Phase Equilibria Of Ternary Mixtures Research Articles

Mutual Diffusivities of Mixtures of Carbon Dioxide and Hydrogen and Their Solubilities in Brine: Insight from Molecular Simulations.

H2-CO2 mixtures find wide-ranging applications, including their growing significance as synthetic fuels in the transportation industry, relevance in capture technologies for carbon capture and storage, occurrence in subsurface storage of hydrogen, and hydrogenation of carbon dioxide to form hydrocarbons and alcohols. Here, we focus on the thermodynamic properties of H2-CO2 mixtures pertinent to underground hydrogen storage in depleted gas reservoirs. Molecular dynamics simulations are used to compute mutual (Fick) diffusivities for a wide range of pressures (5 to 50 MPa), temperatures (323.15 to 423.15 K), and mixture compositions (hydrogen mole fraction from 0 to 1). At 5 MPa, the computed mutual diffusivities agree within 5% with the kinetic theory of Chapman and Enskog at 423.15 K, albeit exhibiting deviations of up to 25% between 323.15 and 373.15 K. Even at 50 MPa, kinetic theory predictions match computed diffusivities within 15% for mixtures comprising over 80% H2 due to the ideal-gas-like behavior. In mixtures with higher concentrations of CO2, the Moggridge correlation emerges as a dependable substitute for the kinetic theory. Specifically, when the CO2 content reaches 50%, the Moggridge correlation achieves predictions within 10% of the computed Fick diffusivities. Phase equilibria of ternary mixtures involving CO2-H2-NaCl were explored using Gibbs Ensemble (GE) simulations with the Continuous Fractional Component Monte Carlo (CFCMC) technique. The computed solubilities of CO2 and H2 in NaCl brine increased with the fugacity of the respective component but decreased with NaCl concentration (salting out effect). While the solubility of CO2 in NaCl brine decreased in the ternary system compared to the binary CO2-NaCl brine system, the solubility of H2 in NaCl brine increased less in the ternary system compared to the binary H2-NaCl brine system. The cooperative effect of H2-CO2 enhances the H2 solubility while suppressing the CO2 solubility. The water content in the gas phase was found to be intermediate between H2-NaCl brine and CO2-NaCl brine systems. Our findings have implications for hydrogen storage and chemical technologies dealing with CO2-H2 mixtures, particularly where experimental data are lacking, emphasizing the need for reliable thermodynamic data on H2-CO2 mixtures.

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.

Solid–Liquid Phase Equilibria of Ternary Mixtures Containing 1,2-Dihydroacenaphthylene and Dibenzofuran

Ternary phase diagram data of 1,2-dihydroacenaphthylene-dibenzofuran mixtures in a series of alcohols, including methanol, ethanol, propan-2-ol, propan-1-ol, butan-1-ol, and pentan-1-ol were measured using a dynamic method at 308.15 and 313.15 K. The experimental data were correlated with the Wilson model (including pseudobinary systems), UNIQUAC model, and NRTL model. The results indicate that pseudobinary systems with the Wilson equation give a better description of the solubility of the ternary system. The eutectic point shifts toward dibenzofuran when the more polar methanol and ethanol are used. This shift may help achieve a more efficient separation of 1,2-dihydroacenaphthylene and dibenzofuran.

Non-invasive quantification of phase equilibria of ternary mixtures composed of carbon dioxide, organic solvent and water

Raman spectra of ternary mixtures of unknown composition are processed to extract the content of the compounds in the mixture. The evaluation method of the ternary mixtures is based on a previous calibration of binary mixtures. The applicability of the method is demonstrated by measuring the vapour liquid equilibria of the ternary system carbon dioxide, ethyl acetate and water at 8.5MPa and 310K and providing them in a triangle diagram. The advantages of the used flexible Raman sensor in comparison to conventional techniques for the determination of phase equilibria are discussed.

Phase Equilibria in Ternary Mixtures of Methyl Oleate, Glycerol, and Methanol

Transesterification reactions are common in the production of some important chemicals, such as biodiesel and mono- and diglycerides. Knowledge of the phase equilibrium conditions of the reactive mixture is essential to explore possible operating conditions for the reactor and the downstream separation process. In this work, liquid—liquid and vapor—liquid—liquid equilibrium data have been measured for the ternary system methyl oleate—methanol—glycerol, at temperatures between 313 and 393 K. The group contribution with association equation of state (GCA-EOS) and the A-UNIFAC model were applied to represent the phase equilibria of this ternary system. Self-association in glycerol and methanol and cross-association with methyl esters were taken into account.

Vapour-liquid equilibrium of ternary mixtures of the refrigerants R32, R125 and R134a

Ternary mixtures of R32, R125 and R134a of different compositions are recommended for replacing refrigerants R22 and R502. As a prerequisite for reliably calculating vapour pressure and phase equilibria of ternary mixtures within the relevant range of temperature and composition, VLE data of the three binary systems R32/R134a, R125/R134a and R32/R125 have been measured from −70°C up to the critical temperature. The real mixing behaviour of these binary systems is described by simple cubic equations of state, based only on precise experimental data of the critical properties and one value of the vapour pressure at T/ T c ≈ 0.7 for one mixture of nearly equimolar composition, respectively. Besides the properties of the pure substances, these data are sufficient to calculate the saturation pressure as well as the composition of the coexisting phases with rather high accuracy for both the binary and the ternary mixtures. This has been proved by comparison with experimental data for binary mixtures and for three ternary mixtures of different compositions.

A triangular lattice model for binary and ternary mixtures containing surfactants

The phase equilibria of ternary mixtures of water, oil and surfactants and binary mixtures of water and surfactants are studied using a triangular lattice-gas model that is an extension of the spin-1 Blume-Capel model with the addition of the orientational degrees of freedom for surfactants. The phase diagram of the model is investigated via Monte Carlo simulations in conjunction with the extrapolation technique of Ferrenberg and Swendsen combined with the finite-size scaling method of Lee and Kosterlitz. Five phases are found for ternary mixtures in the case of equal water and oil concentrations: a water-oil coexistence region, a lamellar phase, a liquid crystalline phase, which has the symmetry of a rhombic lattice, and an extended disordered phase, which is divided by a Lifshitz line into disordered fluid and microemulsion regions. In the limiting case of a binary mixture of water and surfactants, we found a rich phase diagram corresponding to a lamellar phase, a hexagonal phase and a disordered phase. which is again divided by a Lifshitz line into disordered fluid and structured fluid regions. The latter can be considered as the analogue of the microemulsion found for the ternary systems.

Solid-liquid phase equilibria of ternary mixtures containing polynuclear aromatic compounds

Solid-liquid phase diagrams of two ternary mixtures containing polynuclear aromatic compounds, viz., cis-decahydronaphthalene (cis-decalin)-naphthene-biphenyl and 1,2,3,4-tetrahydronaphthalene (tetralin)-biphenyl-dibenzofuran, have been measured at 298 K and 1 atm. These phase diagrams are also predicted using binary interaction parameters obtained from the regression of binary data alone using the UNIQUAC model and regular solution theory. It is observed that, by using binary parameters and UNIQUAC equations for multicomponent mixtures, one can predict the saturation curve for naphthalene within 7% and the saturation curve for biphenyl within 4% for the cis:decalin-naphthalene-biphenyl system

Vapor—liquid equilibria in ternary mixtures containing nitrogen, methane, ethane and carbondioxide at low temperatures and high pressures

Phase equilibria in ternary mixtures containing N 2, CH 4, C 2H 6 and CO 2 were studied with the purpose of supplying experimental data for testing and improving the accuracy and “truth” of theoretical models and equations of state including mixing rules. In this part T, p, x, y data are reported for CH 4C 2H 6CO 2 at T = 220.0, 233.1, 250.5 and 251.1 K and at p = 20, 30, 40 and 50 bar. The results are compared with those data calculated with generalized equations of state.