Liquid Equilibrium Research Articles

Solubility of K2SO4, Li2SO4, and (NH4)2SO4 in mixtures of water and methanol at different temperatures: Experimental and application of the modified Pitzer model

The study of electrolyte solutions is crucial for various industrial sectors. A thorough understanding of the solid–liquid equilibrium associated with mathematical models is necessary for the separation and purification of these materials, as well as for developing solution theories and process simulators. This study focuses on the solubility of K2SO4, Li2SO4, and (NH4)2SO4 in binary liquid solutions of water and methanol, at temperatures ranging from 283.2 K to 323.2 K. The results show that as the concentration of methanol increases, solubility decreases drastically while increasing temperature leads to an increase in solubility (except for Li2SO4). The modified Pitzer model was successfully applied to describe the solid–liquid equilibrium, and it also explained the salting-out precipitation by the addition of an antisolvent.

Study on separation of methanol and dimethyl carbonate azeotropic system with deep eutectic solvents

Dimethyl carbonate (DMC) is an important diesel and gasoline additive that is also a low-toxic and environmentally friendly chemical raw material. However, it will form an azeotrope with methanol (MeOH) during the actual chemical production process. Therefore, separating high-purity DMC from the azeotrope is of significance. In extractive distillation, deep eutectic solvents (DESs) have demonstrated superior separation performance as green extractants. This study calculated the σ-profiles of DMC, MeOH, and DESs by the COSMO-SAC model to examine the most appropriate DES for the MeOH and DMC separation. Eventually, DES1(1:2 choline chloride (ChCl): malonic acid (MA)), DES2(1:2 ChCl: urea), DES3(1:2 ChCl: glycerol (G)), DES4(1:2 ChCl: ethylene glycol (EG)), DES5(1:2 ChCl: pyruvic acid (PA)) were designated as preferred extractants. The vapor pressures of five DESs at different temperatures were determined using a thermogravimetric analyzer, while their critical properties, normal boiling points, and acentric factors were predicted. The vapor–liquid equilibrium (VLE) data measured for DMC + MeOH + DESs ternary systems at 101.3 kPa showed that the addition of 15 mol % of any of the five DESs could successfully break the azeotrope and DES2 achieved a higher degree of separation in the MeOH-DMC binary azeotrope compared to the other DESs evaluated. The binary interaction parameters between MeOH/DMC and DESs were calculated through the NRTL (Non-Random Two-Liquid) model, and the fitting results were found to be consistent with the experimental data. The mechanism of the MeOH-DMC separation by DES2 was elucidated through quantum chemical (QC) calculations. The improved independent gradient model (IGMH) and the theory of atoms in molecules (AIM) demonstrated that the stronger interaction between DES2 and MeOH molecules is the key for DES2 to break the azeotrope of the system.

Oiling-Out: Insights from Gibbsian Surface Thermodynamics by Stability Analysis.

The crystallization process is a significant stage in the pharmaceutical industry. During the process of crystallization with cooling, it is possible for a secondary liquid phase to appear before the formation of crystals. This phenomenon is called "oiling out" or liquid-liquid phase separation (LLPS). In this article, we explore the oiling-out phenomenon in a binary system of water and vanillin using stability analysis based on Gibbsian surface thermodynamics. To obtain the full picture of oiling out, we investigated three cases: droplet-solute-lean liquid equilibrium (DLE), crystal-solute-rich liquid equilibrium (CL'E), and crystal-solute-lean liquid equilibrium (CLE). The phase diagram of the system is plotted using the NRTL model for activity coefficients, along with considering the effect of the interfacial curvature on the phase diagram. From the phase boundaries and free-energy diagram of each case, we showed that the occurrence of the oiling-out phenomenon is justified based on the lower energy barrier of the droplet formation compared to that of the crystal formation. However, the energy level of a stable crystal is significantly lower and hence more stable than that of a stable droplet. Finally, we have determined different regions for droplet and crystal formation in the metastable phase diagram based on their supersaturation and provide insight for the oiling-out phenomenon.

Measurement and Correlation of Liquid–Liquid Equilibrium Data for Ternary Systems Water + C1–C3 Alcohols + Diethyl Adipate at 298.15 K and Atmospheric Pressure

Measurement and Correlation of Liquid–Liquid Equilibrium Data for Ternary Systems Water + C1–C3 Alcohols + Diethyl Adipate at 298.15 K and Atmospheric Pressure

Measurement and Correlation of Liquid–Liquid Equilibrium for the Ternary System 1-Octyl-3-methylimidazolium Tetrafluoroborate + 1-Ethyl-3-methylimidazolium Tetrafluoroborate + Water

Measurement and Correlation of Liquid–Liquid Equilibrium for the Ternary System 1-Octyl-3-methylimidazolium Tetrafluoroborate + 1-Ethyl-3-methylimidazolium Tetrafluoroborate + Water

Phase behavior and intermolecular interaction analysis of the ternary system of water + 2-methylpyridine + octanols from 303.2 K to 323.2 K

Wastewater from coking and pharmaceutical processes often contain a significant amount of 2-methylpyridine, which forms an azeotropic mixture with water. Effectively and cleanly separating 2-methylpyridine from wastewater while conserving energy and obtaining high purity products is an urgent challenge. In this study, ternary liquid-liquid equilibrium (LLE) data for the extraction of 2-methylpyridine from wastewater were measured using three distinct solvents at temperatures of 303.2 K, 313.2 K, and 323.2 K. The obtained ternary data were subsequently correlated with thermodynamic models (NRTL and UNIQUAC) to get relevant binary interaction parameters, bridging a gap in Aspen Plus simulations of 2-methylpyridine separation by octanol solvents. Furthermore, the GUI tool was used to validate these parameters and the results confirmed the reliability of the obtained parameters. It was observed that as the temperature increased, the extraction performance of all systems decreased, indicating that elevated temperature are not conducive to the extraction process. Among the various components, iso-octanol showed the highest separation factor indicating better extraction efficiency of 2-methylpyridine. Additionally, this study integrated quantum chemical calculations to reveal the interaction mechanisms between different solvents, 2-methylpyridine, and water at the microscopic level. The computational results indicated that iso-octanol exhibited the most robust binding affinity with 2-methylpyridine, suggesting that iso-octanol has more excellent extraction properties.

Ternary (Liquid–Liquid) Equilibrium Experiment and Thermodynamic Modeling for Extraction of Phenol from Water with Different Solvents at Several Temperatures

Ternary (Liquid–Liquid) Equilibrium Experiment and Thermodynamic Modeling for Extraction of Phenol from Water with Different Solvents at Several Temperatures

Customizable cholinium-based aqueous biphasic systems as ecofriendly extraction platform for removal of pesticide from wastewaters

This study explores the use of a series of cholinium ionic liquids (ILs) or salts in combination with polypropylene glycol 400 to form aqueous biphasic systems (ABS) for extracting various polarity pesticides (dicamba, clomazone, pyraclostrobin, and deltamethrin) from water. We assessed five cholinium-based salting-out agents ([Ch][DHP], [Ch]Cl, [Ch][Ac], [Ch][Lac], and [Ch][Nic]), chosen for their structural diversity and unique properties, such as high salting-out potential and different ability to undergo specific interactions. Liquid-liquid equilibrium phase diagrams were established, and partition experiments were conducted to evaluate extraction efficiency. Different partition patterns were obtained for studied pesticides, with [Ch][DHP] demonstrating the highest efficiency exceeding 90 % for each target pesticide due to its strong salting-out ability. On the other hand, more diverse partition trends due to specific interactions were obtained for low-melting cholinium-ILs ABS. The effect of pH and temperature on the partitioning behavior in [Ch][Ac]-based ABS highlighted the cholinium ILs extraction system's customizable nature. Focusing on [Ch]Cl for its eco-friendly aspects, widespread availability and excellent extraction performance, we optimized parameters for the removal of pesticides from real samples, applying the technology to spiked agricultural wastewater with an extraction efficiency of over 99 %. Our findings demonstrate the potential of cholinium-based IL-ABS in reducing environmental pollution through efficient pesticide extraction.

Salt Effects on the Phase Behavior and Cocrystallization Kinetics of POCB-Water Mixtures.

Mixtures of water with polyoxacyclobutane (POCB) have a unique phase diagram which combines liquid-liquid equilibrium (LLE) at high temperatures and cocrystallization of a POCB-hydrate at low temperatures. Such cocrystal hydrate formation is extremely rare among polymers. We report on the effects of adding NaCl salt on the phase behavior of POCB-water mixtures and the kinetics of hydrate crystallization from such mixtures. Salt loadings of less than 0.1 wt % were found to greatly expand the LLE region. Salt loadings of ∼10 wt % were found to significantly decrease the melting temperature of the hydrate below its ∼37 °C value under salt-free conditions. The hydrate was found to be remarkably tolerant of salt and persists at room temperature even when equilibrated with salt-saturated water. Salt was found to slow down hydrate crystallization, and the degree of slowing was greater than that expected from the salt-induced decrease in undercooling due to melting point depression.

Solid–Liquid Phase Equilibrium: Alkane Systems for Low-Temperature Energy Storage

The thermal characterization of two binary systems of n-alkanes that can be used as Phase Change Materials (PCMs) for thermal energy storage at low temperatures is reported in this work. The construction of the solid–liquid binary phase diagrams was achieved using differential scanning calorimetry (DSC) and Raman spectroscopy. The solidus and liquidus equilibrium temperatures were determined using DSC for thirty-nine different samples, three for the pure n-alkanes and the remaining for binary mixtures at selected molar compositions and used to acquire the corresponding solid–liquid phase diagrams. The two binary systems of n-octane/n-decane (C8/C10) and n-decane/n-dodecane (C10/C12) are characterized by a eutectic behavior at low temperatures. The eutectic temperature for the system C8/C10 was found at 211.95 K and the eutectic composition appeared at the molar fraction xoctane = 0.87. For the system C10/C12, the eutectic temperature was found at 237.85 K, and the eutectic composition appeared for the molar fraction xdecane = 0.78. This work aims to fulfill the lack of available data in the existing literature, considering the potential application of these systems for low-temperature thermal energy storage. Raman spectroscopy was used to complement the DSC data for the construction of the solid–liquid phase equilibrium diagrams, enabling the identification of the solid and liquid phases of the system. Additionally, the liquidus curve of the phase diagram was successfully described using a modified freezing point depression curve as fitting equation, the absolute root mean square deviation for the data correlation of the C8/C10 and C10/C12 systems being 2.56 K and 1.22 K, respectively. Ultimately, the fitting procedure also enabled a good prediction of the eutectic point for both studied systems.

Phase diagram of muonium hydride: the significant effect of dimensionality

We carry out a theoretical investigation of the low-temperature phase diagram of muonium hydride in two dimensions, using numerical simulations. It is shown that the phase diagram of this substance is qualitatively different in two and three dimensions. Specifically, while in three dimensions it is essentially identical to that of parahydrogen, i.e., only displaying a single (crystalline) phase. In two dimensions it is very similar to that of 4He, with an equilibrium liquid phase that turns superfluid at a temperature as high as ∼2.2 K, and crystallizes under applied pressure. This is a well-described case of a continuous-space condensed matter system whose ground state equilibrium phase is qualitatively altered by dimensional reduction.

Experimental and Theoretical Exploration of Liquid–Liquid Equilibrium of Ternary Mixtures (Water + Lactic Acid + Esteric Solvents) at T = 298.2 K

Experimental and Theoretical Exploration of Liquid–Liquid Equilibrium of Ternary Mixtures (Water + Lactic Acid + Esteric Solvents) at <i>T</i> = 298.2 K

Liquid–Liquid Equilibrium for the Ternary System of Water, Methyl Acrylate, and Different Solvents at 303.2 K under 101.3 kPa

Liquid–Liquid Equilibrium for the Ternary System of Water, Methyl Acrylate, and Different Solvents at 303.2 K under 101.3 kPa

Sustainable synthesis and extraction of 5-methyl-N-phenyl-2-pyrrolidone produced via reductive amination of levulinic acid

5-methyl-N-substituted-2-pyrrolidones (5MPs) have been proposed as alternatives to N-methyl-2-pyrrolidone, a solvent with industrial and commercial applications which is considered hazardous and undesired by regulators. 5MPs are produced via reductive amination of levulinic acid with a catalyst and a reducing agent like H2. However, the separation of 5MPs from the reaction media is scarcely studied to understand industrial and commercial viability. This work is centered on producing 5-methyl-N-phenyl-2-pyrrolidone from levulinic acid via reductive amination followed by its liquid–liquid extraction using specifically selected extracting solvents. The extraction step considers not only the separation performance but also the environmental, health, and safety (EHS) criteria of the selected solvents. Thus, COSMO-RS, along with EHS guides, were used to screen solvents to extract 5-methyl-N-phenyl-2-pyrrolidone from methanol or water, which are used as reaction solvents. Some promising extracting solvents were studied in ternary liquid–liquid equilibrium experiments based on the partition of 5-methyl-N-phenyl-2-pyrrolidone and the reactants in the extracting solvent + (water or methanol) biphasic system. Subsequently, the solvents were tested for the extraction of the 5-methyl-N-phenyl-2-pyrrolidone from a real reaction mixture, produced by a Pt/TiO2 catalyzed reductive amination at 25 °C and 1.013 bar. Predictions and further validations of the distribution coefficients and selectivities for the solute show that anisole and limonene are favorable solvents for extracting 5-methyl-N-phenyl-2-pyrrolidone from water and methanol media, respectively. Both solvents are attractive alternatives due to their biobased nature, with the former ranked as recommended by EHS guides and the latter having some concerns with environmental criteria. However, both solvents show advantages for a scale-up of the reaction + separation process.

Thermal stability and vapor-liquid equilibrium of aqueous solutions of choline and tetramethylammonium taurate

The thermal degradation of tetramethylammonium taurate and choline taurate and aqueous solutions of these compounds were examined. The thermal degradation products for each of the solid compounds are identified and the data show that the compounds lose less than 1 % of their mass when heating is below 85 °C for 10 h. However, it is difficult to distinguish between the degradation of the compounds and the loss of strongly retained water. The degradation products of the compounds in aqueous solution are also identified and a degradation pathway is proposed. Additionally, the vapor–liquid equilibrium of the compounds in aqueous solutions was measured and the data was fit to the non-random two-liquid (NRTL) model. The data indicate significant deviations from ideality as described by the activity coefficients of the solutions. The results provide insight into the selection of absorber stripping temperatures, the modeling of absorber columns that utilize aqueous ionic absorber fluids, and how these properties are impacted by different cations.

Revealing Solid–Liquid Equilibrium Behavior of 4-Fluorobenzoic Acid in 12 Pure Solvents from 283.15 to 323.15 K by Experiments and Molecular Simulations

Revealing Solid–Liquid Equilibrium Behavior of 4-Fluorobenzoic Acid in 12 Pure Solvents from 283.15 to 323.15 K by Experiments and Molecular Simulations

Liquid–Liquid Equilibrium for Ternary Systems of Water, Methacrylic Acid, and Alkyl Alcohols: Thermodynamic Analysis and Solvent Comparison

Liquid–Liquid Equilibrium for Ternary Systems of Water, Methacrylic Acid, and Alkyl Alcohols: Thermodynamic Analysis and Solvent Comparison

Determination and correlation of LLE data for n-hexane, ethyl acetate and different extractants

In order to separate n-hexane/ethyl acetate (EA) produced in industrial production, the liquid–liquid extraction was used to separate the azeotropic system with sulfolane, 1,2-propanediol and dimethyl sulfoxide (DMSO) as extractants. The liquid–liquid equilibrium (LLE) data of the n-hexane + EA + sulfolane/1,2-propanediol/DMSO were measured at 303.15 K, 313.15 K and 323.15 K. The extraction capacity of the extractants were evaluated by the distribution coefficient (D) and separation factor (S). The LLE data were correlated using the NRTL and UNIQUAC thermodynamic models to obtain binary interaction parameters. The root mean square deviation (RMSD) were all less than 0.02 indicating that the two models were suitable for the phase equilibrium behavior. GUI-MATLAB software was used to test the reliability of the regressed binary interaction parameters. The Dmol3 module of the Materials Studio was used to analyze σ-profile of n-hexane, EA and extractants and to assess the interaction energy between the components. The results show that sulfolane is the best extractant for the separation of n-hexane + EA.

Thermodynamics of Liquid Alloys and Vapor–Liquid Equilibrium in the Antimony–Tellurium System

The partial and integral thermodynamic functions of formation and evaporation of antimony-tellurium melts were calculated based on the vapor pressure values of the components in the Sb–Sb2Te3 and Sb2Te3–Te systems. It is shown that integral functions of evaporation enthalpy and entropy insignificantly change in value from the alloy corresponding to the Sb2Te3 composition and slightly decrease in the direction of antimony and tellurium on the state diagram. However, they can be described by a linear dependence in the entire concentration interval of solutions existence within the experiment error. The boundaries of liquid and vapor coexistence fields at atmospheric pressure (101.3 kPa) and in vacuum (0.9 kPa) were calculated based on the partial pressure values of melt components. It is shown that the separation of antimony alloys with tellurium by distillation into elements at atmospheric pressure is difficult because of high boiling temperatures of antimony-based alloys. It would require a significant number of condensate re-evaporation cycles in a vacuum. The results aim at creating the fundamental physical and chemical foundations of the distillation technologies for processing melted chalcogenide systems. The second aim is to issue effective practical recommendations necessary for developing and improving the process of extracting rare metals from polymetallic mattes by vacuum-thermal method.Graphical

Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane

Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane