Liquid Equilibrium Data Research Articles

Phase behavior of carbon dioxide + 2,4-dimethylpentane binary system at high pressures

The phase behavior of the branched alkane 2,4-dimethyl pentane (2,4-DMP) and carbon dioxide (CO2) binary mixture that has no published data, to the best of our knowledge, was studied. The liquid–vapor critical line was determined up to 121.4 bar and 422.35 K, as well as vapor–liquid equilibrium (VLE) data at different constant temperatures (323.15, 343.15, 363.15, and 383.15) K and pressures between (10.4 and 120.4) bar. Phase behavior investigation was carried out in a high-pressures (HP) cell fitted with a pair of sapphire windows, one acting as a piston, hence volume up to 60 cm3, utilizing a static-analytical approach with phases sampling by the so called ROLSI valves (rapid online sample injectors) connected to a gas chromatograph (GC) for composition determination. The isothermal and critical data points for the carbon dioxide + 2,4-dimethylpentane binary mixture were modeled with the cubic equations of state (EoSs), i.e., Soave–Redlich–Kwong (SRK), Peng–Robinson (PR), and General Equation of State (GEOS), in combination with van der Waals mixing rules (one- and two-parameter conventional mixing rules, 1PCMR and 2PCMR). The calculations demonstrated that the selected models are capable of correctly reproducing the phase behavior of the mixture under study.

A comprehensive method of ionic liquid screening and experimental verification for simultaneous separation of multiple sulfides from oil

Ionic liquid (IL) as the extractant has shown an excellent performance in oil desulfurization. However, it is still a great challenge to select an appropriate IL that can simultaneously remove multiple sulfides from oils due to enormous ILs' quantities. In this work, an ILs' screening method based on the fuzzy comprehensive evaluation function and COSMO-RS method was developed for oil extraction desulfurization. Four typical aromatic thiophene sulfides – thiophene (TS), benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) were considered as the removal targets, and n-heptane was chosen as the model oil. By this method, a single IL – 1-butyl-3-methylpyridinium dicyanamide ([BMPy][DCA]) was selected from 702 ILs for removing the four sulfides from n-heptane. Liquid-liquid equilibrium (LLE) data of n-heptane + TS/BT/DBT/4,6-DMDBT + [BMPy][DCA] systems at 298.15 K were measured and then correlated by the NRTL equation. A data processing method for LLE experimental indices, distribution coefficient and selectivity, was proposed for their crossed curves and different measuring ranges to facilitate the comparison of ILs' extraction performance. The comprehensive experimental indices based on this processing method were compared with the comprehensive predicted indices obtained by screening. The results showed a consistent trend between the two, and the excellent desulfurization performance of [BMPy][DCA] was confirmed. The separation mechanism was then analyzed through the quantum chemistry method. The results showed that the interactions of four sulfides with either n-heptane or [BMPy][DCA] both were the van der Waals interaction and steric effect. The [BMPy][DCA] could attract the sulfides more potently than the n-heptane, demonstrating the extraction's mechanism and characteristics. The stronger itself interactions of BT, DBT and 4,6-DMDBT as solid sulfides limited their solubility in liquid–liquid two phases. In addition, the decomposition of interaction energy showed that the attraction between the sulfides and the [BMPy][DCA] was dominated by dispersion, assisted by electrostatics, and equipped with a small amount of induction. The essence of repulsion between them was the exchange-repulsion.

Measurement of vapor-liquid equilibrium for the binary system propene (R1270) + trans-1,3,3,3‑tetrafluoropropene (R1234ze(E)) at temperatures from 288.18 K to 318.18 K

The search for alternative refrigerants that are environmentally friendly and highly efficient has become one of the most urgent and important issues facing the refrigeration industry. R1270 has excellent thermodynamic properties, but its high flammability limits its range of applications. R1234ze(E) is an environmentally friendly refrigerant with negligible flammability though it has the drawback of poor heat transfer performance. R1270 can be blended with R1234ze(E) as a new mixture refrigerant. vapor–liquid equilibrium (VLE) is the basic physical property of mixtures. The vapor–liquid equilibrium data have been measured for the binary system R1270/ R1234ze(E) based on the liquid-phase cycling method at four temperatures (288.15 K, 298.15 K, 308.15 K, 318.15 K). All the experimental data were regressed by the Peng-Robinson (PR) equation of state (EoS) with the Huron–Vidal (HV) mixing rule involving the non-random two-liquid (NTRL) activity coefficient model, and the PR EoS relating to the van der Waals (vdWs) mixing rule. The results show that the predicted values by the two models are in good agreement with the experimental data, and the prediction accuracy of the PR + HV + NTRL model was higher than that of the PR + vdWs model. In addition, azeotropic behaviors of the binary mixture have been found in the measured temperature range.

Liquid–Liquid Equilibrium Measurement for the Separation of n-Propanol + n-Propyl Acetate Using Imidazolium-Based Ionic Liquids with Different Anions at T = 303.15 K

Separating the mixture of the target product n-propyl acetate (NPAC) and the unreacted reactant n-propanol (NPA) is necessary during the production of NPAC. NPA and NPAC cannot be separated by simple distillation because the two could form an azeotrope under atmospheric pressure. Liquid–liquid extraction is an energy-saving and environment-friendly method for separating azeotropic mixtures. Ionic liquids (ILs) are promising alternatives to conventional extractants for separating azeotropes due to the advantages of designability and negligible vapor pressure. In this study, the liquid–liquid equilibrium (LLE) data for the ternary systems of NPAC + NPA + 1-butyl-3-methylimidazolium dihydrogen phosphate ([BMIM][H2PO4]) or 1-butyl-3-methylimidazolium thiocyanate ([BMIM][SCN]) or 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) were determined at 303.15 K and 101.3 kPa. The accuracy of the experimental LLE data was checked by the Bachman, Hand, and Othmer–Tobias equations. The selectivity and partition coefficient were calculated to evaluate the extraction capability of the selected extractants. The experimental LLE data were correlated with the nonrandom two-liquid model, and the binary interaction parameters were regressed. Finally, the separation mechanism of the three ILs was explored through σ-profile analysis.

Measurement and Correlation of Isobaric Vapor–Liquid Equilibrium Data for n-Hexane, Methylcyclopentane and N,N-Dimethylamide Systems at 101.3 kPa

Measurement and Correlation of Isobaric Vapor–Liquid Equilibrium Data for n-Hexane, Methylcyclopentane and N,N-Dimethylamide Systems at 101.3 kPa

Pyridine Ionic Liquid-Based Deep Eutectic Solvents Selectively Separating Toluene from Alkanes

Naphtha is an important raw material for ethylene cracking, and the aromatics in it can affect the ethylene yield due to the easy coking during the cracking process. Therefore, it is important to separate the aromatics from naphtha to increase the alkane content and improve the ethylene cracking production. Liquid–liquid extraction separation of the aromatic/alkane mixture is one of the effective pathways, and the key is the design and synthesis of new efficient extractants. In this work, a novel pyridine ionic liquid-based deep eutectic solvent (DES) for the separation of aromatics from alkanes was proposed and successfully synthesized. 1-Ethylpyridinium chloride (EpyCl) was used as the hydrogen bond acceptor and levulinic acid (LA) as the hydrogen bond donor. Among them, the π–π interactions between pyridine ring, C═O, and aromatic ring can enhance the interactions with aromatic compounds. In contrast, the introduction of acidic groups can increase the polarity of DES, enhance the induced polarization of unsaturated bonds in aromatic rings by DES, and thus increase the non-bonding force with aromatics. Toluene/n-heptane and toluene/cyclohexane were used as simulated oil systems. The optimal ratio of EpyCl/LA is 2:1, which has the best extraction efficiency, stability, and reusability; the selectivity of toluene was up to 69.57 for the toluene-n-heptane system, while it was 24.41 for the toluene-cyclohexane system. The reliability of the liquid–liquid equilibrium data was verified by using the Othmer–Tobias correlation equations, and the basic system physical property data were obtained by fitting with the NRTL thermodynamic model. The interaction mechanism between DES and toluene/alkanes was revealed by AIM topology analysis, IGMH analysis, and symmetry-adapted perturbation theory energy decomposition. The interaction between DES and toluene/alkanes is a van der Waals force, dominated by dispersion forces.

Population Balance Modeling of Diastereomeric Salt Resolution

Diastereomeric salt crystallization is a classical, widely applicable chiral resolution technique, which enables the separation of the enantiomers of both racemate and conglomerate-forming compounds. A resolution method for racemic pregabalin with l-tartaric acid was developed to obtain pure (S)-pregabalin l-tartrate monohydrate crystals with the yield ranging from 43 to 50%. A series of designed resolution experiments were executed at different cooling rates and temperature end points to estimate the crystallization kinetics using population balance modeling. Inline ATR-FTIR measurements of these experiments were used to calculate concentrations in the crystallization phase and to collect solid–liquid equilibrium data by the solubility trace method after product sampling. Since diastereomeric salts are dissociable ionic compounds, solubility product expressions were used in the model to express the relative supersaturation as the driving force of crystallization. As a result, a population balance model with secondary nucleation, growth, and agglomeration mechanisms was identified, and the simulated supersaturation profiles and product size distributions well reproduced the measured data.

Research on separation sulfides from fuel oil using sulfolane: Liquid-liquid equilibrium and mechanism exploration

Separation of sulfides from fuel oil is of great significance for environmental protection. In this paper, the organic solvent (sulfolane) was selected to separate sulfides (thiophene and 2-methylthiophene) from model fuel oil (n-heptane). The liquid–liquid equilibrium data of the mixtures (n-heptane + thiophene/2-methylthiophene + sulfolane) were measured at 303.15, 313.15 and 323.15 K under 101.3 kPa. The mass conservation of the experimental data were checked, and the reliability of the tie-lie data were evaluated by the Bachman, Hand and Othmer-Tobias equations. The extraction performance of sulfolane was assessed through the separation factor and partition coefficient, and compared with those for other reported solvents, indicating that sulfolane has better extraction performance for thiophene compared with 2-methylthiophene. Then, the quantum chemical calculation was applied to found the separation mechanism of sulfolane. The analysis of electrostatic potential, interaction energies, and reduced density gradient showed that the main interactions between sulfolane and thiophene (or 2-methylthiophene) were van der Waals and weak hydrogen bond forces. Finally, the non-random two-liquid theory (NRTL) and universal quasi-chemical theory (UNIQUAC) models were applied to fit the tie-line data of the investigated mixtures with the root-mean-square deviation (RMSD) lower than 0.01. The mixed surface analysis method based on Gibbs energy topology is used to verify the binary interaction parameters, which provides basic data for simulating the separation process of sulfide in fuel oil.

Liquid-liquid equilibria of the ternary systems water + C1 – C3 alcohols + dimethyl adipate at 298.15 K and atmospheric pressure: Experimental data and modeling

The aim of this study was to examine the possibility of using a green organic solvent, dimethyl adipate (DMA), as a separation agent in the extraction of different alcohols from aqueous solutions. For that purpose, the liquid–liquid equilibria (LLE) of four ternary systems were analytically determined at 298.15 K and atmospheric pressure using stirred and thermo-regulated cells: {water + methanol + dimethyl adipate (DMA)}, {water + ethanol + DMA}, {water + 1-propanol + DMA}, {water + 2-propanol + DMA}. Phase diagrams for these four ternary systems were obtained by determining a binodal curve and tie-lines data using a visual cloud-point method, but also gas chromatography. Distribution coefficients and separation factors were calculated for the immiscibility region. Hand and Othmer-Tobias correlations were used to examine the reliability of the tie-line data. In addition, the experimental ternary LLE data were correlated with the UNIversal QUAsiChemical (UNIQUAC) activity coefficient models. The obtained results showed that DMA is a suitable candidate for the extraction of methanol, ethanol, 1-propanol, and 2-propanol from water. With some alcohols, this potential is more noticeable than with others. The potential of DMA as a separation agent is increasing in the following sequence: methanol < ethanol < 2-propanol < 1-propanol, and that also could be noticed from the selectivity values that also increase in this sequence. The UNIQUAC model proved as successful in correlating the LLE data.

Measurement and Correlation of Isothermal Vapor–Liquid Equilibrium Data for (−)-α-Pinene + (−)-β-Pinene + Water + Phenoxyacetic Acid

Isothermal vapor–liquid equilibrium data of the binary system (−)-α-pinene + (−)-β-pinene and the quaternary system (−)-α-pinene + (−)-β-pinene + water + phenoxyacetic acid were measured at 313.2, 323.2, and 333.2 K using headspace gas chromatography. The experimental data showed that the addition of phenoxyacetic acid and water promoted the separation of (−)-α-pinene and (−)-β-pinene. The experimental data were correlated using the UNIQUAC and NRTL models. The two models showed good correlation for the binary system, whereas the UNIQUAC model gave more accuracy for the quaternary system. Moreover, the COSMO-RS model can be an efficacious method for predicting VLE data of the determined binary and quaternary systems. In addition, the optimal spatial configuration and binding energy between the molecules were obtained by DFT, and the effects on (−)-α-pinene and (−)-β-pinene with the addition of phenoxyacetic acid and water were discussed on the molecular scale.

Performance of Organic Salts as Salting-Out Media on Recovering Nicotine from Water

Three degradable organic salts, sodium formate (NaCHO2), sodium succinate (Na2C4H4O4), and sodium citrate (Na3C6H5O7), were evaluated for the extraction of nicotine from aqueous solutions by forming two-phase systems. The detailed phase diagrams, including the binodal curves and tie-lines, were experimentally determined at 298.15 K and atmospheric pressure by the cloud point method. The three empirical equations including Merchuk, Pirdashti, and Hu models gave a perfect correlation of the experimental binodal data, and the reliability of liquid–liquid equilibrium data was evaluated using the Othmer–Tobias and Bancroft equations. It could be found that all adopted organic salts promoted the expansion of two-phase regions and had a high partition yield for nicotine extraction from water. The relative tendency of the anions to form aqueous two-phase systems being C6H5O73– > C4H4O42– > CHO2– was consistent with their valence order, which could be explained by the Gibbs hydration free-energy theory. Furthermore, the salting-out ability of salt anions was also in accordance with the parameter order (Na3C6H5O7 > Na2C4H4O4 > NaCHO2) of the calculated effective excluded volume. Increasing the temperature from 298.15 to 318.15 K and the pH value from 8.0 to 11.0 at 298.15 K was conducive to the two-phase formation of the ternary nicotine + Na3C6H5O7 + water system to increase the distribution coefficients and recovery percentages of nicotine. Computational thermodynamics of cloud point indicated that the more negative Gibbs free energy with temperature promoted the desolvation of nicotine to migrate preferentially to the top phase. It was concluded that degradable organic salts would be effective for nicotine extraction at an industrial scale.

Determination and Correlation of Vapor–Liquid Equilibria for the Nitric Acid + Water, Nitric Acid + Water + Phosphoric Acid, and Nitric Acid + Water + Phosphoric Acid + Sulfuric Acid System

The wet-process production of phosphoric acid by the nitric acid method is considered as a promising technology with great development prospects due to no production of the byproduct phosphogypsum. However, the traditional nitro-phosphate fertilizer producing process cannot separate nitrogen and phosphorus thoroughly, which limits its applications. The key to solving this problem is to remove nitric acid from the crude phosphoric acid product obtained in the nitric acid wet process by evaporation. Therefore, it is important to measure the vapor–liquid equilibrium (VLE) data of the nitric acid + water + phosphoric acid + sulfuric acid quaternary system under different pressures and concentrations. In this study, the VLE data of the following systems were measured at 10, 20, 40, 60, 80, and 97.4 kPa by the quasi-static ebulliometric method: (1) nitric acid + water; (2) nitric acid + water + phosphoric acid; and (3) nitric acid + water + phosphoric acid + sulfuric acid. The electrolyte non-random two-liquid parameters for the following pairs were correlated with the VLE data by using Aspen Plus as a tool: HNO3-H2O, H3PO4-H2O, HNO3-H3PO4, HNO3-H2SO4, H3PO4-H2SO4, H+[H2PO4]−-H+[NO3]−, H+[NO3]−-H+[HSO4]−, and H+[H2PO4]−-H+[HSO4]−. The obtained VLE data and interaction parameters can provide the basis for the nitric acid method of mother liquor denitrification in the subsequent industry.

Isobaric Vapor–Liquid Equilibrium of the Binary Mixtures Toluene + Styrene and Styrene + α-Methylstyrene

Isobaric vapor–liquid equilibria of the binary mixtures toluene + styrene at 30 and 40 kPa and styrene + α-methylstyrene at 20 and 25 kPa were measured applying a recirculation still. The measured vapor–liquid equilibrium data were modeled adopting the non-random two-liquid (NRTL) excess Gibbs energy model with the RK (Redlich–Kwong) equation of state. The NRTL binary interaction parameter optimization was carried out employing own measured data and literature data for the toluene + styrene system. The applied model correlates well with the experimental data at the pressure range of 101–30 kPa. Moreover, the NRTL binary parameter regression was performed applying own measured data and literature data separately for the styrene + α-methylstyrene system. The model fitted with the parameters obtained from own measured data described the multiphase behavior of the system better than the parameters obtained from literature data. Additionally, the binary systems showed ideal behavior over the whole range of investigation as the calculated activity coefficients approached unity and no azeotropes were observed.

Absorption of ethylene dichloride with imidazolium-based ionic liquids

A series of imidazolium-based ionic liquids (ILs) with good thermal stability, consisting of [Bmim][BF4], [Bmim][OAc], [Bmim][SCN], [Bmim][DCA], [Emim][DCA], and [Hmim][DCA], were synthesized as absorbents for the absorption of ethylene dichloride (EDC). Among them, the ILs with the anion of [DCA]- possess the best absorption performance of EDC, and [Bmim][DCA] has the EDC absorption capacity of 0.3700 g EDC/g IL (313.15 K, atmospheric pressure) for the given inlet EDC concentration, higher than that of the other Bmim-based ILs. It was demonstrated that the absorption of EDC by [Bmim][DCA] is physical absorption, and the chemical structures of [Bmim][DCA] were consistent after five absorption–desorption cycles as well as no obvious decay in absorption capacity. It was demonstrated that anions of ILs play a more significant role in EDC absorption compared with cations through the analysis of interaction energy and weak interaction obtained by quantum chemical calculation, which also confirms the anions and cations act synergistically on EDC by H-bond and van der Waals (vdW) interaction. Besides, the vapor–liquid equilibrium (VLE) data for [Bmim][DCA]-EDC binary system with different compositions were determined at 303.15–353.15 K and compared with the predicted vapor pressure by the UNIFAC-Lei model. The predicted results show a good agreement with the experimental data, with an average relative deviation (ARD) of 3.98 %, indicating the reliability of the UNIFAC-Lei model.

Isobaric Vapor–Liquid Equilibrium Experiment of N-Propanol and N-Propyl Acetate at 101.3 kPa

N-Propanol (NPA) and n-propyl acetate (NPAC) can form an azeotrope under normal pressure, so their separation cannot be carried out by conventional distillation. Therefore, 1-butyl-3-methylimidazole acetate ([BMIM][OAC]) and ethylene glycol (EG) were selected as entrainers for extractive distillation of the two substances. Isobaric vapor–liquid equilibrium data were obtained by experiments of NPA + NPAC, NPA + NPAC + [BMIM][OAC], and NPA + NPAC + EG at normal pressure; the experimental results showed that the separation effect of [BMIM][OAC] is significantly better than that of EG. Finally, the data were fitted and correlated with the NRTL model. The ARD (average relative deviation) of NPA + NPAC, NPA + NPAC + [BMIM][OAC], and NPA + NPAC + EG is less than 5%, indicating that the NRTL model has good applicability to the vapor–liquid system.

Isobaric Vapor-Liquid Equilibrium Data for Tetrahydrofuran + Acetic Acid and Tetrahydrofuran + Trichloroethylene Mixtures.

Vapor-liquid equilibrium (VLE) data for the binary systems tetrahydrofuran (THF) + acetic acid (AA) and THF + trichloroethylene (TCE) were measured under isobaric conditions using an ebulliometer. The boiling temperatures for the systems (THF + AA/THF + TCE) are reported for 13/15 compositions and five/six different pressures ranging from 50.2/60.0 to 101.1/101.3 kPa, respectively. The THF + AA system shows simple phase behavior with no azeotrope formation. The THF + TCE system does not exhibit azeotrope formation but seems to have a pinch point close to the pure end of TCE. The nonrandom two-liquid (NRTL) and universal quasichemical (UNIQUAC) activity coefficient models were used to accurately fit the binary (PTx) data. Both models were able to fit the binary VLE data satisfactorily. However, the NRTL model was found to be slightly better than UNIQUAC model in fitting the VLE data for both systems. The results can be used for designing liquid-liquid extraction and distillation processes involving mixtures of THF, AA, and TCE.

Isobaric Vapor–Liquid Equilibria of Binary Systems Containing Oxygenated Biofuel Compounds (Ethanol + Cyclopentanone, Propyl Butanoate + 4-Methylphenol, Cyclopentanone + Propane-1,2-diol) at Atmospheric Pressure

The isobaric phase equilibrium data for the binary systems of ethanol + cyclopentanone, propyl butanoate + 4-methylphenol, and cyclopentanone + propane-1,2-diol at atmospheric pressure were measured using a modified distillation apparatus. The Herington and Van Ness tests were employed to confirm the thermodynamic consistency of the experimental data. In addition, the Wilson, NRTL, and UNIQUAC models were used to correlate experimental vapor–liquid equilibrium data. The corresponding binary interaction parameters (BIPs) for the three models, which are useful for the modeling and designing separation processes involving biofuel, were obtained using a maximum likelihood objective function. It has been confirmed that when appropriate BIPs are used in each model, the outputs are consistent with each other and with experimental data.

Separation of ethylene glycol, 1,2‐butanediol and 1,2‐propanediol with azeotropic distillation

Abstract1,2‐butanediol (1,2‐BDO) and 1,2‐propanediol (1,2‐PDO) are inevitably side produced in the ethylene glycol (EG) production processes from non‐petroleum routes, but are very difficult to separate by the ordinary distillation method because of the closeness of their boiling temperatures to EG, thus compromise the economy of these processes. The azeotropic distillation process using 1‐octanol (CPO) as an entrainer to separate EG and 1,2‐BDO mixture with or without 1,2‐PDO was studied in this paper. Four binary vapour–liquid equilibrium data of EG‐1,2‐BDO, EG‐CPO, 1,2‐BDO‐CPO, and 1,2‐PDO‐CPO were measured using an Ellis equilibrium kettle and regressed with the thermodynamic model of non‐random two liquid to obtain the corresponding binary interaction parameters. On this basis, azeotropic distillations with CPO as an entrainer were designed to separate EG and 1,2‐BDO with or without 1,2‐PDO. The complete separation processes, including the azeotropic distillation and CPO recovery process consisting of extraction with H2O and subsequent distillation, were simulated and optimized with Aspen Plus for both the EG‐1,2‐BDO binary mixture and the EG‐1,2‐BDO‐1,2‐PDO ternary mixture. The simulation results show that the azeotropic distillation method with CPO as an entrainer can effectively separate the mixture of EG‐1,2‐BDO and EG‐1,2‐BDO‐1,2‐PDO, achieving EG of 99.90% purity with 99.98% recovery and 1,2‐BDO of 99.30% purity with 99.45% recovery for the binary mixture, and achieving EG of 99.90% purity with 99.80% recovery, 1,2‐BDO of 99.35% purity with 99.35% recovery, and 1,2‐PDO of 90.59% purity with 94.38% recovery for the ternary mixture. These processes are promising for industrial application and can significantly improve the economy of non‐petroleum EG production.

Biological Buffer Effect on Liquid–Liquid Equilibria of Systems Containing n-Butanol + Methyl Isobutyl Ketone + Water

Biofuel, that is, n-butanol, production from plant-based biomass represents a renewable energy resource that can be a substitute for fossil fuel. Thus, it is important to study the separation of n-butanol from its aqueous solution to obtain a high-purity product. Liquid–liquid extraction is a beneficial process in alcohol production to recover alcohol from the aqueous medium. Liquid–liquid equilibrium (LLE) data are needed for rational design and optimal separation operation, such as biological separation and extraction processes. The objective of this study is to determine LLE data for quaternary systems of n-butanol, methyl isobutyl ketone (MIBK), water, and a biological buffer at 303.15 K and atmospheric pressure (P = 0.1 MPa). The effect of biological buffer addition into aqueous solution was also studied. Three different biological buffers, 4-(2-hydroxyethyl)-1-piperazine propanesulfonic acid (EPPS), 4-morpholinepropanesulfonic acid (MOPS), and 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES), were applied in this study for the comparison. The separation factor and distribution coefficient were evaluated in this study to interpret the extraction performance of n-butanol. According to the experimental results, the extraction performance was in the order of HEPES > EPPS > MOPS, describing the strength of buffering-out as well. Furthermore, it was found that the aid of a biological buffer in the LLE systems consisting of n-butanol, MIBK, and water resulted in better extraction performance than that of the LLE systems in the absence of a biological buffer. The reliability of the experimental LLE tie-line data was satisfactorily ascertained by the Hand correlation. The non-random two-liquid and universal quasi-chemical thermodynamics models correlated well the experimental LLE tie-line data with the root mean square deviation of less than 1%. The binary interaction parameters of both models were also obtained in this study.

Liquid–Liquid Equilibria for Pseudo-Ternary Systems of 1-Hydroxypropan-2-one + Water + Cyclic Terpene-Based Mixtures at 298.15 K

Herein, liquid–liquid equilibria (LLE) were investigated for pseudo-ternary systems comprising water + 1-hydroxypropan-2-one + cyclic terpene-based mixtures at 298.15 K and 0.1 MPa. Menthol/levulinic acid-, menthol/dodecanoic acid-, menthol/thymol-, thymol/decanoic acid-, thymol/10-undecenoic acid-, and menthol/decanoic acid-based mixtures were prepared in 1:2, 2:1, 1:1, 1:1, 1:1, and 1:1 molar ratios, respectively, which are type V deep eutectic solvents (DESs). The pseudo-ternary system separation factors were determined. When decanoic acid was used as a hydrogen bond donor, the menthol-based DES exhibited a higher separation factor than the thymol-based DES. Among the pseudo-ternary systems, menthol- and decanoic-acid-based DESs exhibited the highest separation factor. A non-random two-liquid (NRTL) model was used to regress the LLE data. The Gibbs-energy-of-mixing (GM/RT) surface was topologically analyzed to determine the tie line consistency. The experimentally measured and NRTL-modeled tie lines were tangential to the GM/RT surface curve, indicating that the minimum Gibbs free energy of mixing was satisfied at equilibrium points.