High-pressure Phase Equilibria Research Articles

High-pressure phase equilibrium and volumetric properties of pseudo-binary mixtures of stock tank oil + nitrogen/carbon dioxide up to 463K

High-pressure phase equilibrium and volumetric properties of pseudo-binary mixtures of stock tank oil + nitrogen/carbon dioxide up to 463K

High-pressure phase equilibrium data for systems involving carbon dioxide, globalide, ε-caprolactone, poly(globalide-co-ε-caprolactone) and dichloromethane

High-pressure phase equilibrium data for systems involving carbon dioxide, globalide, ε-caprolactone, poly(globalide-co-ε-caprolactone) and dichloromethane

High-pressure phase equilibrium data for the binary system carbon dioxide and ε-caprolactone

High-pressure phase equilibrium data for the binary system carbon dioxide and ε-caprolactone

High-pressure fluid-phase equilibria: Experimental methods, developments and systems investigated (2013–2016)

With this article we extend our review series on high-pressure (above 1 MPa) phase equilibrium data to articles published between 2013 and 2016, including a compilation of systems investigated, recent developments, and trends. We considered phase equilibria of vapor, liquid, and solid phases, hydrates, critical points, solubility of high-boiling substances in supercritical fluids, solubility of gases in liquids, and solubility (sorption) of volatile components in ionic liquids and in polymers. In total, we found 1400 relevant articles in the four-year period 2013–2016 which means a 40 % increase as compared to the previous review period 2009–2012. This can be explained by a more elaborated search strategy, new publication strategies of the authors, and by the ongoing scientific interest in high-pressure phase equilibria. We summarize scientific areas that drive the measurement of high-pressure phase equilibria, and we give examples of review articles, which focus on a specific topic related to experimental high-pressure phase equilibrium data.Apart from 14 systematically searched journals, we observed a tremendous increase in the number of articles found in other journals, rising from 59 articles (2009–2012) to 473 articles (2013–2016). Until the late 1990s, the average number of authors per article was approximately 3. From then on, it has been increasing almost linearly and has reached a value of 4.7 in 2016. More than one third of the articles contain data on only one system. While the average number of systems per article is close to 3, the median value is 2.For more than 4000 systems, the reference, the temperature and pressure range of the data, and the experimental method used for the measurements is given in 41 tables. Information on hydrate systems and systems containing ionic liquids are given in 6 additional tables. 47.1 % of all systems of the review period 2013–2016 contain CO2 as one of the components. Other frequently measured components are water (32 %), methane (12.3 %), nitrogen (5.1 %), propane (3.7 %), ethane (3 %), hydrogen (2.7 %), and ethanol (2.2 %). In the period 2013–2016, 18 % of the data sets involve hydrate equilibria, 15.4 % of the systems include an ionic liquid, and 7.7 % contain a refrigerant. In the period from 1988 to 2016, we observed a clear shift in the investigated systems from chlorofluorocarbon to hydrofluorocarbon and then to hydrofluoroolefin refrigerants.The number of investigations at very high temperatures and pressures has increased, since a higher number of data sets from the Earth and planetary sciences have been found and included in the period of this review. The average internal volume of all cells used for measurements in the review period is 141 mL. Many different methods for the measurements of high-pressure phase equilibrium data exist. We discuss the main advantages and challenges of the methods and give examples of their use in the period 2013–2016. The percentage of the use of synthetic methods constantly rose from 29 % in the first period (1988–1993) to 62 % in the fourth period (2005–2008). Since then, it has stayed almost constant. Analytical–isobaric–isothermal (flow) methods have been used less and less, from 22 % (1988–1993) to 5 % (2013–2016). Synthetic-nonvisual methods are used more and more often, rising from 3 % (1988–1993) to 23 % (2013–2016).

High-pressure phase equilibrium data for the ternary and quaternary systems containing carbon dioxide, globalide, ε-caprolactone dichloromethane

High-pressure phase equilibrium data for the ternary and quaternary systems containing carbon dioxide, globalide, ε-caprolactone dichloromethane

High-pressure phase equilibrium data of carbon dioxide/food-relevant systems (2011-2022): Experimental methods, multiphase behavior, thermodynamic modeling, and applications

High-pressure phase equilibrium data involving food-type substances and pure or cosolvent-modified pressurized carbon dioxide (CO2) published in the last decade are reviewed. Experimental data regarding binary, ternary, and multicomponent systems studied at 293–373 K and pressures up to 55 MPa are compiled. CO2/lipid-like substances (fatty acids, esters, triacylglycerols), essential oils, and their components are the most studied food systems, followed by systems containing biopolymers. The Vapor-Liquid Equilibrium is the most observed fluid-fluid transition at experimental conditions. The cosolvent effect of organic solvents in removing immiscibility gaps like the Vapor-Liquid-Liquid and the Liquid-Liquid boundaries, the antisolvent role of CO2 to some solutes, and its plasticizing effect on polymers and solid lipids are also highlighted in the context of solid-fluid equilibrium. The Peng and Robinson Equation of State coupled with the Van der Waals type mixing rules is still the main thermodynamic model applied for modeling phase equilibrium of these systems, despite some correlative limitations regarding multicomponent mixtures containing polar molecules. Combining classical Equations of State with the associative term and predictive models as Group Contribution methods is a reliable tool to improve the modeling of systems with complex phase behaviors. Fluid phase immiscibility regions and experimental conditions that favor the presence of a solid phase are mainly useful to set the appropriate operating point based on phase diagrams and the observed equilibria. For many applications, phase equilibrium is relevant in processing food-type substances destined for food or food-related applications and human consumption by processes employing CO2 as an extraction solvent, a fractionating, dispersant, precipitative, or atomizing (antisolvent) agent, or as a reaction medium for biocatalysis.

Martian core composition from experimental high-pressure metal-silicate phase equilibria

Martian core composition from experimental high-pressure metal-silicate phase equilibria

A new high pressure phase equilibrium cell featuring the static-combined method: Equipment commissioning and data measurement

A new equilibrium cell featuring a floating piston with an internal variable volume and phase sampling mechanism was designed and commissioned for the measurement of phase equilibrium data. The experimental technique can be extended to the static-combined method. The apparatus was tested by measuring vapor-liquid equilibrium data for the binary system of carbon dioxide + n-hexane at 313.15 K. New experimental vapor-liquid equilibrium data were also measured for the binary systems of carbon dioxide + 1,1,2,2 tetrafluoroethyl 2,2,3,3 tetrafluoropropyl ether at four temperatures, viz. (303.15, 313.15, 323.15 and 333.15) K and modeled using the Peng-Robinson Equation of State. Data close to the mixture critical points were modeled using a scaling law. The average expanded uncertainty for T, P, x1 and y1 for all systems in this work were 0.08 K, 0.002 MPa, 0.004 and 0.0007, respectively.

High-pressure phase equilibrium and volumetric properties of pseudo-binary mixtures of stock tank oil + methane up to 463K

High-pressure phase equilibrium and volumetric properties of highly asymmetric mixtures related to reservoir fluids are critical to the development of high-pressure and high-temperature (HPHT) reservoirs. However, there is a lack of the relevant data and accurate modeling tools. In this work, we prepared asymmetric pseudo-binary mixtures of methane (CH4) + stock tank oil (STO) and systematically measured their phase equilibrium and densities at temperatures from (298.15 to 463.15) K and pressures up to 140 MPa. The methane mole fraction in these mixtures range from 0.20 to 0.61 for the density measurement, and from 0.20 to 0.81 for the phase equilibrium measurement. From the experimental densities, the isothermal compressibility values, as well as the pseudo-excess volumes, were determined. Moreover, phase envelopes, relative volumes, and liquid volume fractions below the saturation point were also measured. These data are valuable for evaluating and improving thermodynamic models for HPHT reservoir fluids. The experimental results were modeled by the Soave-Redlich-Kwong (SRK) equation of state (EoS), the Peng-Robinson (PR) equation of state, their volume translated versions SRK-VT and PR-VT, and the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT). For density, SRK and PR gave large deviations of ~18% and ~8%, respectively, as compared with ~3% for PC-SAFT. Inclusion of volume translation reduced their deviations to the same level as that for PC-SAFT. For isothermal compressibility, all the models gave deviations of 20-30%, with PC-SAFT, SRK-VT and PR-VT being slightly better. The excess volumes calculated by SRK, PR and PC-SAFT were similar and close to the experimental values. The deviations in the calculated excess volumes resulted in only ~1% deviations in the calculated densities if the experimentally determined STO densities were used. It was illustrated that the small deviations could be utilized in the excess volume method to accurately estimate the high-pressure live oil densities from the high-pressure STO densities. This excess volume method gave ~1% density deviation on average for all the models, with PC-SAFT giving the smallest maximum deviation. The deviations in calculated saturation pressures were ~5% for all the models with the overall deviation for PC-SAFT being slightly smaller.

Phase Equilibrium and Density of CO2 + Acetic Acid Systems from 308.15 to 338.15 K and 15 to 45 MPa.

Using a high-pressure phase equilibrium apparatus and vibrating-tube densimeter, phase transition pressures of CO2 (1) + acetic acid (2) binary systems with x2 = 0.000, 0.107, 0.163, 0.222, and 1.000 were measured under temperatures from 308.15 to 338.15 K. Besides, the densities at the same composition and temperature under pressure from 15 to 45 MPa were also detected, and the volumes of mixing (ΔVm) were calculated. Three prediction models (SRK EOS, PC-SAFT EOS, and TS model) were introduced to predict and correlate the density of binary systems, which was found to have positive relationships with temperature and acetic acid concentration and a negative relationship with pressure. Thereinto, the variation trend of CO2 density with pressure tends to be flat under high pressure, and which of acetic acid density increased linearly with pressure. ΔVm are negative, and their absolute value increases with the increase of temperature and the decrease of pressure. The work herein could provide a theoretical guide and basic data for supercritical CO2 extraction technology and CO2 application in oil field development.

Experimental high-pressure phase equilibria of carbon dioxide/n-alkanes mixtures and model-parameters for solid-phase obtained from DSC thermograms

We provide high-pressure experimental phase equilibrium data for systems containing mixtures formed by CO2 and mixtures of n-alkanes (n-C10H22/n-C20H42, n-C10H22/n-C24H50, n-C10H22/n-C20H42/n-C24H50) with CO2 weight fractions of 55%, 65% and 75%, temperature ranging from 273 K to 363 K and pressures up to 55 MPa. The measured equilibrium data include vapor-liquid (VL), solid-liquid (SL), and solid-liquid-vapor (SVL) phase transitions. Additionally, calorimetric (DSC) measurements were carried out at atmospheric pressure for mixtures of n-C10H22 (solvent), n-C16H34, n-C20H42, and n-C24H50, with the temperature range from 253 K to 333 K. To describe the phase-equilibrium diagrams, the solid phases were modeling using the multiple-solid solutions approach, which employs the modified UNIQUAC equation to calculate the activity coefficients. The UNIQUAC-energy interaction parameter λij and the Poynting correction factor were used to take into account the n-alkane/n-alkane interactions and pressure effect in the solid-liquid equilibria. We used the Peng-Robinson equation of state to describe the liquid and vapor phases. The phase equilibrium predictive calculations were in good agreement with the measured phase-transition data considering the experimental uncertainty.

Determination of high-pressure phase equilibrium data of systems containing supercritical carbon dioxide and globalide

The growing interest in producing biocompatible polymers, free of any kind of toxic residues, increasingly encourages the development of researches on clean processes. The use of supercritical carbon dioxide (scCO2), replacing organic solvents, has shown to be a green alternative to traditional polymerization processes. In order to establish better conditions for polymerization reactions using the monomer globalide, the high-pressure phase behavior of systems containing carbon dioxide and globalide were studied. The experiments were performed by static-synthetic method for systems with mass fractions of CO2 ranging from 0.3542 to 0.9480 at temperatures of 313.15, 323.15, 333.15 and 343.15 K. Transitions of vapor-liquid type with bubble point (VLE -BP) and dew point (VLE-DP) were observed between 8.96 and 25.55 MPa. The experimental results were fit using the Peng–Robinson equation of state with the conventional quadratic mixing rule (PR-vdW2), providing a satisfactory representation of the experimental data.

High-Pressure Phase Equilibrium Studies of Multicomponent (Alcohol-Water-Ionic Liquid-CO2) Systems

Selective water (by-product) separation from reaction mixtures stands as an important process intensification strategy for equilibrium-limited reactions. In this work, the possibility of using a high-pressure biphasic reaction media composed of a hydrophobic ionic liquid, 1-hexy-3-methylimidazolium tetracyanoborate, and carbon dioxide was explored for levulinic acid production from 1,4-butanediol. Vapour-liquid equilibrium measurements were performed for the binary (diol+CO2), ternary (diol+CO2+IL), and quaternary systems (diol+CO2+IL+water), at 313.2 K and pressures up to 18 MPa. The static analytical method was used in a high-pressure phase equilibrium apparatus equipped with a visual sapphire cell. The capability of the quaternary system to perform physical water separation is discussed in this paper.

Measurement, correlation and modelling of high-pressure phase equilibrium of PLGA solutions in CO2

Poly (lactic-co-glycolic acid) (PLGA) is a copolymer used as drug carrier in controlled release systems as microparticles or scaffolds. Foamed structures are industrially obtained by injecting gas at temperatures above the melting point of the polymer that may promote PLGA degradation. High temperatures are avoidable in this foaming process if a polymer dissolution is used. Ethyl acetate and ethyl lactate are suitable solvents for the PLGA since the polymer is easily solubilised, is environmentally friendly and highly recommendable for medical purposes. CO2 is proposed as antisolvent because is environmentally benign, non-flammable and non-toxic. The knowledge of the solubility of these solvents in CO2 is essential to find the most appropriate working conditions for the foaming process. In this work, the solubility of ethyl acetate and ethyl lactate in CO2 in the presence of different initial concentrations of PLGA has been studied at 298.15 K and at pressures up to 150 bar using a high-pressure variable volume view cell.

New experimental VLE data for the binary mixture of carbon dioxide + perfluorohexane (CO2 + C6F14) from 273 K to 333 K

Mixtures of carbon dioxide and perfluorocarbons are more frequently used in different fields: in energy conversion systems, in the electronic industry, in chemical plants and for medical applications. Among all perfluorocarbons, perfluorohexane has interesting properties (e.g. high thermal stability and high carbon dioxide solubility) to be used in mixture, as a working fluid in power and refrigeration cycles. The study of these systems relies on the availability of accurate thermodynamic models of the fluid mixture, which usually require to be calibrated on experimental data. Experimental data on the carbon dioxide and perfluorohexane mixture are scarcely available in literature and limited to a very narrow temperature range. This work aims to enrich the available literature data on VLE measurements of carbon dioxide and perfluorohexane mixture. On the basis of the implemented static-analytical method, high-pressure phase equilibrium data have been collected. Isothermal measurements have been performed within the temperature range of 273 K–333 K and at pressures up to 8.5 MPa. Particular attention to calibration procedures of the measuring devices (temperature and pressure probes and gas chromatograph) and to uncertainty calculation has been devoted. Finally, measurements show a good agreement with the data available in literature.

Bulk moduli and high pressure crystal structure of U3Si2

Bulk moduli are important parameters to assess the mechanical performance of materials including nuclear fuels. However, little experimental data exist for U3Si2, a potential accident-tolerant nuclear fuel, whose bulk modulus has only been measured by resonant ultrasonic spectroscopy (RUS). In addition, the knowledge for high-pressure structural behavior and phase equilibrium of U3Si2 is largely lacking. Here we studied pressure dependence of the crystal structure of U3Si2 using high-energy synchrotron X-ray diffraction coupled with Rietveld analysis. The pressurization was achieved using a diamond anvil cell (DAC) which provides quasi-hydrostatic pressures up to 37.6 GPa. Crystal structural variation and equations of state of U3Si2 were obtained, and its bulk modulus, a- and c-axial moduli were derived to be 107.11 ± 5.65 GPa, 82.87 ± 4.78 GPa and 194.52 ± 12.03 GPa, respectively. The determined elastic parameters are compared with those obtained by RUS and nanoindentation.

New vapour-liquid equilibrium data on the ternary system carbon dioxide – methanol – dimethyl sulphoxide

Knowing high-pressure phase equilibrium is essential for the numerous applications of organic solvent-entrained supercritical carbon dioxide, as well for extraction as for antisolvent procedures. Phase equilibrium measurements on the carbon dioxide – methanol – dimethyl sulphoxide mixture are presented in the range of 308 K–323 K and 7.5 to approx. 11.5 MPa. Composition (mole fraction) was varied for each component in the ranges xCO2:0.75−0.88; xMeOH:0.042−0.21; and xDMSO:0.025−0.12. Measurements were done using a static synthetic method based on the observations of cloud points and redissolution points. Measurement results were well approximated by the Peng-Robinson equation of state.

A novel technique based in a cylindrical microwave resonator for high pressure phase equilibrium determination

The development of a novel technique based on a cylindrical microwave resonator for high pressure phase equilibrium determination is described. Electric permittivity or dielectric constant is a physical property that depends on temperature and pressure ε(p,T). Based on this property, a measuring technique consisting of a cylindrical resonant cavity that works in the microwave spectrum has been developed. Equilibrium data of fluid mixtures are measured at high pressure using a synthetic method, where phase transition is determined under isothermal conditions due to the change of the dielectric constant. This technique may be a more accurate alternative to conventional visual synthetic methods. The technique was validated measuring pure CO2, and phase behaviour was then determined for two binary mixtures {CO2 (0.6) + CH4 (0.4)} and {CO2 (0.4) + CH4 (0.6)}, results for which are presented. These systems are interesting for the study of biogas-like mixtures. In addition, data were compared with the equation of state used for natural gas GERG-2008, and also, they were modelled using Peng-Robinson equation of state and Wong-Sandler mixing rules, which are widely employed in chemical industries and which give good results.

High Pressure Phase Equilibrium Data for the Ternary System Containing Carbon Dioxide, Dichloromethane, and ε-Caprolactone

This work reports experimental phase equilibrium data for the ternary system involving e-caprolactone, carbon dioxide, and dichloromethane. Such data provide fundamental information to conduct poly...

VLE measurements and modelling for the binary systems of (CF4 + C6F14) and (CF4+ C8F18)

Isothermal phase equilibrium data were measured for the binary systems of tetrafluoromethane with either perfluorohexane or perfluorooctane to investigate the effect of carbon chain length of the solvent with regards to the solubility of tetrafluoromethane. Both the “static-analytic” and the “static-synthetic” methods were utilized to measure the high-pressure phase equilibrium data. Isothermal measurements were performed within the temperature range of (283.15–303.15) K and at pressures up to 11 MPa. Vapour pressure data for perfluorohexane and perfluorooctane were measured within the temperature range of (283.15–323.15) K. Additionally, isothermal vapour-liquid equilibrium data were measured for the binary system of carbon dioxide + n-hexane at 313.15 K; the data were utilized to validate the experimental method. The experimental data were modeled using the Peng-Robinson equation of state with the Wong-Sandler mixing rule and Non-Random Two-Liquid excess Gibbs energy model. The model provides a satisfactory representation of the experimental data within the measured temperature range.