Variable-volume Cell Research Articles

Density measurements of homogeneous phase fluid mixtures comprising CO2/methanol and CO2/ethanol binary systems and correlation with equations of state

Equations of state (EoS) are powerful tools for estimating a wide variety of physical properties. However, the applicability of parameter sets derived from specific physical properties for the correlation and estimation of various other physical properties has received limited attention. Additionally, the estimation of physical properties using EoS is anticipated to be affected by the association of molecules. The densities of homogeneous phase fluid mixtures comprising carbon dioxide (CO2)/methanol (MeOH) and CO2/ethanol (EtOH) binary systems were measured in the current study using a high-pressure vibration-type density meter equipped with a circulation pump and a variable-volume viewing cell. Homogeneity was ensured by observing the fluid through the viewing window of the variable volume cell. The measurements were carried out at a temperature range of 313–353 K, the CO2 mole-fraction range of 0–80 mol%, and at pressures up to 20 MPa. Subsequently, the as-obtained experimental data were correlated with two EoSs, viz. Sanchez-Lacombe (SL) EoS and Perturbed Chain statistical associating fluid theory (PC-SAFT) EoS. The density correlations between SL and PC-SAFT EoS were almost identical in accuracy. Additionally, the association between CO2 and alcohols in PC-SAFT EoS had no discernible effect on the reliability of the density correlations. The vapor liquid equilibria (VLE) of the CO2/MeOH and CO2/EtOH mixtures were further estimated using parameter sets determined from the density measurements. Both the EoSs demonstrated comparable estimation accuracy; however, the pressure was estimated primarily near the critical region of the mixture, which yielded a lower estimation accuracy. Additionally, the densities of the binary systems were determined using characteristic parameters derived from the VLE correlations. Of the EoSs, the PC-SAFT EoS yielded a good correlation of the VLE, including the region near the mixture's critical region, while taking the association between CO2 and alcohols into consideration. Although few of the correlations were observed to be inferior, the density of the homogeneous fluid mixture was accurately estimated using the two EoSs, with the parameters obtained from the VLE correlations. The findings of the study thus suggest that in order to estimate the density and VLE using EoS-shared parameters, the parameter sets must first be determined using a VLE that exhibits a wide range of conditions affected by the system's associations.

Experimental investigation of the CO2+SiCl4 mixture as innovative working fluid for power cycles: Bubble points and liquid density measurements

Supercritical CO2 is recognized as a promising working fluid for next-generation of high temperature power cycles. Nevertheless, the use of CO2 mixtures with heavier dopants is emerging as a promising alternative to supercritical CO2 cycles in the recent years for air-cooled systems in hot environments. Accordingly, this work presents an experimental campaign to assess the thermodynamic behaviour of the CO2+SiCl4 mixture to be used as working fluid for high-temperature applications, conducted in the laboratories of CTP Mines Paris PSL. At first, bubble conditions of the mixture are measured in a variable volume cell (PVT technique), then liquid densities are measured with a vibrating tube densimeter, for molar composition in the range between 70 % and 90 % of CO2. The Peng Robinson EoS was fine-tuned on the bubble points obtained, resulting in a satisfactory accuracy level. Finally, a non-conventional methodology has been developed to measure bubble points with the vibrating tube densimeter, whose results are consistent with the VLE data obtained with the standard PVT technique. Thermodynamic analysis in next-generation concentrated solar power plant, at 700 °C turbine inlet, confirms the mixture overcomes 50 % thermal efficiency, providing +4.2 % net electrical output over pure supercritical CO2 at equal thermal power from the solar field.

Enhancing electrochemomechanics: How stack pressure regulation affects all-solid-state batteries

Stack pressure application in solid-state batteries (SSBs) is crucial for achieving high-energy density by promoting interfacial contact. Fluctuations in stack pressure at the MPa-scale can result in mechanical fatigue, leading to the degradation of materials within a fixed-volume cell casing. Thus, it is essential to regulate these stack pressure variations during cycling. In this study, we successfully stabilize the evolution of stack pressure at the hundred kPa-scale by incorporating compression springs into the conventional SSB assembly. This kPa-level stabilization is achieved by converting elastic potential energy into spring deformation. We investigate these mechanical responses by correlating them with stack pressure and cell thickness measurements in a variable volume cell. Furthermore, accommodating volume changes results in more than 98 % retention of the highest stack pressure retention. These findings can significantly contribute to advancements in cell assembly processes critical for scaling up SSB modules.

Experimental data and thermodynamic modeling of the CO2 + Acetone + Efavirenz system at high pressures

It is important to understand the fluid phase behavior of the systems containing CO2, acetone, and Efavirenz for processes that use supercritical fluids to produce micro and/or nanoparticles for drug encapsulation. Thus, the purpose of this work is to measure experimentally data on the phase transitions of CO2 + Efavirenz and CO2 + acetone + Efavirenz systems using the visual static synthetic method and a variable-volume cell integrated into the experimental equipment. The experimental settings for the binary system were: pressures up to 16 MPa, temperatures of 333.15, 338.15, and 343.15 K, and the global Efavirenz mole fraction from 4 × 10−5 up to 15 × 10−5. The experimental settings for the ternary system were: pressure up to 10 MPa, temperatures from 303.15 to 333.15 K, and the global CO2 mole fraction from 0.2 up to 0.9. For the binary systems, the observed phase transitions are solid–fluid transitions; for the ternary systems, the observed phase transitions are bubble point (BP) transitions. Thermodynamic simulations using the Group Contribution Volume-Translated Peng-Robinson (GC-VT-PR) and Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) equations of state (EoS) demonstrated a striking correlation with experimental data. The relative deviations from pressure and temperature corroborate the efficiency of the thermodynamic models used in this work.

Minimum miscibility pressure of CO2 and oil evaluated using MRI and NMR measurements

The minimum miscibility pressure (MMP) between CO2 and crude oil is a critical parameter for CO2 enhanced oil recovery (EOR). Whilst different methodologies have been employed to determine MMP, these methods are either time-consuming or unable to be executed in the actual rock core samples from the relevant reservoir and as such, do not directly consider any accompanying kinetic effects. Here we consider a range of nuclear magnetic resonance (NMR) measurement techniques performed on a benchtop NMR apparatus in terms of their ability to estimate MMP; specifically 1D imaging, self-diffusion measurements and T1/T2 relaxation measurements. Such MMP measurements were performed on two model oils (decane and hexadecane), allowing for validation against comparable MMP literature data, and a local crude oil sample – in this case the results were compared against a PVT measurement performed using a high-pressure variable volume cell (VVC). Reasonably good agreement with these alternative sources of MMP data were realized via NMR measurements of self-diffusion; these provided consistent estimates of MMP for a wider range of oils when compared to 1D imaging and NMR relaxation measurements. NMR T2 measurements however performed equivalently to self-diffusion measurements for higher viscosity fluids based on the limited number of samples studied; such measurements require much simpler NMR hardware and are more readily accessible in both the laboratory and in the field.

Critical properties and vapor-liquid equilibrium of two near-azeotropic mixtures containing HFOs

This work studies two binary mixtures of R1243zf + R1234yf and R1243zf + R245cb which can be possibly used as a long-term alternative refrigerant for heat pumps. We present critical property (critical temperature, pressure, density) and vapor liquid equilibrium (VLE) of R1243zf + R1234yf and R1243zf + R245cb two binaries. The maximum extended uncertainties (k=2) are estimated as U(T) = 0.21 K, U(p) = 0.048 MPa, and U(ρ) = 6.4 kg/m3 for critical property measurement, and U(T) = 0.06 K and U(p) = 0.015 MPa for bubble point measurement. The uncertainty of liquid-phase mole fraction is estimated less than 1.8 × 10−4. The critical property is investigated by a novel method that determines the critical point via modeling vapor-liquid coexistence points to the combined equations of the scaling law and rectilinear diameters law. The VLE of R1243zf + R1234yf and R1243zf + R245cb binary mixtures in the range of 293.45 to 353.55 K are studied by the static-synthetic method which determines the bubble point via the variable volume cell technique. The experimental bubble points are correlated by the Peng-Robinson (PR) equation of state (EoS) with vdW and MHV2 mixing rules. The modeling results are in good agreement with the measured data. The high temperature VLE of the two binary systems is predicted up to the critical point line by PR-MC-MHV2 model with the optimal binary parameters.

Experimental Phase Equilibrium Data for Rotenone in Supercritical Carbon Dioxide

In this paper, we report data for the phase transition of the binary [rotenone (1) + CO2 (2)] system obtained visually using the static synthetic indirect method and a variable-volume cell at temperatures between 303 and 343 K and pressures near 20 MPa. The molar fraction varied from 1.0 × 10–5 to 2.75 × 10–5. For a molar fraction of rotenone greater than 2.75 × 10–5, the phase transition data could not be measured at pressures of 30 MPa because of the experimental limitations of the equipment. The pressure limitation arose because of the difficulty in solubilizing the system where the solubilization occurs close to or above the limits of the experimental apparatus (30 MPa). The transition of the system was identified as the solid–fluid type, and the phase transition profiles are similar. The Peng–Robinson equation of state (PR-EoS) with the classical mixing rule was used to correlate the experimental data to theory, and excellent agreement was found between the experimental and calculated values.

CO2 influence on asphaltene precipitation

The energy industry has registered a considerable growth of petroleum production from reservoirs located in deep and ultra-deepwater, mainly in Brazil. The Brazilian Pre-Salt fields, specifically, have shown high carbon dioxide content which favors the precipitation of organic particles such as asphaltenes. This scenario has turned flow assurance into a major technical and economic challenge for the exploitation of those fields. In this work a variable-volume cell equipped with a near-infrared probe was used to study the onset of asphaltene precipitation induced by carbon dioxide, evaluating the effects of pressure, temperature, asphaltene concentration, and system composition. Furthermore, the Cubic Plus Association (CPA) was applied to model the asphaltene precipitation. The results show that temperature and the oil model system composition were the parameters that most influenced the asphaltene stability, and that the CPA adequately described the asphaltene precipitation.

High-pressure phase equilibrium data for carbon dioxide + dichloromethane + acetone and carbon dioxide + dichloromethane + acetone + N-acetylcysteine (NAC)

The N-Acetylcysteine (NAC) is a thiol compound with a strong antioxidant effect and demonstrated preventive action as protector in chronic kidney disease, cancer, pulmonary insufficiency, in the treatment of AIDS and other systemic diseases. Experimental phase equilibrium data provide fundamental information for the micronization supercritical fluid SEDS technique, which is characterized by the reduction of the average particle size leads to changes in physical structure of the compounds processed. There are numerous advantages in particle size reduction and make narrower particle size distribution, the main one being the resulting increased bioavailability. Therefore, the aim of this work was to study the high pressure phase behavior of the ternary system {carbon dioxide (1) + dichloromethane (2) + acetone (3)} and for the quaternary system {carbon dioxide (1) + dichloromethane (2) + acetone (3) + NAC (4)} in order to assist the micronization process in supercritical media. The experiments were performed using a variable volume cell over the temperature range from 308 to 328 K, pressure from 4.7 to 9.87 MPa, and mass ratio dichlorometane/acetone of 1.5:1 for the ternary system. For the quaternary system, the same mass ratio of dichlorometane/acetone was adopted and an amount of 0.001 and 0.004 g cm−3 of NAC was added to solution. Phase transitions of vapor-liquid type (bubble or dew points), in the presence or absence of solid phase were observed. The experimental results of the ternary system were modeled using the Peng-Robinson (PR) equation of state with the Wong-Sandler (PR-WS) mixing rule, providing a good representation of the experimental phase equilibrium data.

Carbon dioxide solubilities in tricyanomethanide-based ionic liquids: Measurements and PC-SAFT modeling

This work reports the measurements of the solubility of carbon dioxide (CO2) in three tricyanomethanide based ionic liquids (ILs) constituted by different cations: 1-butyl-3-methylimidazolium, 1-butyl-4-methylpyridinium, 1-butyl-1-methylpyrrolidinium in order to investigate the effect of the cation on the solubility. The solubility of CO2 have been determined using high-pressure variable volume cell in a range of temperature from T = (292.13–367.85) K and pressure up to 121.6 bars. A high solubility of CO2 in the 1-butyl-4-methylpyridinium tricyanomethanide was observed in comparison with the other cation. It was found that the Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) may be used to represent with good accuracy the experimental data of CO2 solubility in tricyanomethanide based ionic liquid.

High pressure vapor-liquid equilibria for binary protic ionic liquids + methane or carbon dioxide

This study reports the high pressure phase transition data for both methane and carbon dioxide and two large protic ionic liquids: N-methyl-2-hydroxyethylammonium propanoate [m-2HEA][Pr] and bis(2-hydroxyethyl)ammonium butanoate [BHEA][Bu]. The experimental data were obtained using the static-synthetic visual method by a variable-volume cell unit. The apparatus and experimental methodology were validated by methane + N-methyl-2-hydroxyethylammonium propanoate equilibrium data. The low deviation between the data indicates the experimental data is consistent with previous literature. Structure and purity of ILs were confirmed by FT-IR spectroscopy, 1H and 13C NMR studies. Water contents were measured by Karl Fischer volumetric measurements. NMRs and water contents analyses were performed on samples collected before and after the experiments. The phase transitions were classified as bubble points and studied at five temperatures from 313.1 to 353.1 K and pressures up to 20 MPa. Experimental data were correlated using the three-parametric Redlich Kwong – Peng Robinson equation of state (RKPR-EoS) coupled to mixing rules van der Waals type, cubic regarding the composition, and temperature dependence for the interaction energy parameter (CMR-T). Henry’s law constants and ideal CO2/CH4 selectivities were calculated from this model and compared to other ILs ones.

Vapor–Liquid Equilibrium of Carbon Dioxide + Ethyl Acetate + Oleic Acid Mixtures at High Pressures

In this work, experimental data for the phase transition of ternary systems {CO2 (1) + ethyl acetate (2) + oleic acid (3)} at global CO2 mole fraction values from 0.5 to 1, at the temperatures of 308, 318, 328, and 338 K are reported. A variable volume cell was used, following the static synthetic method for pressures of up to 21 MPa. The ethyl acetate/oleic acid molar ratio was set to 3:1 [0.750 ethyl acetate + 0.250 oleic acid], 9:1 [0.900 ethyl acetate + 0.100 oleic acid], and 199:1 [0.995 ethyl acetate + 0.005 oleic acid]. In all of these ternary systems, bubble point and dew points were observed.

High pressure phase equilibrium of ternary and multicomponent alkane mixtures in the temperature range from (283 to 473) K

Asymmetric multicomponent alkane mixtures can be used as model systems for reservoir fluids. We have prepared two ternary mixtures, methane/n-butane/n-decane and methane/n-butane/n-dodecane, and two multicomponent mixtures composed of methane/n-butane/n-octane/n-dodecane/n-hexadecane/n-eicosane as model reservoir fluids and measured their phase equilibrium in the temperature range from (283–473) K by using a variable volume cell with full visibility. Their phase envelopes and liquid volume fractions below the saturation pressure have been measured. Four equations of state, including Soave-Redlich-Kwong (SRK), Peng-Robinson (PR), Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT), and Soave-Benedict-Webb-Rubin (Soave-BWR), have been used to predict phase equilibrium of the measured systems. PR and PC-SAFT give better results than others and Soave-BWR gives poor phase envelope predictions which are quite distinct from the predictions by other models. It is generally challenging for any of the tested models to predict all the measured phase envelopes with high accuracy. For predictive calculation of the liquid fractions, the agreement in the low pressure region is good whereas the fractions just below the saturation pressures are difficult to predict. Moreover GERG-2008 has also been tested with the measured methane/n-butane/n-decane system. It overpredicts the saturation pressures but predicts low pressure liquid fractions quite accurately.

Extraction and phase behaviour of Moringa oleifera seed oil using compressed propane

AbstractThis study reports the oil extraction efficiency using Moringa oleifera seed and pressurized propane, new experimental data for phase transition of the binary system {n‐propane + Moringa oleifera oil}, and the profile of fatty acid compositions of the extracted Moringa oil. During the present study, the knowledge of the phase behaviour proved to be of great importance to optimize supercritical extraction using pressurized fluid. This project also compares the classical Soxhlet method including mathematical modelling of kinetic curves of extraction. The extraction experiments were performed in the temperature and pressure ranges of 303–333 K and 2.5–12 MPa, respectively, at a constant flow rate of 1.0 cm3/min of n‐propane. All the conditions applied during the n‐propane extraction process provided similar or higher yields (32.8 to 42.1 %) compared to extractions using n‐hexane (42.6 %) and supercritical carbon dioxide (SC‐CO2) (37.8 %). In addition, phase transition study for the {Propane (1) + Moringa oleífera oil (2)} system was performed using a variable volume cell and the static synthetic method in a temperature range of 303–343 K, pressures up to 3.23 MPa, and n‐propane mass fraction between 0.2 and 0.8. Vapour‐liquid (VLE), liquid‐liquid (LLE), and vapour‐liquid‐liquid (VLLE) phase transitions were observed at relatively low pressures. The fatty acid profiles of the extracted Moringa oils were evaluated using gas chromatography. They all have very close composition regardless of the solvent used and oleic acid as the major component (≈76 %). The Sovová mathematical model indicated a good fit for all the conditions investigated.

Density and phase equilibrium of the binary system methane + n-decane under high temperatures and pressures

Densities of the binary system methane + n-decane have been determined through a vibrating tube densitometer from (278.15–463.15) K at pressures up to 140 MPa, and for methane mole fractions up to 0.8496. Negative excess volumes were found under the experimental conditions studied. Moreover isothermal compressibility values were obtained by differentiation from the Tammann-Tait correlation of the determined density values. Isobaric thermal expansion coefficients were also calculated based on differentiation from the isobaric fit of density data. We also measured the phase equilibrium of this binary system by using a variable volume cell with full visibility from (293.15–472.47) K for three mixtures with methane mole fractions of 0.4031, 0.6021 and 0.8496. Liquid fraction upon expansion below the saturation pressure has also been determined. Finally different equations of state were used to calculate the experimental density and excess volume data as well as the phase envelope data. No direct regression of the experimental data was involved in most of the calculation in order to provide a fair comparison of the performance of different models.

High pressure vapor-liquid equilibria for binary methane and protic ionic liquid based on propionate anions

Sour gases and methane separation has been studied for many years and ionic liquids (ILs) could be used to promote their separation. Protic ionic liquids based on substitute amines and carboxilate anions were reported to be selective to methane/carbon dioxide separation. However, the methane + ILs phase equilibria data, which is required to design gas separation, are scarce on the open literature. This study report the high pressure phase transition data for methane + N-methyl-2-hydroxyethylammonium propanoate, bis(2-hydroxyethyl)ammonium propanoate, or 2-hydroxyethylammonium propanoate. The binary system methane + N-methyl-2-hydroxyethylammonium propanoate was compared to literature experimental data. The structures and purities of ILs were confirmed by 1H NMR, 13C NMR, HSQC and HMBC NMR studies. Water content were measured by Karl Fischer coulometer measurements. The phase transitions have been classified as bubble points and studied at four temperatures from 333.1 to 363.1 K and pressures from 4 to 16 MPa. The experimental data were obtained using the static-synthetic visual method by a variable-volume cell unit. VLE transitions have been classified as bubble points. Henry's law constants were estimated and compared with other ILs and organic solvents. Experimental data for CH4 + + N-methyl-2-hydroxyethylammonium propanoate system were correlated using the three-parametric Redlich – Kwong – Peng – Robinson equation of state (RKPR-EoS) coupled to cubic van der Waals mixing rules (regarding the composition) and temperature dependence for the interaction energy parameter (CMR-T).

Phase behaviour of sesame (Sesamum indicum L.) seed oil using supercritical CO2

ABSTRACTNew experimental data were measured for phase transition of the binary system CO2 + black sesame oil. A variable volume cell was employed using the static synthetic method in a temperature range of 303–333 K, pressures up to 20 MPa, and CO2 mass fractions between 0.12–0.39 g/g. For mass fractions > 0.39, phase transition data were not measured due to pressure limitations of the high‐pressure system used. Vapour‐liquid transitions (VLE) of bubble point (BP) were determined. Phase transition data of CO2 + black sesame oil were compared to reported data from the literature involving CO2 and similar oils. The trend of the phase transition behaviour between all systems compared was similar. Phase equilibrium data obtained experimentally were successfully modelled with the Peng‐Robinson equation of state (PR‐EoS) combined with the van der Waals mixing rule (PR‐vdW2) and Wong‐Sandler mixing rule (PR‐WS).

Measurement and correlation of solid–liquid equilibria for three binaries, ethanol–antipyrine, chloroform–antipyrine, and dimethyl ether–antipyrine

Solid–liquid equilibrium (SLE) was measured for three binaries systems, ethanol–antipyrine, chloroform–antipyrine, and dimethyl ether–antipyrine by use of two apparatus based on a direct temperature measuring method. For dimethyl ether–antipyrine, a high pressure variable volume cell was employed, and the pressure was held constant at 5 MPa. Other measurements were carried out by use of a pressure resistance glass tube at the bubble point pressure. Prior to the measurements, SLE was measured for cyclohexane–naphthalene to ensure the reliability of the method. Comparing the three binary systems containing antipyrine, the molar solubility of antipyrine in chloroform was 1.5 times larger than that in ethanol, and 13.5 times larger than that in dimethyl ether at 313 K. The data were correlated with Schroder-van Laar and NRTL equations under the assumption that the binary system had a simple eutectic temperature. The data could be correlated within 0.168%, 0.775%, and 0.102% in temperature for the ethanol–antipyrine, chloroform–antipyrine, and dimethyl ether–antipyrine binary systems, respectively.

Vapor–liquid equilibrium data for the carbon dioxide and nitrogen (CO2 + N2) system at the temperatures 223, 270, 298 and 303 K and pressures up to 18 MPa

A new setup for the measurement of vapor–liquid phase equilibria of CO2-rich mixtures relevant for carbon capture and storage (CCS) transport conditions is presented. An isothermal analytical method with a variable volume cell is used. The apparatus is capable of highly accurate measurements in terms of pressure, temperature and composition, also in the critical region. Vapor-liquid equilibrium (VLE) measurements for the binary system CO2 + N2 are reported at 223, 270, 298 and 303 K, with estimated standard uncertainties of maximum 0.006 K in the temperature, maximum 0.003 MPa in the pressure, and maximum 0.0004 in the mole fractions of the phases. These measurements are verified against existing data. Although some data exists, there is little trustworthy data around critical conditions, and our data indicate a need to revise the parameters of existing models. A fit made against our data of the vapor–liquid equilibrium prediction of GERG-2008/EOS-CG for CO2 + N2 is presented. At 223 and 298 K, the critical region of the isotherm are fitted using a scaling law, and high accuracy estimates for the critical composition and pressure are found.

Determination of vapor-liquid equilibrium data in microfluidic segmented flows at elevated pressures using Raman spectroscopy.

A fast, noninvasive, and efficient analytical measurement strategy for the characterization of vapor-liquid equilibria (VLE) is presented, which is based on phase (state of matter) selective Raman spectroscopy in multiphase flows inside microcapillay systems (MCS). Isothermal VLE data were measured in binary and ternary mixtures composed of acetone, water, carbon dioxide or nitrogen at elevated pressures up to 10 MPa and temperatures up to 333 K. For validation, the obtained data were compared with literature data and reference measurements in a high-pressure variable volume cell. Additionally, the mixtures were investigated at temperatures and pressures where no data is available in literature to extend the high-pressure VLE database.