of Wilson equation were also used to calculate the bubble point temperature and the vapor phase composition for the ternary mixtures without any additional adjustment. The predicted vapor–liquid equilibrium for the ternary system accorded well with the experimental results. The separation factor of methyltrichlorosilane against dimethyldichlorosilane in benzene was also reported. The VLE of binary and multilateral systems provided essential theory for the production of the halogenated silane.     

(Vapour + liquid) equilibria of ternary systems with ionic liquids using headspace gas chromatography

(Vapour + liquid) equilibrium (VLE) data for the ternary systems (hexane + benzene), (hexane + cyclohexane), (benzene + cyclohexane), and (ethanol + water) with an ionic liquid as entrainer for extractive distillation were measured by headspace gas chromatography. As ionic liquids, 1-hexyl-3-methyl-imidazolium bis (trifluoromethyl-sulfonyl) imide [HMIM][BTI], 1-octyl-3-methyl-imidazolium bis (trifluoromethyl-sulfonyl) imide [OMIM][BTI], 1-octyl-3-methyl-imidazolium trifluoro-methanesulfonate [OMIM][OTF], and 1-butyl-3-methyl-imidazolium trifluoro-methanesulfonate [BMIM][OTF] were used. The experimental data show that the ionic liquids investigated have a great influence on the separation factors of the systems (hexane + benzene), (hexane + cyclohexane), and (benzene + cyclohexane). The experimental data were compared with the predicted results using mod. UNIFAC (Do). The predicted results are in good agreement with the experimental data.     

Isobaric vapor–liquid equilibria for mixtures of acetone,ethanol, and 2,2,4-trimethylpentane at 101.3 kPa

Isobaric vapor–liquid equilibrium (VLE) data were determined at the pressure of 101.3 kPa for binary and ternary systems composed of acetone, ethanol, and 2,2,4-trimethylpentane (isooctane). Minimum boiling azeotropes were found in the acetone + 2,2,4-trimethylpentane and ethanol + 2,2,4-trimethylpentane systems. Azeotropic behavior was not found for the ternary system. Thermodynamic consistency tests were performed for all VLE data. The activity coefficients of the binary mixtures were satisfactorily correlated as function of the mole fraction using the Wilson, NRTL, and UNIQUAC models. The models with their best-fitted parameters were used to predict the ternary vapor–liquid equilibrium. The Wilson model appears to yield the best prediction in boiling temperatures.     

(Liquid + liquid) equilibria for mixtures of (ethylene glycol + benzene + cyclohexane) at temperatures (298.15, 308.15, and 318.15) K

Experimental (liquid + liquid) equilibrium (LLE) data for a ternary system containing (ethylene glycol + benzene + cyclohexane) were determined at temperatures (298.15, 308.15, and 318.15) K and at atmospheric pressure. The experimental distribution coefficients and selectivity factors are presented to evaluate the efficiency of the solvent for extraction of benzene from cyclohexane. The effect of temperature in extraction of benzene from the (benzene + cyclohexane) mixture indicated that at lower temperatures the selectivity (S) is higher, but the distribution coefficient (K) is rather lower. The LLE results for the system studied were used to obtain binary interaction parameters in the UNIQUAC and NRTL models by minimizing the root mean square deviations (RMSD) between the experimental results and calculated results. Using the interaction parameters obtained, the phase equilibria in the systems were calculated and plotted. The NRTL model fits the (liquid + liquid) equilibrium data of the mixture studied slightly better. The root mean square deviations (RMSDs) obtained comparing calculated and experimental two-phase compositions are 0.92% for the NRTL model and 0.95% for the UNIQUAC model.     

Isothermal vapor–liquid equilibria and excess molar volumes for the ternary mixtures containing 2-methyl pyrazine

Isothermal vapor–liquid equilibrium (VLE) data at 353.15 K and excess molar volumes (V^E) at 298.15 K are reported for the binary systems of ethyl acetate (EA)+cyclohexane and EA+n-hexane and also for the ternary systems of EA+cyclohexane+2-methyl pyrazine (2MP) and EA+n-hexane+2MP. The experimental binary VLE data were correlated with common g^E model equations. The correlated Wilson parameters of the constituent binary systems were used to calculate the phase behavior of the ternary mixtures. The calculated ternary VLE data using Wilson parameters were compared with experimental ternary data. The experimental excess molar volumes were correlated with the Redlich–Kister equation for the binary mixtures, and Cibulka’s equation for the ternary mixtures.     

Phase equilibria properties of binary and ternary systems containing di-isopropyl ether + isobutanol + benzene at 313.15 K

Isothermal vapour–liquid equilibrium data have been measured for the ternary system (di-isopropyl ether + isobutanol + benzene) and two of the binary systems involved (di-isopropyl ether + isobutanol) and (isobutanol + benzene) at 313.15 K. A static technique consisting of an isothermal total pressure cell was used for the measurements. Data reduction by Barker's method provides correlations for G^E using the Margules equation for the binary systems and the Wohl expansion for the ternary system. Wilson, NRTL and UNIQUAC models have been applied successfully to both the binary and the ternary systems.     

Quaternary (liquid + liquid) equilibrium data for the extraction of toluene from alkanes using the ionic liquid [EMim][MSO4]

(Liquid + liquid) equilibrium (LLE) studies for the extraction of aromatics from alkanes present in the petroleum fractions are important to develop theoretical/semiempirical (liquid + liquid) equilibrium models, which are used in the design of extraction processes. In this work, the ionic liquid 1-ethyl-3-methylimidazolium methylsulfate, [EMim][MSO₄], was evaluated as potential solvent for the separation of toluene from heptane and cyclohexane. The LLE data for the quaternary system {heptane (1) + cyclohexane (2) + toluene (3) + [EMim][MSO₄] (4)} were experimentally determined at T = 298.15 K and atmospheric pressure. Moreover, the LLE data for the ternary systems {heptane or cyclohexane (1) + toluene (2) + [EMim][MSO₄] (3)} were also determined. Solute distribution ratios and selectivities were calculated and analysed in order to evaluate the capability of the ionic liquid to accomplish the separation target. A comparison between the solute distribution ratios and selectivities for the quaternary and the ternary systems was also made. Finally, the experimental tie-line data were correlated with the NRTL model.     

Measurement of (liquid + liquid) equilibria for ternary systems of (N-formylmorpholine + benzene + cyclohexane) at temperatures (303.15, 308.15, and 313.15) K

This work demonstrates the ability of N-formylmorpholine (NFM) to act as an extraction solvent for the removal of benzene from its mixture with cyclohexane. The (liquid + liquid) equilibria (LLE) were measured for a ternary system of {N-formylmorpholine (NFM) + benzene + cyclohexane} under atmospheric pressure and at temperatures (303.15, 308.15, and 313.15) K. The experimental distribution coefficients (K) and selectivity factors (S) were obtained to reveal the extractive effectiveness of the solvent for separation of benzene from cyclohexane. The LLE results for the system studied indicate that increasing temperature decreases selectivity of the solvent. The reliability of the experimental results was tested by applying the Othmer–Tobias correlation. In addition, the universal quasichemical activity coefficient (UNIQUAC) and the non-random two liquids equation (NRTL) were used to correlate the LLE data using the interaction parameters determined from the experimental data. The root mean square deviations (RMSDs) obtained comparing calculated and experimental two-phase compositions are 0.0367 for the NRTL model and 0.0539 for the UNIQUAC model.     

Isobaric vapor–liquid equilibria for 1-propanol + water + copper(II) chloride at 100 kPa

Isobaric vapor–liquid equilibria for the ternary system 1-propanol + water + copper(II) chloride has been measured at 100 kPa using a recirculating still. The addition of copper(II) chloride to the solvent mixture produced a salting-out effect of the alcohol, but the azeotrope did not tend to be eliminated when the salt content increased. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of Mock's model were estimated. This model has proved to be suitable to represent experimental data in the entire range of compositions. The effect of copper(II) chloride on the vapor–liquid equilibrium of the 1-propanol + water system has been compared with that produced by other salts.     

(Liquid + liquid) equilibrium data for the ternary systems (cycloalkane + ethylbenzene + 1-ethyl-3-methylimidazolim ethylsulfate) at T = 298.15 K and atmospheric pressure

In this paper, (liquid + liquid) equilibrium (LLE) data for the ternary systems (cyclohexane, or cyclooctane, or methylcyclohexane + ethylbenzene + 1-ethyl-3-methylimidazolium ethylsulfate) have been determined experimentally at T = 298.15 K and atmospheric pressure. The solubility curves and the tie-line compositions of the conjugate phases were obtained by means of density. The degree of consistency of the tie-lines was tested using the Othmer–Tobias equation, and the Non-Random Two-Liquid (NRTL) and the Universal Quasi-Chemical (UNIQUAC) models were used to correlate the phase equilibrium in the systems. Selectivity and solute distribution ratio were evaluated for the immiscible region.     

Vapor–liquid equilibrium of methane and methane + nitrogen and an equimolar hexane + decane mixture under isothermal conditions

Experimental vapor–liquid equilibrium data of the ternary system composed of methane and an equimolar hexane + decane mixture are reported. The experimental measurements were carried out under isothermal conditions at 258, 273, and 298 K in the pressure range 1–19 MPa. Also, experimental vapor–liquid measurements were carried out for the quaternary system methane + nitrogen and an equimolar hexane + decane mixture, at 258 K in the range 3.5–12 MPa. The results for the ternary system show that the solubility of methane in the equimolar mixture of alkanes increases when the pressure is increased at constant temperature and it increases as the temperature decreases in the whole pressure range studied. For the quaternary system with a constant amount of nitrogen, the solubility of methane in the liquid phase increases as the pressure increases at the studied temperature. The experimental results for the ternary system were satisfactorily correlated with the Peng–Robinson equation of state in the ranges of pressure and temperature studied. The equation of state was used to predict the behavior of the quaternary system using binary interaction parameters. The applicability of the principle of congruence was corroborated by comparing the vapor–liquid behavior of methane in the equimolar hexane + decane mixture with that in pure octane, at the three temperatures studied in this work.     

Separation of benzene from alkanes using 1-ethyl-3-methylpyridinium ethylsulfate ionic liquid at several temperatures and atmospheric pressure: Effect of the size of the aliphatic hydrocarbons

The ionic liquid 1-ethyl-3-methylpyridinium ethylsulfate, [EMpy][ESO₄], was studied for the separation of benzene from aliphatic hydrocarbons (octane or nonane) by solvent extraction through the determination of the (liquid + liquid) equilibrium (LLE) of the ternary systems: {octane (1) + benzene (2) + [EMpy][ESO₄] (3)} and {nonane (1) + benzene (2) + [EMpy][ESO₄] (3)} at T = (283.15 and 298.15) K and atmospheric pressure. Binodal curves were determined using the “cloud point” method, and tie-line compositions were obtained by density measurements. The values of selectivity and distribution coefficient, derived from the tie-line data, were used to decide if this ionic liquid can be used as potential solvent for the separation of benzene from aliphatic hydrocarbons using liquid extraction. These results were analyzed and compared to those previously reported for the systems {hexane + benzene + [EMpy][ESO₄]} and {heptane + benzene + [EMpy][ESO₄]}. The experimental results show that this ionic liquid is suitable for the extraction of benzene from mixtures containing octane and nonane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. The experimental results for the ternary systems were well correlated with the NRTL model. No literature data were found for the mixtures discussed in this paper.     

Study of activity coefficients for sodium iodide in (methanol + benzene) system by (vapour + liquid) equilibrium measurements

By measuring the (vapour + liquid) equilibrium of {methanol (1) + benzene (2) + NaI} and testing the data using the ternary Gibbs–Duhem equation, the experimental results of the (vapour + liquid) equilibrium with thermodynamic consistency are obtained. It is supposed that the mean activity coefficients of NaI in (methanol + benzene) mixed solvents may be represented by a power series of salt concentration (m^1/2). Each parameter of the series was then obtained from the experimental results by the method of least squares. The calculated results show that the activity coefficients of NaI in (methanol + benzene) system with constant composition either decrease as the concentration increases, or decrease at first, then pass through a minimum and increase gradually again. This method is applicable to the determination of electrolytic activity coefficients in mixed non-aqueous solvents.     

(Liquid + liquid) equilibria in ternary aqueous mixtures of phosphoric acid with organic solvents at T = 298.2 K

(Liquid + liquid) equilibrium (LLE) data for the ternary mixtures of {water (1) + phosphoric acid (2) + organic solvents (3)} were determined at T = 298.2 K and atmospheric pressure. The organic solvents were cyclohexane, 2-methyl-2-butanol (tert-amyl alcohol), and isobutyl acetate. All the investigated systems exhibit Type-1 behaviour of LLE. The immiscibility region was found to be larger for the (water + phosphoric acid + cyclohexane) ternary system. The experimental LLE results were correlated with the NRTL model, and the binary interaction parameters were obtained. The reliability of the experimental tie-line results was tested through the Othmer–Tobias and Bachman correlation equations. Distribution coefficients and separation factors were evaluated over the immiscibility regions and a comparison of the extracting capabilities of the solvents was made with respect to these factors. The experimental results indicate the superiority of cyclohexane as the preferred solvent for the extraction of phosphoric acid from its aqueous solutions.     

Thermodynamics of organic mixtures containing amines. X. Phase equilibria for binary systems formed by imidazoles and hydrocarbons: Experimental data and modelling using DISQUAC

(Solid + liquid) equilibrium (SLE) temperatures have been determined using a dynamic method for the systems (1H-imidazole, + benzene, + toluene, + hexane, or + cyclohexane; 1-methylimidazole + benzene, or + toluene, 2-methyl-1H-imidazole + benzene, + toluene, or + cyclohexane, and benzimidazole + benzene). In addition (liquid + liquid) equilibrium (LLE) temperatures have been obtained using a cloud point method for (1H-imidazole, + hexane, or + cyclohexane; 1-methylimidazole + toluene, and 2-methyl-1H-imidazole + cyclohexane). The measured systems show positive deviations from the Raoult’s law, due to strong dipolar interactions between amine molecules related to the high dipole moment of imidazoles. On the other hand, DISQUAC interaction parameters for the contacts present in these solutions and for the amine/hydroxyl contacts in (1H-imidazole + 1-alkanol) mixtures have been determined. The model correctly represents the available data for the examined systems. Deviations between experimental and calculated SLE temperatures are similar to those obtained using the Wilson or NRTL equations, or the UNIQUAC association solution model. The quasichemical interaction parameters are the same for mixtures containing 1H-imidazole, 1-methylimidazole, or 2-methyl-1H-imidazole and hydrocarbons. This may be interpreted assuming that they are members of a homologous series. Benzimidazole behaves differently.     

Vapor–liquid equilibria for the ternary mixture of carbon dioxide + 1-propanol + propyl acetate at elevated pressures

Vapor–liquid equilibrium (VLE) data for the ternary mixture of carbon dioxide, 1-propanol and propyl acetate were measured in this study at 308.2, 313.2, and 318.2 K, and at pressures ranging from 4 to 10 MPa. A static type phase equilibrium apparatus with visual sapphire windows was used in the experimental measurements. New VLE data for CO₂ in the mixed solvent were presented. These ternary VLE data at elevated pressures were also correlated using either the modified Soave–Redlich–Kwong or Peng–Robinson equation of state (EOS), and by employing either the van der Waals one-fluid or Huron–Vidal mixing model. Satisfactory correlation results from both EOS models are reported with temperature-independent binary interaction parameters. It is observed that at 318.2 K and 10 MPa, 1-propanol may probably be separated from propyl acetate into the vapor phase at the entire concentration range in the presence of high pressure CO₂.     

Quaternary isobaric (vapor + liquid + liquid) equilibrium and (vapor + liquid) equilibrium for the system (water + ethanol + cyclohexane + heptane) at 101.3 kPa

Experimental isobaric (vapor + liquid + liquid) and (vapor + liquid) equilibrium data for the ternary system {water (1) + cyclohexane (2) + heptane (3)} and the quaternary system {water (1) + ethanol (2) + cyclohexane (3) + heptane (4)} were measured at 101.3 kPa. An all-glass, dynamic recirculating still equipped with an ultrasonic homogenizer was used to determine the VLLE. The results obtained show that the system does not present quaternary azeotropes. The point-by-point method by Wisniak for testing the thermodynamic consistency of isobaric measurements was used to test the equilibrium data.