Liquid Equilibrium Measurements Research Articles

Water–Ionic Liquid Working Fluids in Absorption Cycles: Fluid Screening, Vapor–Liquid Equilibrium Measurements and Modeling, and Performance Evaluation

Water–Ionic Liquid Working Fluids in Absorption Cycles: Fluid Screening, Vapor–Liquid Equilibrium Measurements and Modeling, and Performance Evaluation

Isothermal vapor–liquid equilibria of binary mixtures containing (methanol, or propan-1-ol, or water, or acetonitrile) and 1-ethyl-3-methylimidazolium thiocynate ionic liquid: Measurements and modeling

Ionic liquid vapor–liquid equilibrium (VLE) measurements were performed on binary systems for1-ethyl-3-methylimidazolium thiocynate [EMIM][SCN] (2) + {methanol, or propan-1-ol or water or acetonitrile}(1) at range temperatures between 273.15 and 363.15 K. Experiments were undertaken at pressures between 15 Pa and 255 kPa using a static device. The reported data were successfully correlated by means of two models, namely NRTL or COSMO-RS, and the PC-SAFT equation of state. While results obtained in this study indicate that the phase behavior of systems involving the ionic liquid and alcohols, water or acetonitrile can be accurately described by these three models, it was found that experimental data may be represented with higher accuracy with PC-SAFT than NRTL and COSMO-RS models.

Isothermal (vapor ＋ liquid) equilibrium measurements and correlation of the binary mixture 3,3,3-trifluoropropene (R1243zf) ＋ isobutane (R600a) at temperatures from [formula omitted] to [formula omitted] K

The restrictions set by the F-gas Regulation and the Kigali Amendment to the Montreal Protocol have pushed an extensive research into alternatives for fluorinated greenhouse gases in air conditioning and refrigeration. Hydrofluoroolefins (HFOs) are emerging as promising substitutes for hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) in HVAC and refrigeration. Amongst these, R1243zf raised interests as low-GWP substitutes for R134a. The pursuit of low GWP refrigerants has also led to the examination of hydrocarbons (HCs), like propane (R290) and isobutane (R600a), due to their efficiency, low charge, and affordability, despite their flammability. The mixtures of R1243zf and isobutane could be of interest for medium temperature heat pump applications. Moreover, blending HFOs with HCs usually leads to azeotropic mixtures. While HCs benefit of a wide range of data and reliable Equations of State (EoS), HFOs, and in particular their mixtures, lack comprehensive information. This study reports vapor–liquid equilibrium (VLE) measurements for the 3,3,3-trifluoropropene (R1243zf) + isobutane (R600a) binary system in the temperature range between 283.15 K and 323.15 K. The measurements have been carried out by means of a vapor-recirculation apparatus combined with gas-chromatographic analysis. This work reports 53 experimental data with an expanded uncertainty (k=2) of 0.003 mol mol−1. The reported data, along with the data available in the literature, have been used to developed two new mixture models based on the Helmholtz free energy EoS, both leading to a significant improvement in the VLE prediction, with RMSE values lower than 0.005 mol mol−1 for both the liquid and the vapor phase composition.

A new method to combine high-pressure vapor–liquid equilibrium and thermophysical property measurements for low-volatility liquids and a gas

Vapor-liquid equilibria measurements involving liquids with low volatility, such as many types of lubricants, ionic liquids, and various solvents are essential for process research and development in a wide variety of fields. State–of–the–art methods to measure these phase equilibria, e.g. thermogravimetric analysis or equilibrium cells, generally cannot be combined with instruments measuring thermophysical properties, e.g. density, transport properties, spectroscopic properties, etc. A novel approach was developed to measure simultaneously vapor–liquid equilibrium and thermophysical properties involving a single gas dissolved in one or more low-volatility liquids. The method is based upon a mass balance measuring liquid phase density, total masses in the system, and volumes. The governing equations of the novel approach are derived, and a detailed uncertainty analysis is presented. As an example, the solubility, density, and viscosity are measured with the new apparatus for a system of a non-volatile ionic liquid solvent saturated with the compressed hydrofluorocarbon gas, pentafluoroethane (R-125), at 25 °C and 75 °C and pressures to ∼ 3.1 MPa. The solubility data are validated by comparison to previously published literature data using a high precision gravimetric microbalance. The combination of vapor–liquid equilibria and thermophysical properties in a single experiment can significantly accelerate scientific and engineering studies.

Vapor–Liquid Equilibrium and PVTx Property Measurements of HFO1123 + CF3I and HFC125 + CF3I

Vapor–Liquid Equilibrium and PVTx Property Measurements of HFO1123 + CF3I and HFC125 + CF3I

Study of Methanol Extraction from Saturated Alkanes: Solvent Screening, Liquid–Liquid Equilibrium Measurement, and Thermodynamic Simulation

Study of Methanol Extraction from Saturated Alkanes: Solvent Screening, Liquid–Liquid Equilibrium Measurement, and Thermodynamic Simulation

Isothermal (Vapour + Liquid) Equilibrium Measurements and Correlation of the Binary Mixture {3,3,3-Trifluoropropene (HFO-1243zf) + 2,3,3,3-tetrafluoropropene (HFO-1234yf)} at Temperatures from 283.15 K to 323.15 K

The many constrains introduced by the F-gas Regulation and the Kigali Amendment to the Montreal Protocol have resulted in an intense search for alternatives to fluorinated greenhouses gases for air conditioning and refrigeration purposes (Mota-Babiloni A, Makhnatch P, in Int J Refrig 127:101–110, 2021). With respect to the urge of new low-GWP and low-ODP refrigerants, blends composed of hydrofluoroolefins (HFO) are considered promising possible substitutes to hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons (HCFCs) for HVAC&R applications (Sovacool et al., in Renew Sustain Energy Rev 141:110759), but thermophysical properties data for these blends are still scarce (Bell et al., in: J Chem Eng Data, 2021). In the present study, the vapor–liquid equilibrium (VLE) for the binary system (HFO-1243zf + HFO-1234yf), for which just one set of data on the VLE is available to date in literature, has been experimentally studied by means of a vapor recirculation apparatus. The measurements have been performed at isothermal conditions in the range of temperatures between 283.15 K and 323.15 K, while the composition of both the phases in equilibrium has been measured by gas-chromatographic analysis. The experimental VLE data have been correlated by two different equations of state (EoS): the Peng-Robinson (PR) EoS combined with Mathias–Copeman (MC) alpha function and van der Waals (vdW) mixing rules, and the Helmoltz EoS with dedicated binary interaction parameters. Correlated results showed a good agreement with the experimental data for the binary system.

Density, Excess Molar Volume and Vapor–Liquid Equilibrium Measurements at 101.3 kPa for Binary Mixtures Containing Ethyl Acetate and a Branched Alkane: Experimental Data and Modeling

Vapor–liquid equilibrium (VLE) and density data for binary systems of branched alkanes + ethyl acetate are scarce in the literature. In this study, the binary mixtures 3-methylpentane + ethyl acetate and 2,3-dimethylbutane + ethyl acetate were investigated. Density measurements at atmospheric pressure were performed using a vibrating tube density meter at 293.15, 298.15 and 303.15 K. Large and positive excess molar volumes were calculated and correlated using a Redlich–Kister-type equation. Isobaric VLE data at 101.3 kPa were obtained using a Gillespie-type recirculation ebulliometer. Equilibrium compositions were determined indirectly from density measurements. The experimental data were checked for consistency by means of the Fredenslund test and the Wisniak (L-W) test and were then successfully correlated using the NRTL model. The newly studied binary systems display high deviations from ideality and minimum boiling azeotropes, the coordinates of which are reported in this work.

Separation of Azeotropic Mixtures of Ethyl Acetate + Methylcyclohexane: Vapor–Liquid Equilibrium Measurements

It is a challenge to separate ethyl acetate from methylcyclohexane because of the azeotropic phenomenon. To provide a basis for the design of the separation process, the isobaric vapor–liquid equilibria for an ethyl acetate + methylcyclohexane binary system were measured at 101.3 and 20.0 kPa using a modified Othmer-type still. The results show that ethyl acetate and methylcyclohexane form a miscible azeotropic mixture with minimum boiling temperature (349.99 K at 101.3 kPa), of which the composition varies slightly with decreasing pressure (≤101.3 kPa). It implies that ethyl acetate cannot be separated from methylcyclohexane by pressure-swing distillation. The azeotropy of ethyl acetate and methylcyclohexane disappears in the presence of decane (∼0.5 mole fraction), which means that ethyl acetate can be separated from methylcyclohexane by extractive distillation with decane as an entrainer.

The Effect of Sulfate Electrolytes on the Liquid–Liquid Equilibrium of 2-MTHF/Water/5-HMF: Experimental Study and Thermodynamic Modeling

We investigate the influence of sulfate salts and sulfuric acid on the equilibrium behavior of 2-methyltetrahydrofuran (2-MTHF)/H2O/5-hydroxymethylfurfural (5-HMF). Liquid–liquid equilibrium measurements are performed at atmospheric pressure and in a temperature range of T = (293–333) K. The compositions of the aqueous and organic phases, together with the dissociation state of the sulfate species, are determined with infrared spectroscopy and Indirect Hard Modeling. We show that the addition of the salts Na2SO4 and Li2SO4 results in salting out of 2-MTHF and 5-HMF from the aqueous phase. With increasing temperature, this effect gets less pronounced. In contrast, the addition of H2SO4 does not result in any salting-out behavior. The investigation of the dissociation states shows that H2SO4 dissociates to HSO4– while Na2SO4 and Li2SO4 dissociate completely to SO42–. Parameter regression is performed to model the liquid–liquid equilibrium with the electrolyte perturbed-chain statistical associating fluid theory (ePC-SAFT) equation of state. For the analyzed salts, Na2SO4 and Li2SO4, the performed parameter regression accurately predicts the measurement results. Still, we observe slight deviations between measured values and modeling when predicting the liquid–liquid equilibrium and the liquid density in the presence of sulfuric acid.

Vapor–Liquid Equilibrium Measurements for Aqueous Mixtures of NH3+ MDEA + CO2and KOH + MDEA

Isothermal vapor–liquid equilibrium measurements were performed for aqueous solutions containing N-methyl diethanolamine (MDEA), MDEA + ammonia (NH3), MDEA + potassium hydroxide (KOH), MDEA + carbon dioxide (CO2), NH3 + CO2, and MDEA + NH3 + CO2. The experiments were carried out between 310 and 390 K and 0.07 and 34 bar using a static synthetic apparatus. Overall, 202 data points are reported in terms of total volume, total number of moles, temperature, and pressure. The experimental results for MDEA(aq), NH3(aq) + CO2(aq), and MDEA(aq) + CO2(aq) are in good agreement with the calculations done using the Extended UNIQUAC model within the studied range. The data presented in this work are also comparable to previously published measurements. This work reports for the first time VLE measurements for aqueous mixtures of MDEA + NH3 and MDEA + KOH. These data suggest that the interactions between MDEA(aq) and NH3(aq) or K+(aq) ions have a minor effect on the equilibrium pressures. Consequently, other physical properties are needed to describe the thermodynamic state of these systems, such as heat capacity, heat of dilution, and other phase equilibrium measurements. The isothermal VLE measurements for solutions containing NH3(aq) showed a pressure minimum that was confirmed by model estimates and by other works done in similar conditions. As a consequence, it is not possible to estimate the partial pressure of CO2 based on the difference between the pressure at equilibrium conditions and the partial pressure of the lean solvent. This paper demonstrates that this common approach to determining the partial pressure of gases may introduce a bias in these values. The dissolution of CO2 into MDEA(aq) + NH3(aq) mixtures changes the speciation of the system, leading to an increase in the concentration of their protonated species (MDEAH+(aq) and NH4+(aq), respectively). For this reason, the interaction between these charged species must be determined in order to perform reliable phase equilibrium calculations. Ultimately, the measurements reported in this work can be used for thermodynamic modeling of CO2 capture solvents to ensure accurate results in process simulation.

Liquid–liquid equilibrium measurements and computational study of salt–polymer aqueous two phase system for extraction of analgesic drugs

In recent decades, aqueous two phase systems have gained a lot of attention for extraction of different materials. In this work, an aqueous two phase system was made by polyethylene glycol 600 and potassium hydroxide and phase diagram were determined for this system. The experimental binodal data were described using two empirical nonlinear three parameter expressions developed by Merchuk and Zafarani-Moattar. The consistency of the experimental tie-line data was determined by utilizing the Othmer-Tobias, Bancraft, and Setschenow correlations. Also, the extraction of two analgesic drugs, namely ibuprofen and acetaminophen were investigated by the mentioned ATPS. For this purpose, partition coefficients and extraction efficiencies of each drug were calculated. The trend of extraction efficiencies indicated that the responsibility of extraction of the mentioned drugs into the polymer-rich top phase is related to their hydrophobicity. The Diamond-Hsu equation and its modified version were used to correlate the drugs experimental partition coefficients. Furthermore, the interaction of mentioned drugs with polyethylene glycol was investigated employing quantum computing techniques based upon density functional theory (DFT). These results were in good agreement with the trend of extraction efficiencies of studied drugs.

Entrainers Selection and Vapor–Liquid Equilibrium Measurements for Separation of p-Xylene from Ethylbenzene at 101.3 kPa

Entrainers Selection and Vapor–Liquid Equilibrium Measurements for Separation of p-Xylene from Ethylbenzene at 101.3 kPa

Experimental characterisation of CO2 + C6F6 mixture: Thermal stability and vapour liquid equilibrium test for its application in transcritical power cycle

• Analysis of CO 2 blend as working fluid in transcritical cycle for CSP application. • Experimental vapour liquid equilibrium measurements. • Equation of state calibration with VLE data. • Maximum operating temperature identified through thermal stability test. • Preliminary thermodynamic assessment of the power cycle. Nowadays supercritical CO 2 cycles are considered as a promising alternative to the traditional steam cycle for the power block in CSP plants with the aim of enhancing the system efficiency and reducing costs. This work deals with the experimental characterisation of a CO 2 blend as working fluid in transcritical cycle: the addition of C 6 F 6 as a dopant increases the fluid critical temperature allowing for a condensing cycle in hot environment with ambient temperature higher than 40 °C. The potential benefits on adopting this mixture passes through thermal stability test for identifying its maximum operating temperature and Vapour Liquid Equilibrium measurements for tuning the Equations of State, thus having a good prediction of the thermodynamic properties. The static method with thermal stress test at different operating temperatures shows that the mixture can withstand to about 600 °C in an Inconel 625 vessel. Furthermore, the standard Peng-Robinson with the optimised binary interaction parameter is selected for a preliminary thermodynamic assessment of the power cycle. An efficiency of 41.9% is found for an optimum mixture composition with a CO 2 molar content of 84% considering a turbine inlet pressure of 250 bar and a maximum and minimum cycle temperature of 550 °C and 51 °C respectively.

Isobaric Vapor–Liquid Equilibria Measurements and Thermodynamic Modeling for the Systems Containing 2-Butanone, C3 Alcohols, and C4 Esters: Part I─Binary Mixtures

Isobaric Vapor–Liquid Equilibria Measurements and Thermodynamic Modeling for the Systems Containing 2-Butanone, C₃ Alcohols, and C₄ Esters: Part I─Binary Mixtures

Extension of the AIOMFAC model by iodine and carbonate species: applications for aerosol acidity and cloud droplet activation

Abstract. Iodine and carbonate species are important components in marine and dust aerosols, respectively. The non-ideal interactions between these species and other inorganic and organic compounds within aqueous particle phases affect hygroscopicity, acidity, and gas–particle partitioning of semivolatile components. In this work, we present an extended version of the Aerosol Inorganic–Organic Mixtures Functional groups Activity Coefficients (AIOMFAC) model by incorporating the ions I−, IO3-, HCO3-, CO32-, OH−, and CO2(aq) as new species. First, AIOMFAC ion interaction parameters for aqueous solutions were determined based on available thermodynamic data, such as water activity, mean molal activity coefficients, solubility, and vapor–liquid equilibrium measurements. Second, the interaction parameters for the new ions and various organic functional groups were optimized based on experimental data or, where data are scarce, alternative estimation methods such as multiple linear regression or a simple substitution by analogy approach. Additional bulk water activity and electrodynamic balance measurements were carried out to augment the database for the AIOMFAC parameter fit. While not optimal, we show that the use of alternative parameter estimation methods enables physically sound predictions and offers the benefit of a more broadly applicable model. Our implementation of the aqueous carbonate–bicarbonate–CO2(aq) system accounts for the associated temperature-dependent dissociation equilibria explicitly and enables closed- or open-system computations with respect to carbon dioxide equilibration with the gas phase. We discuss different numerical approaches for solving the coupled equilibrium conditions and highlight critical considerations when extremely acidic or basic mixtures are encountered. The fitted AIOMFAC model performance for inorganic aqueous systems is considered excellent over the whole range of mixture compositions where reference data are available. Moreover, the model provides physically meaningful predictions of water activity under highly concentrated conditions. For organic–inorganic mixtures involving new species, the model–measurement agreement is found to be good in most cases, especially at equilibrium relative humidities above ∼ 70 %; reasons for deviations are discussed. Several applications of the extended model are shown and discussed, including the effects of ignoring the auto-dissociation of water in carbonate systems, the effects of mixing bisulfate and bicarbonate compounds in closed- or open-system scenarios on pH and solution speciation, and the prediction of critical cloud condensation nucleus activation of NaI or Na2CO3 particles mixed with suberic acid.

Isothermal Vapor–Liquid Equilibrium (P–T–x–y) Measurements and Modeling of Propan-2-ol +n-Octane/n-Decane in the Range ofT= 313.2–353.2 K

Isothermal Vapor–Liquid Equilibrium (<i>P</i>–<i>T</i>–<i>x</i>–<i>y</i>) Measurements and Modeling of Propan-2-ol +<i>n</i>-Octane/<i>n</i>-Decane in the Range of<i>T</i>= 313.2–353.2 K

Separation of the Azeotropic Mixture Methanol and Toluene Using Extractive Distillation: Entrainer Determination, Vapor-Liquid Equilibrium Measurement, and Modeling.

For separating the azeotropic mixture methanol and toluene, an extractive distillation is applied with butyl propanoate, triethylamine, and butyl butanoate as the extractive solvents, which were screened by relative volatility, selectivity, and the x–y curve. The vapor–liquid equilibrium data of the binary and ternary systems for (toluene + butyl propanoate), (toluene + triethylamine), (toluene + butyl butanoate), and (methanol + toluene + butyl butanoate) were determined. The reliability for the experimental vapor–liquid equilibrium (VLE) data was assessed with the van Ness method. The measured data was fitted by the UNIQUAC, Wilson, and NRTL models, and the correlated results were consistent with the determined VLE data. In addition, the COSMO-UNIFAC model was used to predict the VLE data for comparison.

Phase Equilibria of Aqueous Two-Phase Systems of PEG with Sulfate Salt: Effects of pH, Temperature, Type of Cation, and Polymer Molecular Weight

The present work reports the liquid–liquid equilibrium (LLE) measurements and the construction of binodal curves for polyethylene glycols (PEG) + zinc sulfate/ammonium sulfate + water at three different temperatures (298.15, 303.15, and 308.15 K) and pH values (3.00, 4.70, and 5.21). PEGs with different molecular weights of 2000 g·mol–1 (PEG 2000), 3000 g·mol–1 (PEG 3000), and 8000 g·mol–1 (PEG 8000) were chosen for this study. The phase composition was obtained by measuring the refractive index (nD) and density (ρ) and was further used to obtain the tie-line length (TLL) and the slope of tie-line (STL). The tie-lines are reported at different polymer lengths, pH values, and temperatures. The values of the effective excluded volume (EEV) were employed to analyze the effect of the parameters on the binodal curves. Moreover, the impact of those parameters on the TLL and STL and plait point are discussed and compared with the results of the literature. Furthermore, the binodal curves data and the tie-lines’ ends were fitted using some semiempirical equations with satisfactory results. Finally, the UNIFAC is used to calculate the LLE data of the above system and the adjusted binary group interaction parameters of the model were reported.

Isobaric Vapor–Liquid Equilibrium Measurements of Binary Systems of Dimethyl Carbonate with Dimethyl Sulfoxide, Anisole, and Diethyl Oxalate at 101.3 kPa

In this work, three entrainers were selected to separate the azeotrope of dimethyl carbonate (DMC) and methanol, which were dimethyl sulfoxide, anisole, and diethyl oxalate. The vapor–liquid equilibrium (VLE) data of four binary systems (DMC + dimethyl sulfoxide, DMC + anisole, DMC + diethyl oxalate, and methanol + diethyl oxalate) were measured using a modified Rose-type circulating still at 101.3 kPa. The Van Ness point-to-point test and infinite dilution test were used to test the thermodynamic consistency of the experimental VLE data. The nonrandom two-liquid, universal quasi-chemical, and Wilson models were used to correlate the measured VLE data. The binary interaction parameters of the three models were regressed.