UNIQUAC Models Research Articles

Vapour–liquid equilibrium and extractive distillation for separation of azeotrope isopropyl alcohol and diisopropyl ether

For separation of the azeotrope isopropyl alcohol and diisopropyl ether by extractive distillation, 2-ethoxyethanol and butyl acetate were adopted as extractive solvents, and the vapour–liquid equilibrium data for the binary systems of isopropyl alcohol + 2-ethoxyethanol, isopropyl alcohol + butyl acetate, diisopropyl ether + 2-ethoxyethanol and diisopropyl ether + butyl acetate were measured at 101.3 kPa by a modified Rose type recirculating still. The Herington and van Ness consistency method were used to check the thermodynamic consistency of the VLE data. Meanwhile, the VLE data were correlated using the NRTL, UNIQUAC and Wilson models, and the binary interaction parameters of the three models were regressed. The correlation results indicate that the three models can correlate the experimental data with the root-mean-square deviation value of vapour phase mole faction less than 0.0062. Finally, an extractive distillation process for separating the azeotrope of isopropyl alcohol and diisopropyl ether is explored in this work.

Solubility of Syngas Components in Water, Acetic Acid, and Alcohol Using New Standard Fugacity Methodology

The UNIQUAC model in combination with the Peng–Robinson and the Hayden–O’Connell Virial equation of state was used for correlating vapor–liquid equilibrium for a gas–solvent system containing the following: CO2–water, CO2–ethanol, CO2–acetic acid, CO–water, CO–ethanol, CO–acetic acid, CH4–water, CH4–ethanol, CH4–acetic acid, N2–water, N2–ethanol, N2–acetic acid, H2–water, and H2–ethanol. Prausnitz and Shair correlation, for the fugacity of the hypothetical liquid solute at a pressure of 1 atm, was implemented in the parametrization procedure as additional objective function so as to reduce the uncertainty on the constants of the model. The results show that the UNIQUAC equation, coupled with an appropriate equation of state to model the vapor phase nonideality, is able to represent the binaries in the range of temperatures and pressures considered in the study, i.e., from 0 to 310 °C and from 1 to 400 bar, respectively. In addition to model parameter estimation, a new generic method to evaluate gas solubi...

Influence of the temperature on the equilibrium phase diagram of the ternary system water + ammonium chloride + 2-propanol at 101.3 kPa

The phase equilibrium of the water + NH4Cl + 2-propanol mixture, at a constant pressure of 101.3 kPa, has been determined isothermally at four temperatures, as well as at the boiling temperature. Transitions between the different regions of the isothermal equilibrium diagrams have been studied, and the lowest temperature at which the salt can split water + 2-propanol mixtures into two liquid phases, is found to be 310.1 K. As the temperature is increased from this critical value, the two-liquid-phase region expands until the boiling temperature is reached.Finally, the extended UNIQUAC model for electrolytes has been used to predict the equilibrium diagram of the system. Large discrepancies with the experimental results have been found, and it will, therefore, be necessary to review the parameters of the model based on the experimental data reported in this work.

Isothermal Vapor–Liquid Equilibrium Measurements of Butan-2-one + 2-Methyl-propan-1-ol/Pentan-1-ol

Isothermal vapor–liquid equilibrium (VLE) data were measured for the systems of butan-2-one (1) + 2-methyl-propan-1-ol (2)/pentan-1-ol (2) using a dynamic low-pressure apparatus. Measurements were undertaken at approximately 333, 343, and 348 K. The VLE data were correlated by minimizing the pressure residual using the combined method with the Wilson and UNIQUAC activity coefficient models being employed for the liquid phase nonideality, using the virial equation of state with the Hayden and O’Connell correlation for the vapor phase nonideality. The Wilson model provided a marginally superior fit of the VLE data to the UNIQUAC model. The thermodynamic consistency of the data was tested, and it was found that all data sets were thermodynamically consistent according to the area and point tests. Excess enthalpies were calculated from the modeled VLE data and were extrapolated to conditions of experimental data from the literature. A good correlation was found between the experimental literature and calculat...

Liquid–Liquid Equilibrium Study in the n-Heptane + Phenol + Sulfolane Ternary System

Liquid–liquid equilibrium data for the n-heptane + phenol + sulfolane system were obtained at 323.15 and 343.15 K under 101.35 kPa pressure. The distribution coefficient (K) and separation factor (S) were calculated to assess the effectiveness of extracting phenol from n-heptane, and the consistency of LLE date were verified by the Othmer–Tobias, Hand as well as Bachman equations. The experimental data were correlated by using NRTL and UNIQUAC models, and the root-mean-square deviation (RMSD) values of both models were below 0.59%, demonstrating the two models were successfully describe the experimental data.

Study of phase behavior of 2,6-lutidine, 2,6-lutidine-N-oxide and water mixture using UNIQUAC model with interaction parameters determined by molecular simulations

The study of the liquid-liquid equilibrium (LLE) between 2,6-lutidine, 2,6-lutidine-N-oxide and water is important since it has the potential to influence the overall rate of the N-oxidation reaction involving these chemicals. The hydrogen peroxide, which is used as an oxidant to convert the lutidine into N-oxide, decomposes vigorously in a phase separated mixture affecting the overall safety of the process. In the current work, the UNIQUAC activity coefficient model was used to estimate the biphasic compositions and predict the LLE curve for the ternary mixture. The energy parameters used in the equations, which describe the intermolecular interactions were calculated based on molecular simulations. Apart from this, the molecular parameters for N-oxide were obtained by following a quantum mechanical approach, which utilized the GEPOL algorithm to construct the molecular surface. The results predicted by the model provide a satisfactory representation of experimental data at T = 383 K. In addition to this, the influence of temperature on the phase behavior was studied by generating phase equilibrium data at T = 373 and 398 K.

Thermodynamic equilibrium study of phosphorus pentoxide-water binary system: The stability and solubility of 10H3PO4.H2O

In this study, new experimental data for the binary system of water–phosphorus pentoxide are presented in the temperature range from 235.15 to 302.15 K using the conductimetric method, this synthetic method was successfully and effectively used to define the branches of stable solubility of several complex systems. In this work, two hydrates 2H3PO4·H2O (semi-hydrate) and 10H3PO4.H2O (deci-hydrate) were identified and characterized by X ray diffraction and volumetric titration with discussion of their stability zone. Thermodynamic modeling of solid-liquid equilibrium in the binary system of P2O5–H2O is also presented based on this experimental solubility data using a modified electrolytic Uniquac model (Extended Universal Quasichimical model).

Experimental and predicted vapor–liquid equilibrium for binary systems with diethanolamine, m-cresol and p-cresol at 20.0 kPa

Isobaric vapour–liquid equilibrium (VLE) data for two binary systems of p-Cresol (PC) + diethanolamine (DEA) and m-Cresol (MC) + DEA were measured at 20.0 kPa. The Herington area method was used to check the binary VLE data, and the results showed good thermodynamic consistency. Meanwhile, the Wilson, NRTL, UNIQUAC models and the chemistry theory proposed by Dolezalek were used to correlate the VLE data. The binary energy interaction parameters for activity models, and reaction equilibrium constants for chemistry theory were obtained. With help of the parameters obtained in this work, the NRTL model was used to predict the VLE data of the two binary systems at the pressure of 8.33 kPa. The predictive results were compared with the literature’s data. At same time, the excess Gibbs free energy for the two binary systems, and infinite dilution activity coefficients for MC and PC in DEA were estimated. The calculated results showed that the DEA had slightly stronger interaction with PC than MC.

Liquid-liquid equilibrium for mixtures of hexadecane + xylenes + pyrene + solvent at 373.15 K

Liquid-liquid equilibrium tie line data were determined at 373.15 K for a model hydrocarbon mixture consisting of hexadecane + xylenes + pyrene with the solvents sulfolane and diethylene glycol (DEG), and also with the solvent combination N-methylpyrrolidone/ethylene glycol (NMP/EG). The measured data were used to estimate binary interaction parameters of the UNIQUAC model. All solvents presented comparable selectivities for pyrene relative to xylenes. Pyrene partition ratios greater than unity were observed for sulfolane only. As a result, from a selectivity/capacity viewpoint, when compared to NMP/EG and DEG, sulfolane is potentially the best suited solvent for extraction of pyrene. Selectivities greater than unity were observed for all solvents studied. Therefore, pyrene, a polycyclic aromatic hydrocarbon, can be selectively removed from oil containing monocyclic aromatic hydrocarbons such as xylenes.

Solvent screening and liquid-liquid measurement for extraction of phenols from aromatic hydrocarbon mixtures

The separation of phenolic compounds from low temperature coal tar has great significance for further application of the coal tar. In this paper, the separation of special phenolic compounds from model coal tar (phenols + toluene) was studied. The universal quasi chemical functional group activity coefficient (UNIFAC) and conductor-like screening model COSMO-SAC (segment activity coefficient) was carried out to screen suitable solvent. Ethylene glycol was selected as the potential solvent to extract the phenols from aromatic hydrocarbon, evaluated by area of two-phase region and the criterion of solvent power (SPi∞), selectivity (S∞) and performance index (PI). Liquid-liquid equilibria of the ethylene glycol + phenols + toluene ternary systems were measured in the temperature range (303.15–323.15) K under 101.3 kPa, and the results showed that ethylene glycol has a high extraction efficiency with distribution coefficient (between 2 and 12) and selectivity (between 7 and 255). Moreover, the NRTL and UNIQUAC models were successfully applied to correlate the experimental LLE data with RMSD less than 1.85%, indicating that both models can accurately describe LLE behaviour of this system. Thus, the corresponding binary interaction parameters would be helpful for separation process designing or optimizing.

Study of the LLE, VLE, and VLLE of the Ternary System Water + 1-Butanol + Isoamyl Alcohol at 101.3 kPa

The liquid–liquid equilibrium of the water + 1-butanol + isoamyl alcohol system at 303.15 and 313.15 K has been determined experimentally. The UNIQUAC, NRTL, and UNIFAC models have been employed to correlate and predict liquid–liquid equilibria (LLE) and compare them with the experimental data. Additionally, the vapor–liquid and vapor–liquid–liquid equilibria (VLE and VLLE, respectively) of this system have been determined using a modified Fischer LABODEST still. The data obtained have been used to correlate and obtain the binary interaction parameters for UNIQUAC and NRTL. The validity of the models to reproduce the VLE and VLLE data has been analyzed.

Experimental result and data correlation of liquid-liquid equilibrium for methyl isopropyl ketone + o, m, p-dihydroxybenzene + water at 333.15 K, 343.15 K and 353.15 K

In order to remove the dihydroxybenzene from coal chemical industry wastewater at high temperatures, the liquid-liquid equilibrium data of ternary system methyl isopropyl ketone (MIPK) + o, m, p-dihydroxybenzene + water was measured at 333.15 K, 343.15 K and 353.15 K under 101.3 kPa. The extraction effect of MIPK on dihydroxybenzene was evaluated by the distribution coefficient (D) and the separation factor (S). The Hand equation and the Bachman equation were used for verifying the consistency of the experimental data. Both regression coefficients were higher than 0.99, and it indicated that the experimental data had excellent reliability. Meanwhile, NRTL and UNIQUAC models were applied to correlate experimental liquid-liquid equilibrium data and then the binary interaction parameters were obtained. RMSD values of both models were similar and did not exceed 0.0050. Finally, comparing the extraction effect of MIPK between high and low temperatures, it was found that MIPK also can effectively extract the dihydroxybenzene from wastewater at high temperatures.

Evaluation of Gas Hydrate Formation Temperature for Gas/Water/Salt/Alcohol Systems: Utilization of Extended UNIQUAC Model and PC-SAFT Equation of State

Naturally occurring gas hydrates are of great importance as a strategic energy source. Hydrates affect coastal sediment stability, global climate change, and ocean carbon cycling. It is vital to understand the thermodynamic conditions of gas hydrates to control/manage and inhibit hydrate formation. A variety of equations of state (EOSs) have been utilized to model the thermodynamic behaviors of gas hydrates. In this study, the perturbed chain statistical association fluid theory (PC-SAFT) equation of state combined with van der Waals and Platteuw model is employed to determine the clathrate hydrate formation temperature of pure gases (e.g., methane, ethane, propane, isobutane, carbon dioxide, and hydrogen sulfide) and binary and ternary systems of hydrate gases. In addition, the gas hydrate formation conditions are investigated where methanol, ethanol, glycerol, NaCl, KCl, CaCl2, and MgCl2 as inhibitors are present. The UNIQUAC model is utilized in this work to obtain the hydrate formation conditions in s...

Prediction of Flash Temperature of Binary Mixtures Containing Alcohol–Alcohol and Alcohol–Acid Using a Combination of Activity Models and Group Contribution Methods

The present paper aims to examine the method used to calculate the flash temperature of binary mixtures containing alcohol–alcohol and alcohol–acid based on activity models of Wilson, UNIQUAC and NRTL. The binary interaction parameter is obtained by group contribution method in these equations. The advantage of this method is that the methods used to calculate the flash temperature are based on the activity coefficients and the binary interaction parameter are independent from VLE experiments and phase equilibria. These parameters may be obtained from group contribution methods for calculation of flash temperature of binary mixtures containing alcohol. Therefore, 12 binary mixtures containing 97 binary flash data were used; for the three models of Wilson, NRTL, and UNIQUAC, adjustable parameters were obtained by a similar method using group contribution method and it was later tested for three activity equations and 4 mixtures containing 33 binary flash data. Test results indicate that the overall average...

Determination and correlation of the solubility of L-arabinose and D-galactose in binary solvent mixtures from 278.15 to 333.15 K

L-arabinose and D-galactose could be released during the hydrolysis process of Arabic gum. The development of a crystallization process of L-arabinose is highly dependent on the knowledge of the solubility of both saccharides. In this work, the solubility of L-arabinose and D-galactose in binary mixtures of methanol-water or ethanol-water (mole fraction of water ≤0.5816) was determined at temperatures between 278.15 and 333.15 K by a static equilibrium method. The experimental data correlated well with the modified Apelblat equation, the simplified polynomial empirical equation, NRTL model and UNIQUAC model. Additionally, the thermodynamic properties including the dissolution enthalpy and entropy were obtained from the experimental data. Within the studied temperature range, the dissolution is endothermic and the dissolution process is non-spontaneous.

Vapor-liquid equilibrium in the binary and ternary systems containing ethyl propionate, ethanol and alkane at 101.3 kPa

The vapor-liquid equilibria at 101.3 kPa of seven binary systems: ethanol (1) + cyclohexane (2), ethanol (1) + n-hexane (2), ethanol (1) + n-octane (2), cyclohexane (1) + ethyl propionate (2), n-hexane (1) + ethyl propionate (2), n-octane (1) + ethyl propionate (2) and ethanol (1) + ethyl propionate (2), three ternary systems: ethanol (1) + cyclohexane (2) + ethyl propionate (3), ethanol (1) + n-hexane (2) + ethyl propionate (3) and ethanol (1) + n-octane (2) + ethyl propionate (3) at temperatures from 332.15 to 396.85 K were studied, all the binary VLE data passed the Herington test. Wilson, NRTL and UNIQUAC models were used to correlate experimental VLE data of the all systems to obtain interaction parameters through the MATLAB software and the experimental values were compared with the regression results. The Wilson and NRTL models reproduced the experimental values very well. Ternary VLE behavior were successfully predicted by the correlated binary parameters. The VLE data for the binary and ternary systems predicted by the correlated interaction parameters were in good agreement with all the experimental data.

Measurement and correlation of vapor–liquid equilibrium data for binary and ternary systems composed of (−)-β-caryophyllene, p-cymene and 3-carene at 101.33 kPa

Abstract New experimental vapor–liquid equilibrium (VLE) data for three binary systems composed of p-cymene + (−)-β-caryophyllene, 3-carene + (−)-β-caryophyllene, and 3-carene + p-cymene and for the ternary system of (−)-β-caryophyllene + p-cymene + 3-carene were obtained using a modified Ellis equilibrium still over the temperature range from 444.44 to 528.78 K at 101.33 kPa. The compositions of these mixtures were assessed using gas chromatography. The VLE data for the binary systems passed thermodynamic consistency tests based on the Herington method and Van Ness test. The thermodynamic consistency of the ternary system was checked by a Van Ness test. The VLE data for binary systems were correlated using the Wilson, NRTL, and UNIQUAC activity coefficient models with minor deviations. The ternary VLE data were also satisfactorily correlated using the Wilson, NRTL and UNIQUAC models. By comparing the experimental values for the ternary system with the values calculated using the three models, the average absolute deviation of the equilibrium temperature and vapor–phase composition were determined to be less than 0.57 K and 0.0060, respectively. These results indicated excellent agreement of the models with experimental values.

Salting-out Effect of Ionic Liquid, 1-Butyl-3-methyl Imidazolium Chloride on Aqueous d-Fructose or Sucrose Solutions at T = 298.15 K: Vapor–Liquid Equilibrium Study

Water activity and vapor pressure for aqueous {ionic liquid, 1-butyl-3-methyl imidazolium chloride + sucrose or d-fructose} solutions have been determined using the improved isopiestic method at T = 298.15 K. The reliability of local composition models of NRTL, NRF-NRTL, modified NRTL, Wilson, and UNIQUAC in the fitting the water activity values for the studied systems has been examined. For saccharides in aqueous and aqueous ionic liquid solutions and for ionic liquid in aqueous solutions, the unsymmetrical molal activity coefficients were computed. The interactions present in these systems were interpreted by the comparison of the molal activity coefficients of these saccharides in aqueous and aqueous ionic liquid solutions. Furthermore, salt effect of ionic liquid, 1-butyl-3-methyl imidazolium chloride has been compared with two previously studied ionic liquids 1-butyl-3-methyl imidazolium bromide and 1-hexyl-3-methyl imidazolium chloride. In this study, the effects of chain length and anion type of io...

Liquid-liquid equilibria of ternary and quaternary systems involving 5-hydroxymethylfurfural, water, organic solvents, and salts at 313.15 K and atmospheric pressure

HMF (5-hydroxymethylfurfural) is one of the bio renewable materials that can be used to produce a wide range of chemical products. In the HMF production process, yield and selectivity may be increased by liquid-liquid extraction of HMF using an organic solvent to prevent its degradation. Phase equilibrium data are required for rational design and optimal separation of HMF from the aqueous solution. In this study, liquid-liquid equilibrium (LLE) data of HMF, water, and methyl isobutyl ketone (MIBK) or 2-pentanol at 313.15 K (40 °C) and atmospheric pressure were measured and correlated using the NRTL and UNIQUAC models. The root mean square deviations (RMSD) of the NRTL and UNIQUAC models were 0.42% and 0.48% for the MIBK-HMF-water and 0.81% and 0.77% for the 2-pentanol-HMF-water system, respectively. The results indicated that higher distribution coefficients are achieved in the 2-pentanol-HMF-water system compared to the MIBK-HMF-water system. On the other hand, the separation ability of MIBK is better than that of 2-pentanol. In liquid-liquid extraction, not only a high distribution coefficient of HMF is important, but also a high separation factor is desirable to reduce the amount of co-extracted water. Therefore, in the present study the distribution coefficient of HMF from MIBK-HMF-water and the separation factor of the 2-pentanol-HMF-water system was improved by introducing a certain amount of salt into the aqueous solution. The salts examined in this study were based on the variety of cation (Na+, K+) and anion (Cl−, SO42−). The NRTL model was applied to correlate the LLE of organic solvent-HMF-water-salt systems, the results of which provided good agreement with the experimental data. The presence of salt can enhance the partitioning of HMF into the organic phase as well as the separation factor up to 2 times indicating the salting-out ability of the studied salts. The order of salting-out strength was NaCl > Na2SO4 > KCl > K2SO4 in which Cl− and Na+ demonstrated stronger salting-out ability than SO42− and K+.

Measurement and correlation of isobaric densities and viscosities for endo-dicyclopentadiene with hydrocarbons (C6–C8) at different temperatures

Accurate experimental isobaric densities and viscosities data between 288.15 and 318.15 K at 5 K intervals for five binary liquid mixtures of endo-dicyclopentadiene with 2,2-dimethylbutane, 3-methylpentane, n-hexane, n-heptane and 2,2,4-trimethylpentane are reported. Excess molar volume, $$V_{\text{m}}^{\text{E}}$$ , viscosity deviation, Δη, excess Gibbs energy of activation of viscous flow, G*E, have been calculated from these data and fitted by the Redlich–Kister-type equation. Prigogine–Flory–Patterson theory, Eyring–NRTL, Eyring–UNIQUAC, Eyring–Wilson, NRTL, UNIQUAC and Heil models have been applied to the binary systems.