Liquid Equilibrium Research Articles

Polymer co-crystallization from LLE: Crystallization kinetics of POCB hydrate from two-phase mixtures of POCB and water

Polyoxacyclobutane (POCB, –[CH2CH2CH2O−]n) has the rare ability to co-crystallize with water to form a hydrate. Above the melting point of the hydrate (∼37 °C), mixtures exist in liquid-liquid equilibrium (LLE) between a POCB-rich and a water-rich liquid phase over a wide range of POCB:water ratios. Such phase behavior, which combines liquid-liquid equilibrium (LLE) and co-crystallization of a polymer with a small molecule, appears to be unique to POCB-water mixtures. Here, we examine the kinetics of isothermal hydrate co-crystallization when mixtures that are initially in liquid-liquid equilibrium (LLE) are cooled to below the hydrate melting point. Hydrate co-crystallization requires both POCB and water, and hence, it is coupled with transport of species between the liquid phases. Optical microscopy shows that hydrate crystallization occurs within the POCB-rich domains, and hydrate spherulites grow at constant speed. The temperature-dependence of the speed of hydrate growth front is consistent with the Hoffman Lauritzen model for homopolymer crystallization. Dilatometric measurements of bulk co-crystallization kinetics are conducted with constant stirring to avoid gravitational separation of the liquid phases. The temperature-dependence of bulk crystallization kinetics of these stirred mixtures in LLE is found to be far weaker than that of spherulitic growth kinetics, or of the quiescent bulk crystallization kinetics of mixtures starting from homogeneous conditions.

Liquid–Liquid Equilibria of Glycerol + Alcohol + Safflower Biodiesel Systems: Measurement and Modeling

Liquid–liquid equilibrium (LLE) for the biodiesel + glycerol + alcohol system is essential for the design, operation, process optimization, and economic evaluation of a biodiesel production plant. In this work, methyl and ethyl safflower biodiesels were produced from safflower (Carthamus tinctorius L.) seed oil. New LLE experimental datasets were obtained for the glycerol (1) + methanol/ethanol (2) + methyl/ethyl safflower biodiesel (3) systems at 298.15 and 318.15 K under atmospheric pressure. Binodal curves, tie-lines, distribution coefficients, and selectivity were determined. Data reliability was confirmed using the Othmer–Tobias correlation. LLE data were correlated with the UNIQUAC model satisfactorily, with deviations between 0.70 and 2.79% for all studied systems. The consistency of the estimated binary interaction parameters of the UNIQUAC model was ascertained. Finally, through process simulations in Aspen Hysys software, it was verified that the UNIFAC LLE model, along with the UNIQUAC model, can also be used adequately to describe the liquid–liquid behavior of biodiesel separators, provided that the biodiesel composition is accurately known.

A Neural-Network-Optimized Hydrogen Peroxide Pairwise Additive Model for Classical Simulations.

We have developed an all-atom pairwise additive model for hydrogen peroxide using an optimization procedure based on artificial neural networks (ANNs). The model is based on experimental molecular geometry and includes a dihedral potential that hinders the cis-type configuration and allows for crossing the trans one, defined between the planes that have the two oxygen atoms and each hydrogen. The model's parametrization is achieved by training simple ANNs to minimize a target function that measures the differences between various thermodynamic and transport properties and the corresponding experimental values. Finally, we evaluated a range of properties for the optimized model and its mixtures with SPC/E water, including bulk-liquid properties (density, thermal expansion coefficient, adiabatic compressibility, etc.) and properties of systems at equilibrium (vapor and liquid density, vapor pressure and composition, surface tension, etc.). Overall, we obtained good agreement with experimental data.

Correction to “Isobaric Vapor–Liquid Equilibrium Experiment of Methyl Acetate + Ethanol Containing Different Ionic Liquids at 101.3 kPa”

ADVERTISEMENT RETURN TO ARTICLES ASAPAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “Isobaric Vapor–Liquid Equilibrium Experiment of Methyl Acetate + Ethanol Containing Different Ionic Liquids at 101.3 kPa”Feihu LiFeihu LiMore by Feihu Lihttps://orcid.org/0000-0001-5624-4467, Jiaming ZhuJiaming ZhuMore by Jiaming Zhu, Xiwei HuXiwei HuMore by Xiwei Huhttps://orcid.org/0000-0002-4383-6030, Linjun SunLinjun SunMore by Linjun Sun, Hongkang ZhaoHongkang ZhaoMore by Hongkang Zhao, Zhongqi RenZhongqi RenMore by Zhongqi Ren, and Qunsheng Li*Qunsheng LiMore by Qunsheng Lihttps://orcid.org/0000-0002-1908-9418Cite this: J. Chem. Eng. Data 2023, XXXX, XXX, XXX-XXXPublication Date (Web):June 12, 2023Publication History Received31 May 2023Published online12 June 2023https://doi.org/10.1021/acs.jced.3c00329© 2023 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views-Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (698 KB) Get e-Alertsclose Get e-Alerts

Seawater desalination by forward-osmosis-assisted temperature swing solvent extraction

This study investigates seawater desalination by a combined process consisting of forward osmosis and temperature swing solvent extraction (TSSE). While direct desalination by temperature swing solvent extraction suffers from low extraction efficiencies, forward osmosis enables to transfer water into a more favourable salt solution expanding the amount of suitable solvents and increasing the subsequent extraction yield. In this work, tie lines of aqueous two-phase systems consisting of the thermoresponsive solvent polypropylene glycol 600 and different salts (NaCl, Na2SO4, MgSO4) were determined to investigate the influence of salt type, concentration, and temperature on the liquid-liquid equilibrium. Based on these results, MgSO4 (20 wt%) was selected as draw solute achieving water fluxes up to 7.5 Lm−2 h−1 in forward osmosis against artificial seawater. The diluted draw solution is regenerated by TSSE achieving high extraction yields (0.38 kgwater/kgsolvent). Eventually, the extracted water is separated from the solvent by temperature-induced phase separation at low temperatures enabling the use of low-grade thermal energy sources. In comparison to the direct use of the thermoresponsive polymer as draw agent, the proposed process benefits from significantly higher water fluxes due to reduced internal concentration polarization when using a salt based draw solution.

Convex Envelope Method for determining liquid multi-phase equilibria in systems with arbitrary number of components

The determination of liquid phase equilibria plays an important role in chemical process simulation. This work presents a generalization of an approach called the convex envelope method (CEM), which constructs all liquid phase equilibria over the whole composition space for a given system with an arbitrary number of components. For this matter, the composition space is discretized and the convex envelope of the Gibbs energy graph is computed. Employing the tangent plane criterion, all liquid phase equilibria can be determined in a robust way. The generalized CEM is described within a mathematical framework and it is shown to work numerically with various examples of up to six components from the literature.

Molecular mechanism and process of efficient separation of benzene and cyclohexane using a low-cost deep eutectic solvent

In this work, we propose a deep eutectic solvent (DES) extractant for the separation of benzene (BEN) and cyclohexane (CYH) with a lower price and higher separation performance. First, 50 hydrogen bond acceptors (HBAs) and 31 hydrogen bond donors (HBDs) were screened using the COSMO-RS model. We selected NH4SCN:Sulfolane (1:3) for its physical properties and predicted eutectic points, and prepared it as the extractant. To further explore the structure–activity relationship, we analyzed the separation mechanism between DESs and BEN at the atomic scale, by quantum chemistry and molecular dynamic simulation. In addition, the liquid–liquid equilibrium data of the ternary system BEN-CYH-NH4SCN:Sulfolane were experimentally determined and used to fit the parameters of the NRTL model. Based on the NRTL model, the extraction combined extractive distillation process was simulated. We show that compared with the traditional process, the energy consumption and TAC of this process show great advantages to existing approaches.

Liquid–Liquid Equilibrium Measurements and Interaction Explorations for Separation of Dimethyl Carbonate and Isopropyl Alcohol Using ChCl-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs) were adopted to separate the azeotropes of dimethyl carbonate (DMC) and isopropyl alcohol (IPA). Liquid–liquid equilibrium (LLE) data plays a crucial role in designing the separation process. Three appropriate DESs (choline chloride (ChCl)-Urea, ChCl-Glycerol (Gly), ChCl-Ethylene glycol (EG)) were selected using the COMSO model. Then, the LLE data of DMC-IPA-(ChCl-Urea), DMC-IPA-(ChCl-EG), and DMC-IPA-(ChCl-Gly) were obtained through experiments at 298.15 K under 101.32 kPa, the binary interaction parameters were obtained by regressing the LLE data by the nonrandom two-liquid (NRTL) model, and the GUI-Matlab was adopted to verify the precision of the NRTL interaction parameters and the experimental data. Finally, the mechanism of formation of the combined structures (DES-IPA/DMC) was explored through ESP. To further explore the extraction capacities of the selected DESs, the extraction mechanism of three DESs was revealed. The interactions between DESs and IPA/DMC were explored through penetration distance and AIM analysis; the calculation results showed that (ChCl-EG) has the best extraction capacity, which is consistent with the experimental results. The results of experimental and theoretical calculations showed that the DES could effectively separate DMC and IPA.

Separation of furfuryl alcohol from water using hydrophobic deep eutectic solvents

Furfuryl alcohol (FA) is an important organic chemical feedstock that must be separated from water to upgrade it into high-value-added products. Since FA forms an azeotrope with water, liquid-liquid extraction is a suitable option for separating both compounds. This work evaluates the separation of FA from water using hydrophobic deep eutectic solvents (DES). Three DES were prepared using menthol, thymol, and octanoic acid by combining them in molar ratio as follows: thymol + octanoic acid (1:2), menthol + octanoic acid (1:2), and thymol + menthol (1:1). Experimental liquid-liquid equilibria (LLE) of ternary systems water + FA + DES measured at 313.15 K and 101.13 kPa were used to determine the distribution coefficient and selectivity values for FA when using each DES. The experimental results were compared with molecular dynamics (MD) using Martini 3 force field and modeled using Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) without any adjustable binary parameters. According to the results, selectivities and distribution coefficients using hydrophobic DES have comparable values to traditional volatile organic compounds (VOCs) used to separate FA from water. In general, DES shows better distribution coefficients compared with typical organic solvents. According to the results, a good alternative would be menthol + octanoic acid (1:2) or thymol + menthol (1:1) to replace typical VOCs. MD and PC-SAFT provide accurate estimations for ternary LLE in the range of examined thermodynamic conditions, which confirms the predictive consistency of both approaches. Microscopic properties computed with MD simulations evidence a surface activity or absolute adsorption of FA in the interfacial region, which is correlated with favorable distribution coefficients and selectivities.

Liquid–liquid phase separation in binary mixtures of quaternary alkylammonium chlorides with carboxylic acids

We reported the phase separation measurements of mixtures obtained from choline, tetramethylammonium and tetraethylammonium chlorides with methacrylic (MAA), butyric (BA) and isobutyric (IBA) acids as solvents. Liquid-liquid equilibrium (LLE) experiments were performed under atmospheric pressure in a temperature range of 287–403 K using cloud-point method and the data were correlated with the Non-Random Two Liquid (NRTL) solution model. The density, the viscosity, the Kamlet-Taft and the solvent polarity (ET(30)) parameters were measured for coexisting liquid phases. The applicability of the obtained binary biphasic system in extraction process, particularly purification of MAA from a phenolic inhibitor, was demonstrated.

Extraction of C6 α-olefin against n-paraffin in coker naphtha with deep eutectic solvents: Quantum chemical calculations and experimental investigation

Extraction technology is often employed to separate olefin/paraffin mixtures due to the advantages of mature process, flexible operation, and large processing capacity. This work aims to investigate the effectiveness of novel deep eutectic solvents (DESs) for the extraction of 1-hexene/n-hexane model coker naphtha using a combination of simulations and experiments. The results showed that the aliphatic or aromatic groups in the hydrogen bond acceptors or hydrogen bond donors have a strong affinity for 1-hexene, and the components containing hydroxyl or aromatic groups possess the ability to provide protons, which is beneficial to dissolve 1-hexene. Combining the results of the melting point predicted by the group and group-interaction contribution model, three DESs, namely ethanolamine-sulfolane 1:5 (DES1), tetrabutylammonium bromide-bis[2-(2-hydroxyethoxy)ethyl] ether 1:4 (DES2), and methyltriphenylphosphonium bromide-Triethylene glycol 1:4 (DES3), were finally prepared. Then, quantum chemical calculations were used to investigate the separation mechanism between the DESs and 1-hexene/n-hexane, demonstrating single-center and multi-center hybrid weak hydrogen bonds dominated by the dispersion attraction between DESs and 1-hexene. Finally, liquid–liquid equilibrium experiments were used to examine the effects of DESs type, composition, and temperature on the separation performance, and the results showed that the DES1 has both high distribution coefficient of 1-hexene and selectivity of 1-hexene/n-hexane, as well as good recycle stability. This work demonstrates that new DESs can be used as alternative solvents to traditional organic solvents and ionic liquids, and provides ideas for the separation of olefins and paraffins in coker naphtha.

Liquid-liquid equilibrium of CO2/bitumen and CO2/bitumen/ethyl acetate systems with application to diluted bitumen transportation

Bitumen transportation by pipelines requires dilution with solvents. These diluents are often expensive. Therefore, the utilization of liquid CO2 as a diluent to reduce or eliminate diluent consumption is of interest. However, there is limited data in the literature on the liquid-liquid equilibrium (LLE) of CO2 and bitumen. In this work, we report a new set of LLE data for MacKay River bitumen and liquid CO2 at ambient temperature. First, the LLE of bitumen/CO2 at various CO2 feed concentrations was studied. The density of light and heavy liquid phases, the viscosity of the heavy phase, and the heavy phase volume fraction were measured. It was shown that a CO2 feed concentration of 30 wt% is optimum for achieving maximum dissolution of CO2 in bitumen. Then, the effect of pressure on the LLE of bitumen/CO2 at a 30 wt% CO2 concentration was studied. The results revealed a significant reduction in bitumen viscosity from 300,000–1250 cP could be achieved at 21 °C. The results suggest that liquid CO2 can be utilized to reduce diluent consumption in pipeline transportation. The role of ethyl acetate (EA) as a co-solvent with CO2 was also examined. It was shown that the addition of EA to a mixture of bitumen/CO2 could further reduce the bitumen viscosity to satisfy the pipeline transportation criterion. The results reveal that CO2-assisted bitumen transportation in Canada can lead to the utilization of 0.16 Mt of CO2 daily, which is equivalent to a utilization potential of about 80 kg CO2/bbl of raw bitumen. The results also suggest a 73% reduction in fossil-based diluent usage, equivalent to ∼0.5 million barrels of crude oil.

Liquid–Liquid Equilibrium Measurement and Thermodynamic Modeling for Ternary Systems of 2-Ethyl-1-hexanol + 1,2-Propanediol + (Water and n-Heptane) at Different Temperatures

To recover 2-ethyl-1-hexanol and 1,2-propanediol from waste polyester alcoholysis products, liquid–liquid equilibrium (LLE) data for the ternary system of 2-ethyl-1-hexanol + 1,2-propanediol + (water, n-heptane) at different temperatures (303.2, 313.2, and 323.2 K) were studied at 101.3 kPa. The distribution coefficient (D) and selectivity coefficient (S) were used as indicators to assess the separation effect. The NRTL and UNIQUAC models were used to correlate the experimental data and the root mean square deviation (RMSD) values were calculated to be less than 0.75 and 0.97%, respectively. Finally, the consistency between the experimental data and the regression parameters was verified using the GUI-MATLAB tool. σ-Profiles are used to discuss the interactions of substances in this work. It was found that both extractants could separate and extract 2-ethyl-1-hexanol and 1,2-propanediol effectively, with water being more effective.

Impact of extended long-range electrostatics on the correlation of liquid-liquid equilibria in aqueous ionic liquid systems

Impact of extended long-range electrostatics on the correlation of liquid-liquid equilibria in aqueous ionic liquid systems

Analysis of the Composition and Formation Mechanism of Fouling in the Concentration Process of Titanium White Waste Acid

Large quantities of titanium white waste acid (TWWA) are generated during TiO2 production by the sulfate process. Recycling by concentration is the most widely used method to treat TWWA. However, serious fouling occurs during this process. The chemical composition of fouling obtained from a commercial plant was analyzed. The phase equilibria of CaSO4-FeSO4-H2SO4-H2O at 373.15 and 378.15 K were studied to elucidate the fouling mechanism. The fouling was mainly composed of CaSO4 (anhydrite) (74.97 wt %) and TiO(OH)2 (anatase) (24.48 wt %). The mass fractions of CaSO4 and FeSO4 in the equilibrium liquid phase of the CaSO4-FeSO4-H2SO4-H2O system increased with an increase in temperature and a decrease in H2SO4 concentration. The Pitzer method was successfully employed to describe the equilibrium behavior. During the mixing of the recycled acid and the initial TWWA, some CaSO4 (anhydrite) precipitated from the liquid phase, while some FeSO4·H2O dissolved in the liquid phase during the mixing and heating process. In the heating process, CaSO4 (anhydrite) did not precipitate out from the liquid phase. It was thus concluded that CaSO4 (anhydrite) precipitation during the mixing process is the key factor for the fouling on the heat exchanger surface during the primary evaporation process.

Investigation of Solid–Liquid Phase Equilibria of Mg2+, NH4+//Cl–, SO42–H2O at T = 303.15 K and P = 88.35 kPa

Nitrogen and magnesium compound fertilizer is an important and efficient fertilizer in the fertilizer industry. It can solve the problem of lack of sulfur, magnesium, and nitrogen in soil. MgCl2 can react with (NH4)2SO4 to produce Mg–N compound fertilizer. Therefore, the solid–liquid equilibrium data and physical properties (density and viscosity) of the quaternary system Mg2+, NH4+//Cl–, SO42––H2O and its ternary subsystems Mg2+, NH4+//Cl––H2O and Mg2+//Cl–, SO42––H2O at T = 303.15 K ± 0.05 K and P = 88.35 kPa were studied by an isothermal stripping equilibrium method. According to the experimental data, the phase diagram and physical property composition diagram of each system were drawn. The ternary subsystem Mg2+, NH4+//Cl––H2O contains two invariant points and three crystallization regions. The ternary system Mg2+//Cl–, SO42––H2O contains four invariant points and five crystallization regions. The quaternary system Mg2+, NH4+//Cl–, SO42––H2O contains seven invariant points and nine crystallization regions. MgCl2·NH4Cl·6H2O and MgSO4·(NH4)2SO4·6H2O exist in the quaternary system, and the quality of crops can be significantly improved by using the latter kind of complex salt. Therefore, this project is of great significance for the production of N–Mg compound fertilizers from magnesium resources in salt lake or other underground brines.

Vapor-liquid equilibrium for the binary mixed refrigerant {R1234ze(E) + R1336mzz(E)} at temperatures from 283.15 K to 313.15 K

Growing concerns regarding energy and environmental issues have prompted the development of refrigerants focused on energy conservation and environmental protection. Mixed refrigerants incorporating fourth-generation hydrofluoroolefins (HFOs) represent a promising advancement. Notably, R1234ze(E) and R1336mzz(E) are representative examples of environmentally friendly refrigerants within the HFO category. In this study, a vapor–liquid equilibrium (VLE) experimental apparatus was constructed based on the liquid-phase cycling method, and the VLE data for eleven R1234ze(E) + R1336mzz(E) mixed refrigerants with varying proportions were measured within the temperature range of 283.15 ∼ 313.15 K. In addition, all the experimental data were correlated using two models: the Peng-Robinson (PR) equation of state combined with the van der Waals (vdW) mixing rule, and the PR equation of state combined with the Huron-Vidal (HV) mixing rule involving the non-random two-liquid (NRTL) activity coefficient. The results indicate that R1234ze(E) + R1336mzz(E) mixed refrigerants do not exhibit azeotropic behavior within the studied temperature range. Furthermore, both the PR + vdW and PR + HV + NRTL models show good agreement with the experimental data, with the latter model demonstrating superior performance.

Extractive desulfurization of thiophene by tetraethylene glycol at T = 298.15 to 313.15 K and liquid–liquid phase equilibrium study

ABSTRACT This study provides the complete liquid–liquid equilibrium (LLE) data including the solubility curves and tie-lines for heptane + thiophene + tetraethylene glycol and cyclohexane + thiophene + tetraethylene glycol ternary mixtures at 298.15–313.15 K under a pressure of 83.4 ± 1 kPa. The experimental data were obtained by the cloud point method. Type 1 phase behavior is observed for the systems. The observed behavior was interpreted based on the type and nature of the interactions between the components. The capability of tetraethylene glycol in extractive desulfurization of thiophene from liquid fuel is evaluated by determining the solute distribution coefficient and selectivity. The high values of the selectivity show that tetraethylene glycol is a good candidate for this purpose. The investigation of the effect of temperature on the area of the biphasic region and distribution ratios shows that the extraction process can be performed at room temperature. The experimental data were successfully correlated with the NRTL model. The reliability of the correlation results was checked by using a Graphical User Interface (GUI) for the representation of Gibbs energy of mixing (GM). The root mean square deviation (RMSD), a measure of the precision of the correlations, ranges from 0.0022 to 0.0040.

Activity coefficient acquisition with thermodynamics‐informed active learning for phase diagram construction

AbstractThis work explores the use of thermodynamics‐informed Gaussian processes (GPs) and active learning (AL) to model activity coefficients and construct phase diagrams. Relying on synthetic data generated from an excess Gibbs energy model, GPs were found to accurately describe the activity coefficients of several binary mixtures across large composition and temperature ranges. Moreover, GPs could estimate their own uncertainty and identify composition/temperature regions where activity coefficient data provide the most information to the models. This was leveraged to build AL algorithms targeted at modeling phase equilibria. In many cases, a single active‐learning‐acquired data point was sufficient to describe the phase diagrams studied. Finally, the ability of AL to greatly reduce the amount of data needed to obtain accurate models was further verified on experimental case studies, namely individual ion activity coefficients, the solid–liquid and vapor–liquid equilibrium of deep eutectic solvents, and phase equilibria in ternary mixtures.

Methane Storage in Simulated Seawater Enabled by 1,3-Dioxane as an Environmentally Benign Promoter

With the ever-increasing demand for natural gas (NG) in the current century, solidified natural gas (SNG) technology is bound to play an indispensable role in enhancing energy resilience and ensuring sufficient energy supply globally. Herein, dioxane was employed as not only an environmentally benign additive but also a dual-function (thermodynamic and kinetic) promoter for hydrate formation in simulated seawater. This approach helps bypass the issue of water scarcity, avoids the utilization of toxic and volatile chemicals, and carries the potential to enhance the methane storage capacity. The three-phase (gas, liquid, and hydrate) equilibrium conditions were measured for mixed CH4/dioxane hydrate formation in simulated seawater. Extensive experiments were conducted at a constant temperature of 283.2 K and various initial pressures (7.5, 9.5, and 11.5 MPa) to investigate the impact of the initial experimental pressure on the kinetics of mixed CH4/dioxane hydrate formation in simulated seawater. Additionally, the application of l-tryptophan (1000 ppm) as a co-promoter or an additional kinetic promoter for the process was studied. At an initial pressure of 11.5 MPa, up to 93.57 (±4.33) v/v methane storage capacity was achieved in simulated seawater containing 5.56 mol % dioxane, while upon the addition of l-tryptophan to the system, the hydrate formation rate at the same initial pressure was increased over 6-fold from 0.51 (±0.08) to 3.13 (±0.06) v/v min–1. The analysis of in situ Raman spectra confirmed the exclusive formation of structure II methane hydrate, despite the formation of structure I methane hydrate being possible from the thermodynamic point of view. The results obtained in the current work contribute to the development of SNG technology via the utilization of seawater.