The high-pressure phase behavior of the ternary system constituted by carbon dioxide + globalide + chloroform was studied. Experiments were conducted applying the synthetic-visual method in a ...variable-volume view cell at a mass ratios of globalide to chloroform of 0.5:1, 1:1, and 2:1, over a temperature range from 313.15 to 343.15 K, and pressures from 5.17 to 20.25 MPa. Phase transitions of vapor–liquid bubble point (VLE-BP), vapor–liquid dew point (VLE-DP), liquid–liquid (LLE), and vapor–liquid-liquid (VLLE) type were observed. Furthermore, through the P-w diagram, the phase behavior of the ternary system in chloroform free-basis was analyzed between 0.4250 to 0.9735 of carbon dioxide mass composition. It has been observed that high quantities of chloroform lead to lower transition pressures. Moreover, PT-diagrams efficiently displayed that higher pressures are necessary to achieve a single phase medium as temperature rises, which characterize LCST behavior. PR-vdW2 model was used to estimate binary interaction parameters. Additionally, the ternary system was compared with binary systems available in the literature. The data presented in this work provides necessary information for the optimization and improvement of poly(globalide) synthesis in supercritical media.
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•Data for the phase equilibrium of the ternary systems CO2 + globalide + chloroform.•Measured at temperatures from 313.15 to 343.15 K and pressures up to 20.25 MPa.•Experimental data were correlated using PR-EoS with vdW2 mixing rule.•Chloroform has been shown to be effective in decreasing phase transition pressures.
Mg(MgxZn1-x)2P2 was found to be a key material in Zn3P2-based solar cells, which have attracted attention as an earth-abundant photovoltaic technology. However, Mg(MgxZn1-x)2P2 has not been ...investigated as a functional material thus far, and even the single-phase range in the Mg–P–Zn equilibrium phase diagram is currently unknown. Thus, in this work, we investigate the phase equilibria around Mg(MgxZn1-x)2P2 in the Mg–P–Zn system using Sn as a flux for equilibrium experiments. We find that Mg(MgxZn1-x)2P2 exists as a single phase with a trigonal P3‾m1 structure from x = 0 to x = 0.55 based on our XRD and the SEM-EDS analyses. The lattice parameters, a and c, monotonically increase with increase in the Mg content. In addition, the Mg(MgxZn1-x)2P2 phase can equilibrate with Zn3P2 only in the case of x = 0 (MgZn2P2) despite the wide composition range available. The lattice mismatch between MgZn2P2 and Zn3P2 is about 0.5%, which is consistent with our previous results of an electron diffraction study on Mg(MgxZn1-x)2P2/Zn3P2 interfaces. We also find that the interface between Mg and Mg(MgxZn1-x)2P2 is unstable and that the interface reaction is expected to result in the formation of the Mg-rich phosphide phase, which is air- and water-sensitive. The instability of the reaction product in the atmosphere can degrade the device via the formation of voids around the interface, which was observed in our previous work. Therefore, we deduce that Mg is not suitable as the surface electrode of Mg(MgxZn1-x)2P2/Zn3P2 solar cells. The phase equilibria established in this study can aid in redesigning the device structure of Zn3P2-based solar cells and in further investigation of the physical properties of Mg(MgxZn1-x)2P2.
Mg(MgxZn1-x)2P2 is a crucial material in Zn3P2-based solar cells. In this study, we clarify the single-phase composition range and the lattice constants of the Mg(MgxZn1-x)2P2 and the related phase equilibria in the Mg–P–Zn system, which are essential to design photovoltaic devices using Mg(MgxZn1-x)2P2 and Zn3P2. Display omitted
The use of polymeric materials inevitably leads to environmental impacts, which can be significant and may worsen over time. Therefore, the application of biocompatible and biodegradable polymers, as ...well as the study of alternative polymerization methods, has become extremely relevant in reducing negative consequences to the environment. Among these polymers, poly(ε-caprolactone), also known as PCL, has gained prominence in recent years, particularly due to its range of applications in the biomedical field. In this context, the aim of this work is to contribute to the current state of the art in the literature on high-pressure experimental data of ε-caprolactone/CO2 system, with the goal of facilitating polymerization reactions in supercritical medium. The experiments were carried out using a variable volume view cell operating in the temperature range of 313.15 to 343.15 K and at pressures from 6.65 to 22.72 MPa. The behavior of the binary system was analyzed using a P−x and PT diagrams. Vapor-liquid bubble point (VLE-BP) and dew point (VLE-DP) phase transitions were observed. Furthermore, the Peng-Robinson equation of state (EoS) with the Wong-Sandler (PR-WS) mixing rule was employed to model the phase equilibrium data obtained for the systems. This approach provides an accurate representation of the experimental phase equilibrium data.
•Phase behavior experimental data of the {CO2 + Acetone + Efavirenz} System at High-Pressures.•The experimental data were modeled with the GC-VT-PR EoS and PC-SAFT equation of state.•Thermodynamic ...data are of great relevance for particle engineering in supercritical fluids.
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.
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•A comprehensive review on hydrate based hydrogen (H2) storage is presented.•State of the art for various H2-containing hydrate systems are evaluated.•Multiple cage occupancy by H2 ...and the tuning effect are discussed systematically.•Challenges, limitations, and future directions for the technology are outlined.•Solid-HyStore technology is recommended for stationary storage of hydrogen.
With non-renewable fossil fuels depleting rapidly, hydrogen as a clean energy source producing no pollutants or greenhouse gas emissions upon combustion is bound to play a leading role in the future energy landscape. Among the pertinent challenges in establishing a hydrogen-based economy is developing an energy dense hydrogen storage technology with easy recovery of the stored gas. Clathrate hydrates enabling the innovative solidified storage of hydrogen molecules at moderate temperature and pressure conditions carve a niche for safe, long-term, stationary hydrogen storage. This review focuses on the current state of the art for solidified hydrogen storage (Solid-HyStore) via clathrate hydrates. The properties and performances of various H2-containing hydrate systems are evaluated and summarized comprehensively. Multiple cage occupancy by H2 molecules and the tuning effect as the controversial issues in hydrogen hydrate research are elucidated. Finally, the challenges, limitations, and future opportunities for hydrate-based hydrogen storage are identified.
•A thorough review on the whole hydrogen energy chain to figure out the potential existence of phase transition and application of phase equilibrium studies.•A thermodynamically-consistent flash ...calculation scheme to calculate phase equilibrium states with physical meanings.•Predictions of phase equilibrium states in practical hydrogen production, storage and transportation applications.•Suggestions to the hydrogen industry for different engineering purposes based on the phase equilibrium calculations.
In this paper, a thorough review of the current state of the hydrogen phase equilibrium approaches is presented. Potential applications of phase equilibrium calculations for the accurate simulation of the entire process are then identified. Based on the first and second laws of thermodynamics, an advanced constant (N), volume (V), and temperature (T) (NVT) flash calculation scheme is developed for fluid mixtures containing hydrogen, which can be used to calculate the phase equilibrium for various feed compositions. We produce reasonable predictions of the phase transition under various environmental conditions for a number of engineering scenarios during the hydrogen production and storage processes, thus demonstrating the effectiveness and robustness of the proposed phase equilibrium calculation scheme.
High-pressure phase equilibrium and volumetric properties are fundamental to developing high-pressure and high-temperature (HPHT) reservoirs. In this work, we extended our previous study on methane ...(CH4) + stock tank oil (STO) to two other highly asymmetric light gas-STO systems: nitrogen (N2) + STO and carbon dioxide (CO2) + STO. We systematically measured their phase equilibrium and densities at temperatures from (298.15 to 463.15) K and pressures up to 140 MPa. The nitrogen mole fraction varies from 0.20 to 0.31 for the density measurement and from 0.21 to 0.40 for the phase equilibrium measurement. The carbon dioxide mole fraction varies from 0.20 to 0.70 for the density measurement and from 0.21 to 0.70 for the phase equilibrium measurement. We also determined the isothermal compressibilities and pseudo-excess volumes from the experimental densities. The measured data were modeled by the Soave-Redlich-Kwong (SRK) equation of state (EoS), the Peng-Robinson (PR) EoS, their volume translated versions SRK-VT and PR-VT, and the Perturbed Chain Statistical Associating Fluid Theory (PC-SAFT) EoS. For density, SRK and PR gave large deviations of ∼16% and ∼7%, respectively, compared with ∼3% for PC-SAFT and PR-VT and ∼1% for SRK-VT. The overall deviations for isothermal compressibility were in the range of 20∼34% for all the models, with larger deviations for N2+STO. SRK, PR, and PC-SAFT gave similar small deviations for pseudo-excess volumes. Using the excess volume method, these models could accurately estimate the live oil densities from the STO densities, showing an average deviation of ∼0.5%. The deviations in predicted saturation pressures varied in a large range (4∼16%), with PC-SAFT better for N2+STO and SRK/PR better for CO2+STO. The measured data and model comparison results are valuable for improving the phase behavior description for HPHT reservoir fluids and gas injection processes.
•First study on obtaining experimental phase equilibrium data for propane + globalide system.•Data have been obtained at temperatures from 313.15 to 343.15 K and pressures from 0.6 to ...2.5 MPa.•PR-vdW1 EoS provided good representation of the phase behavior for the studied system.•This study enabled setting optimum system pressures for globalide polymerization in pressured propane.
Globalide is a macrolactone used recently as a monomer in polymerization processes in several kinds of research due to its ability to produce biodegradable and biocompatible polyesters suitable for applications in biodegradable packaging and biomedical devices. Polymerization processes traditionally use organic solvents and metallic/chemical catalysts that may leave toxic residues in the final polymer. To obtain polymers free of organic solvents, the use of pressurized gasses as green solvents has been investigated. In this context, knowing the phase behavior of these systems is essential to understand the proper conditions of the polymerization process, ensuring that the reaction occurs in single-phase conditions. This work reports phase equilibrium studies of Gl + propane systems at temperatures of 313.15, 323.15, 333.15, and 343.15 K, and propane mass fractions between 0.1 and 0.9001. All observed phase transitions occur in pressures lower than 2.5 MPa, indicating that propane is a solvent that requires less energy expenditure than systems with CO2, being an economic advantage in the polymerization process. Peng-Robinson equation of state with a constant binary interaction parameter adjusted adjustment to the experimental data well.
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A titanium composite alloy (Ti –Al –Si – Zr) manufacturing process using eutectic solidification was studied by simultaneous thermal analysis up to 1480 °C. Phase transformations predicted by ...sections of the phase stability diagram (ThermoCalc optimisation) have been observed. The structure of the alloy was also studied by scanning electron microscopy (SEM), light optical microscopy (LOM) and X-ray microanalysis. Several patterns, unexplained on the basis of the stable phase diagrams of the system, are revealed to be associated with metastable phase transformations. The results can be used for a determination of composite applications and the optimisation of its casting technology.
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•Mixed methane/1, 3-dioxolane hydrate formation was studied at high temperatures.•The optimum L-tryptophan concentration for hydrate formation was identified.•Rapid hydrate formation ...at near-ambient temperature was demonstrated.•86.8% of the theoretical maximum methane storage capacity was achieved.•Better kinetic performance is warranted for hydrate formation from saline water.
Gas storage technologies are vital to a modern energy security and resilience framework. Natural gas storage via clathrate hydrates, also known as Solidified Natural Gas (SNG), is attractive because of its non-explosive nature and high volume density. 1,3-dioxolane (DIOX), an additive with low volatility and less toxicity, has recently emerged as a promising dual-function (thermodynamic and kinetic) promoter for hydrate formation. Herein, we investigate mixed CH4/DIOX (sII) hydrate formation at, a) elevated temperature conditions, and b) introducing 3 wt% NaCl to the system (simulated seawater conditions). Hydrate formation from an aqueous solution containing 5.56 mol% DIOX and 1000 ppm L-tryptophan resulted in an average final methane uptake of 99.76 (±2.85) (v/v; volume of gas at STP/volume of hydrate), when the experimental temperature and methane overpressure employed were 293.15 K and 6.6 MPa, respectively. This equates to 86.8% of the theoretical limit for mixed CH4/DIOX (sII) hydrates. The average time required for 90% completion of the gas uptake was only 39.89 (±0.96) min. For experiments conducted in the presence of 3.0 wt% NaCl (a thermodynamic inhibitor), the final gas uptake was expectedly lower when compared to the counterpart freshwater system. This was somewhat offset by elevating the initial driving force and adding 1000 ppm of L-tryptophan. The rapid and high-volume methane uptake achieved at near ambient temperature significantly propels the viability of using the mixed CH4/DIOX system for hydrate based natural gas storage. However, further improvement in the kinetic performance is warranted to negotiate hydrate formation from saline water.
