Nonrandom Two-liquid Research Articles

Measurement of vapour-liquid equilibrium and e-NRTL model development of CO2 absorption in aqueous dipropylenetriamine.

Vapour-liquid equilibrium (VLE) of CO2 in aqueous dipropylenetriamine (DPTA) is investigated experimentally using a stirred equilibrium cell setup. Equilibrium solubility of CO2 is measured in the temperature and pressure range of (313-333) K and (1-100) kPa respectively. Composition of aqueous DPTA solvent used for the absorption study is in the range of (5-15) mass%. Experimental data shows higher CO2 loading capacity of this solvent compared to conventional solvents like monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), and N-methyldiethanolamine (MDEA) as well as recently developed polyamine solvents like aminoethylethanolamine (AEEA), piperazine (PZ), and hexamethylenediamine (HMDA). Experimental VLE data is then correlated using the electrolyte non-random two-liquid (e-NRTL) theory which is an activity coefficient-based model for the electrolyte system. Data regression system (DRS) in Aspen Plus® (V8.8) is employed to fit the e-NRTL model equation with the experimental data by regressing the model parameters. Model-predicted data is found to be in good agreement with the experimental VLE data with an average absolute deviation of 22.3%. Performance of aqueous DPTA solvent is also analysed by predicting solvent capacity, equilibrium liquid-phase speciation, and heat of CO2 absorption using the newly developed e-NRTL model for the investigated system.

An accurate water activity model for sulfuric acid solutions and its implementation on moisture sorption isotherm determination

Because of a lack of reliable models to predict the water activity (a w) of H2SO4 solutions, the standard sulfuric acid solution (SSL) method requires a periodic check and adjustment of the acid concentration to ensure that equilibrium will be reached at a predetermined a w point. To establish a reliable equation describing the a w of H2SO4 solutions, five molecular activity models, i.e. nonrandom two-liquid (NRTL), Wilson, universal quasi-chemical (UNIQUAC), modified NRTL-1 (M-NRTL 1) and modified NRTL-2 (M-NRTL 2), were introduced and compared in this study. Each of the models was applied to the 542 literature vapor-liquid equilibrium data points of H2SO4 solutions. The results showed that the NRTL model was the best with respect to its accuracy and simplicity. This NRTL model significantly simplified the implementation of the sulfuric acid solution method for MSI measurements. Excellent agreement was found between this simplified SSL method and the conventional saturated salt solution (SSS) method for MSI measurements of both microcrystalline cellulose (MCC) and apples at 25 °C. Therefore, this newly improved SSL method, based on the NRTL model, could be an inexpensive, convenient and reliable alternative to the conventional SSS method in food MSI measurements in the future. Highlights The NRTL model can accurately predict the a w of H2SO4 solutions. The NRTL model can significantly simplify the known sulfuric acid solution (SSL) method. This improved SSL method is valid and reliable for use in MCC and apples. A working table of the a w of H2SO4 solutions was developed for ease of use.

Thermodynamic Modeling of Aqueous LiCl, LiBr, LiI, and LiNO3 Solutions

Thermodynamic models are essential to facilitate the advancement of process design, optimization, and operation of electrolyte systems. In this work, a comprehensive thermodynamic framework based on the Electrolyte Nonrandom Two-Liquid model is developed to calculate phase equilibria behavior and salt solubility of aqueous LiCl, LiBr, LiI, and LiNO3 solutions. The model describes the non-ideality of the electrolyte solutions by using two binary interaction parameters for each molecule-electrolyte pair in the system. Each binary interaction parameter is further expressed with up to three temperature coefficients which are regressed from experimental data. To take into account the hydration of lithium ion, two separate chemistries for the dissociation of lithium salts are investigated. In the first case, the lithium ion is considered as a bare ion, Li+, while in the second case hydration of the lithium ion from Li+ to Li(H2O)+ is considered. The calculated thermodynamic properties compare adequately with the experimental data for both sets of chemistries for concentrations up to saturation and temperatures from 273.15 K up to 623.15 K. Moderate to significant improvements are observed with the incorporation of the hydration chemistry for aqueous LiCl, LiBr, and LiI solutions when compared to the non-hydrated lithium ion model results.

Experimental investigation and process simulation of biolubricant production from waste cooking oil

Waste cooking oil (WCO) or frying oil was used for synthesis of biolubricant via transesterification reaction. Biolubricant (dioleoyl ethylene glycol ester) was prepared from fatty acid methyl esters (FAMEs) of WCO with ethylene glycol (EG). The reaction was performed using calcium oxide (CaO) heterogeneous catalyst. Dioleoyl ethylene glycol ester is a potential biodegradable lubricant that could be used in industrial lubricant applications. The effect of changing operating conditions such as temperature, molar ratio of reactants, reaction time and catalyst loading was studied. The optimal conditions that achieved highest conversion were found to be 130 °C, 3.5: 1, 1.5 h and 1.2% (w/w) catalyst dosage. The produced biolubricant structure was tested using FTIR spectrum technique and its thermal stability was examined using TGA technique. The biolubricant properties were compared to two other biolubricants and also to specifications of four different ISO viscosity grade lubricants. It was found that produced biolubricant complies with ISO VG68 viscosity grade with better low temperature applicability. The process simulation was performed on Aspen HYSYS program version 9 using conversion reactor model and using Non-Random Two-Liquid (NRTL) activity coefficient model. Simulation results proved that the studied biolubricant production process is industrially applicable.

Performance of p-Toluenesulfonic Acid-Based Deep Eutectic Solvent in Denitrogenation: Computational Screening and Experimental Validation.

Deep eutectic solvents (DESs) are green solvents developed as an alternative to conventional organic solvents and ionic liquids to extract nitrogen compounds from fuel oil. DESs based on p-toluenesulfonic acid (PTSA) are a new solvent class still under investigation for extraction/separation. This study investigated a new DES formed from a combination of tetrabutylphosphonium bromide (TBPBr) and PTSA at a 1:1 molar ratio. Two sets of ternary liquid–liquid equilibrium experiments were performed with different feed concentrations of nitrogen compounds ranging up to 20 mol% in gasoline and diesel model fuel oils. More than 99% of quinoline was extracted from heptane and pentadecane using the DES, leaving the minutest amount of the contaminant. Selectivity was up to 11,000 for the heptane system and up to 24,000 for the pentadecane system at room temperature. The raffinate phase’s proton nuclear magnetic resonance (1H-NMR) spectroscopy and GC analysis identified a significantly small amount of quinoline. The selectivity toward quinoline was significantly high at low solute concentrations. The root-mean-square deviation between experimental data and the non-random two-liquid (NRTL) model was 1.12% and 0.31% with heptane and pentadecane, respectively. The results showed that the TBPBr/PTSADES is considerably efficient in eliminating nitrogen compounds from fuel oil.

Solubility of Sulfanilamide and Sulfacetamide in neat solvents: Measurements and interpretation using theoretical predictive models, first principle approach and artificial neural networks

Solubilities of Sulfanilamide and Sulfacetamide in neat solvents were both measured and collected from the literature. The set comprising 35 systems was interpreted in terms of the empirical and semi-empirical predictive models including Buchowski-Ksiazczak model (λh-equation), extended Buchowski's model (λβ-equation), modified Apelblat equation, van't Hoff-Yaws model, Non-Random Two Liquid (NRTL) model, Wilson model and the Weibull two-parameter extrapolation model. The advantage of corrected Akaike information criterion was used for precise quantification of the quality of each model. It turned out that the lowest values of this measure were found for the Buchowski-Ksiazczak approach indicating the best correlation with experimental solubility data. Interestingly, λβ-equation and van't Hoff–Yaws model give a fitting of almost the same quality but were slightly less accurate compared to λh-equation. The results of applied COSMO-RS computations suffered seriously from inaccuracies providing only a qualitative guess of solubility. Hence, machine learning procedure was applied for building a non-linear fully predictive model. The set of used molecular descriptors comes from COSMO-RS computations and characterizes intermolecular interactions in pure solvents. Based on the quality of obtained machine learning model it is possible to confirm that the selected set of descriptors can be used for solubility modeling and carries the most important information necessary for quantifying of saturated solutions.

Effect of Blending Ratio and Temperature on CO2 Solubility in Blended Aqueous Solution of Monoethanolamine and 2-Amino-2-methyl-propanol: Experimental and Modeling Study Using the Electrolyte Nonrandom Two-Liquid Model.

This paper reports the newly measured experimental data for CO2 solubility in a blended aqueous solution of monoethanolamine (MEA) and 2-amino-2-methyl-propanol (AMP) at different amine mixing ratios (MEA/AMP/H2O = 9:21:70, 15:15:70, and 21:9:70 wt %) and working temperatures (323.15, 373.15, and 383.15 K). The successive substitution method was used for calculating the mole fractions of all molecules (four molecules) and electrolytes (three cations and four anions) from the equilibrium along with the material and charge balance equations (11 equations). The electrolyte nonrandom two-liquid (e-NRTL) model was used to investigate nonideality in the liquid phase. Using the abovementioned thermodynamic models, the partial pressures of CO2 in the gas phase, mole fractions of all components in the liquid phase, pH variations, heats of absorption, and cyclic capacities of CO2 according to the absorption/desorption temperature and the blending ratio of MEA/AMP were estimated.

Liquid-liquid equilibrium for n-hexane + benzene + sulfolane, + 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]), + 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) and + the mixtures of [EMIM][NTf2] and [EMIM][EtSO4

The liquid-liquid equilibrium (LLE) data for three ternary mixtures of n-hexane + benzene + sulfolane, + 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) and + 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) and two quaternary ones of n-hexane + benzene + mixed ionic liquids respectively with fixed molar ratio 9:1 and 1:9 of [EMIM][NTf2] to [EMIM][EtSO4] were determined experimentally at (303.15, 313.15 and 323.15) K and atmospheric pressure. The experimental results showed that the ionic liquid of [EMIM][NTf2] captures higher molar distribution coefficient while one of [EMIM][EtSO4] is characterized with higher molar selectivity, compared to the sulfolane solvent that is extensively used for aromatic extraction in industry. The improvement of the composite separation performance for n-hexane and benzene was observed through mixing the above two ionic liquids. To represent the experimental diagram, the activity coefficient model of Non-Random Two-Liquid (NRTL) was employed to correlate the experimental data and good agreements between theoretical and experimental results were obtained. In general, the selected ionic liquid and its mixture in this work could be considered as a potential substitute for sulfolane.

Determination and modelling of density, viscosity and solubility of (R)-(-)-phenylephrine hydrochloride in methanol + ethyl acetate at (278.15–323.15) K and 0.1 MPa

For further optimizing the pipeline design of continuous crystallizer, in this research work, density, viscosity and solid-liquid equilibria (SLE) solubility of (R)-(-)-phenylephrine hydrochloride (R-PEC) in binary solvent of “methanol (MtOH) + ethyl acetate (EtAC)” were investigated at temperature T = (278.15–323.15) K under pressure p = 0.1 MPa. The results showed that experimental density and viscosity values were negatively related with temperature while the SLE solubility data had positive correlation with the experimental temperature. Moreover, density and viscosity profiles increased with the incremental molarity of R-PEC, similarly, solubility of R-PEC raised along with the mass fraction of MtOH in binary solvents. Hansen solubility parameter (HSP) was applied to investigate the solubility behavior of R-PEC in MtOH+EtAC, four selected solubility parameters could give a logical explanation on R-PEC solubility. By using Mathcad software (Version: 15), the Vogel-Tammann-Fulcher (VTF) equation was employed for the description of density as well as viscosity values. Values of average relative deviation (ARD), multi-correlation coefficient (R2) and root-mean square deviation (RMSD) between experimental data and predicted data showed that VTF equation could provide satisfactory correlations with the experimental data. Besides, solubility values of R-PEHC in selected binary solvent were correlated with three activity coefficient models including Wilson, NRTL (Non-Random Two Liquids) and UNIQUAC (Universal Quasi–Chemical) model by using Mathcad software, the UNIQUAC model were more suitable for correlation with experimental solubility than others in terms of ARD and RMSD. Furthermore, based on the experimental solubility results and regression parameters of UNIQUAC model, thermodynamic properties of mixing and dissolution process were discussed in this work, the results showed that the both processes of R-PEHC in MtOH+EtAC were always spontaneous and entropy driven, the mixing process and part of dissolution process (R-PEHC in MtOH + EtAC at T ≤ 303.15 K) were exothermic. Experimental densities, viscosities, solubility as well as selected models would be very helpful for optimizing the pipeline design (including material selection, size calculation and so on) of continuous crystallizer.

Synthesis and simulation of a distillation columns system for the propylene glycols mixtures separation

AbstractFour sequences were synthesized and simulated for the separation process of the propylene glycols mixtures: the direct, the indirect, and two proposed sequences. The simulation of the distillation columns system was performed with PRO/II program using a complete NRTL (nonrandom two‐liquids) thermodynamic model. Two mixtures were subject of the separation: one containing only propylene glycols, and another containing in addition a significant amount of water. The disadvantage of the direct and indirect sequences is that the columns are operated at high temperatures in the bottoms this fact leading to decomposition of propylene glycols. The proposed separation sequences aim to eliminate this disadvantage by taking into account the nearest effect of inert gas that water and propylene glycols with lower molar mass have on the separation mixture. The feed is introduced directly in the reboiler of the first column, where lower glycols and water act as an inert gas on the TePG vaporization. The proposed separation sequence of the propylene glycols and water mixture has a temperature in the reboiler with approximately 13 K lower beside the direct sequence.

Nonrandom two‐liquid activity coefficient model with association theory

AbstractConsidered one of the most versatile and widely used classical thermodynamic models to correlate phase equilibria behavior of nonideal systems, the nonrandom two‐liquid (NRTL) theory does not explicitly account for specific chemical associations such as hydrogen bonding. This deficiency has been recognized as the cause for unsatisfactory representation of association systems like methanol–alkanes binaries. This work presents a practical approach to integrate Wertheim's perturbation theory for association contribution with the classical NRTL model. Specifically, the association contribution is calculated from pre‐determined molecule‐specific association strengths while the physical interaction contribution is captured with NRTL binary interaction parameters. The resulting association NRTL model correlates fluid phase equilibria of association systems with few adjustable parameters and offers improved predictive capability for higher order systems.

Mobile ion partitioning in ion exchange membranes immersed in saline solutions

Ion exchange membranes (IEMs) are extensively used in separation and energy storage systems. Prior studies have suggested that rigorous thermodynamic modeling is essential to describe mobile ion partitioning in IEMs, especially weakly charged ionic membranes, immersed in aqueous salt solutions. Based on a recently developed polyelectrolyte nonrandom two-liquid (NRTL) activity coefficient model, this work presents a thermodynamic analysis for the mobile ion partitioning between external salt solutions with ionic strength from 0.01 to 1 molal and membranes of poly (ethylene glycol diacrylate) (PEGDA) copolymerized with 2-acrylamido-2-methylpropanesulfonic acid (AMPS). We show that mobile ion partitioning in the uncharged membranes and the weakly charged membranes immersed in saline solutions is controlled by the long-range “point-to-point” electrostatic interactions and the short-range van der Waals interactions in the membrane phase. For the strongly charged membrane samples, the long-range “point-to-line” electrostatic interactions also play a role, the mobile ion mean ionic activity coefficients are close to unity, and the ion sorption data may be qualitatively interpreted with either the ideal Donnan equilibrium model or Manning's limiting law.

Isothermal Vapour-Liquid Equilibrium Measurements for the butan-1-ol + butane-1,4-diol/butane-2,3-diol system within 353.2–388.2 K

In this study, the isothermal binary vapour-liquid equilibrium (VLE) data for the butan-1-ol + butane-1,4-diol/butane-2,3-diol system was measured and modelled, for use in the design and rating of separation processes. P-T-x-y equilibrium measurements were performed at four temperatures from approximately 353–388 K. A dynamic-analytical apparatus was utilized to perform the measurements at sub-atmospheric conditions. The measured data was modelled by employing the γ-Φ approach. The liquid-phase correction was accounted for using the Non-Random Two-Liquid and Universal Quasi-Chemical activity coefficient models while the Hayden and O'Connell correlation for the virial equation of state was used to account for the vapour-phase correction. Thermodynamic consistency tests were performed using the point and area tests for the measured experimental data and the data sets passed both tests.

Study of the capability of 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid as solvent in the separation of water from 1-propanol or 2-propanol at different temperatures

After the good behavior of different 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) used as solvents in the separation of 1-propanol and 2-propanol from water, liquid-liquid equilibria data was measured from a system formed by a ternary mixture of water, 1-propanol or 2-propanol and 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([dmim][Tf2N]) at 283.2, 303.2 and 323.2 K and atmospheric pressure. The non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models were employed to obtain the thermodynamic parameters of both ternary mixtures, with good results in all cases. Finally, the capability of [dmim][Tf2N] to separate both azeotropic mixtures was studied through the distribution coefficient and selectivity and compared with the results obtained using different 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ILs.

Measurement and correlation of coumarin solubility in aqueous solution of acidic deep eutectic solvents based on choline chloride

The solubility of coumarin in three aqueous solutions of acidic deep eutectic solvents (DESs) based on choline chloride (ChCl) as hydrogen bond acceptor (HBA) with some carboxilic acids (propionic acid, lactic acid and acetic acid) as hydrogen bond donors (HBD) have been measured using the shake flask method at T = (298.15 to 313.15) K. According to obtained results, the solubility of coumarin increases with increasing the weight fraction of ChCl/propionic acid more than 100-fold. The experimental solubility data were correlated by electrolyte Nonrandom Two-Liquid (e-NRTL),Wilson and UNIQUAC activity coefficient models. Then, the dissolution thermodynamic properties, enthalpy, Gibbs free energy and entropy were calculated based on Gibbs and van't Hoff equations to investigate the solvation behavior of coumarin in the aqueous DES solutions.

Isobaric vapor – liquid – liquid equilibrium for water + MTBE + alcohol (ethanol or 1-butanol) mixtures

Vapor – liquid – liquid equilibrium (VLLE) for water + MTBE + ethanol and water + MTBE + 1-butanol ternary systems have been measured in a modified dynamic Guillespie type cell at the isobaric condition of 101.3 kPa and over the temperature range from 325.6 to 328.9 K for water + MTBE + ethanol mixture and from 329.5 to 355.1 K for water + MTBE + 1-butanol mixture. The quality of the measured data is thermodynamically validated by the L/W Wisniak's consistency point- point test. According to the experimental results, the liquid – liquid equilibria are Type I for water + MTBE + ethanol mixture and Type II for water + MTBE + 1-butanol mixture. The VLLE for water + MTBE + ethanol mixture displays heterogeneous ternary azeotrope whereas the water + MTBE + 1-butanol mixture is a zeotropic ternary mixture. The experimental VLLE data for both ternary mixtures are correlated by a modified version of the nonrandom two-liquids (NRTL) activity coefficients model, which incorporates a ternary contribution. This ternary contribution reduces the global average absolute deviation from 5 % to 1.3 % for water + MTBE + ethanol mixture and from 3.1% to 1.9 % for water + MTBE + 1-butanol mixture.The experimental isobaric VLLE data of the ternary mixtures are also accurately modeled by applying the Peng–Robinson Stryjek–Vera equation of state appropriately extended to mixtures employing the modified Huron–Vidal mixing rule with the NRTL activity coefficient model. This model allows directly transferring the experimental excess Gibbs energy function to the EoS model for equilibrium calculation purposes. This theoretical framework shows that experimental VLLE data can be accurately predicted and provide a route to interpolate values of the phase equilibrium.

Promising Thiolanium Ionic Liquid for Extraction of Aromatics from Aliphatics: Experiments and Modeling

Four ionic liquids (ILs) consisting of the bis(trifluoromethylsulfonyl)imide anion paired with a phosphonium, pyridinium, imidazolium, or thiolanium cation were investigated as potential solvents to separate aromatic from aliphatic compounds in a liquid–liquid extraction process. The thiolanium IL was chosen due to its structural similarity to sulfolane, which is the most widely used organic solvent for aromatic/aliphatic separation in the industry. Interestingly, ternary liquid–liquid equilibrium data shows that 1-n-butylthiolanium bis(trifluoromethylsulfonyl)imide performs as well as the equivalent imidazolium IL despite the fact that it is not aromatic and cannot use π–π interactions (which are available to imidazolium ILs) to enhance aromatic solubility and selectivity. Moreover, we provide quantification of the IL solubility in the organic-rich phase, which is on the order of 10–4 mole fraction. This quantity is important because it would represent IL loss and product contamination in a real extraction process; however, it is commonly reported to be nondetectable. The nonrandom two-liquid (NRTL), perturbed-chain statistical associating fluid theory (PC-SAFT), COSMO-RS, and COSMO-SAC models are appropriate for the mixtures explored, and each model’s strengths and weaknesses are discussed.

Ternary liquid\u2013liquid equilibrium data for n-Hexane-Benzene-DES (choline chloride/ethylene glycol, choline chloride/glycerol, choline chloride/urea) at 303\xa0K and 101.3\xa0kPa

In this study, deep eutectic solvents (DESs) were prepared using choline chloride as hydrogen bond acceptor (HBA) and ethylene glycol (EG) or glycerol (GLY) or urea (U) as hydrogen bond donor (HBD) and were evaluated as solvents in the extraction of benzene from n-hexane. Six of such solvents were prepared using different molar ratios of HBA: HBD and code named DES1, DES2, DES3, DES4, DES5 and DES6. Liquid–liquid equilibria (LLE) data for the ternary systems of n-hexane-benzene-DESs were measured at 303 K and 101.3 kPa. Solubility data and mutual solubilities between n-hexane and DES were measured using the traditional cloud point method. The tie lines were obtained using titration and refractive index measurements on both phases (n-hexane phase and DES-phases). The ternary systems exhibit type-1 phase behavior. The Othmer-Tobias and Hands equations were applied to examine the reliability of the LLE data. The tie-line data were correlated using the nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) thermodynamic models, and their corresponding binary interaction parameters were determined. The results show that the maximum separation factors were 31.24, 462.00, 15.24, 37.83, 174.60 and 126.00 for DES1, DES2, DES3, DES4, DES5 and DES6, respectively. The glycerol based DES (DES2 and DES5) show the highest separation factors and thus considered the most suitable for separating benzene from hexane. The regression coefficient for both Othmer-Tobias and Hand equations are higher than 0.99 for all DESs, indicating the reliability and consistency of the data. Both NRTL and UNIQUAC models adequately capture the experimental data.

Prediction of thermodynamic properties of organic mixtures: Combining molecular simulations with classical thermodynamics

The binary interaction parameters of the nonrandom two liquid (NRTL) thermodynamic model are predicted for several organic mixtures using molecular simulations. Based on the theoretical framework of the two-fluid theory, the binary interaction parameters are expressed in terms of the interaction energies, size of the molecules, and size of the local molecular domains; these quantities are calculated from molecular simulations. We show that our technique is robust in terms of its predictions involving organic mixtures with compatible chemical characteristics while we propose possible modifications in the case of mixtures involving incompatible chemical components or significant size disparity, where there is a notable difference between the interaction parameters calculated from simulations and those obtained from experimental data regression. We further demonstrate that the binary interaction parameters calculated from data regression are not unique and that molecular simulations can guide the parameter selection process by identifying physically relevant binary interaction parameters. Requiring only the local molecular structure information from molecular simulations, the method offers fast and reliable prediction of phase equilibrium properties, especially in cases where limited experimental data are available.

Influence of Temperature on Liquid–Liquid Equilibrium of Methanol + Aromatic + Isooctane Ternary Systems

The influence of temperature on the miscibility of the {methanol + p-xylene + isooctane} and {methanol + benzene + isooctane} ternary systems at atmospheric pressure are investigated. The effect of temperature on the phase equilibrium is discussed for each system. All chemicals are verified using gas chromatograph, density, viscosity and refractive index. Phase equilibrium are reached using a modified version of measurement equipment used previously. Some ternary systems and binary subsystems are taken from the literature at different temperatures to determine the influence of the temperature on the systems. The upper critical solution temperature for the methanol + isooctane binary system was determined by the constant-composition method with an accuracy of ± 0.1 K. Experimental data are compared with the literature. Calculated values by the non-random two liquids (NRTL) and universal quasi-chemical (UNIQUAC) equations are contrasted with experimental data for the ternary systems. Deviations from the experimental binodal curve have good adjustment of less than one per cent for all systems.