Equilibrium Curve Research Articles

Methane Hydrate-in-Oil Systems in the Presence of Natural Amino Acid-Equilibrium Phase Condition Measurements.

This experimental study reports the thermodynamic influence of three different amino acids on methane hydrate in oil-dominated systems, namely, glycine, proline, and alanine. To thoroughly examine the effect of selected amino acids on methane (CH4) hydrate formation compared to the commercial inhibitor monoethylene glycol (MEG) in the presence of oil, the hydrate liquid-vapor equilibrium (H-Lw-Lo-V) curve is used to measure amino acid aqueous solutions. All experiments are performed at a concentration of 10 wt % by using the isochoric T-cycle technique in a high-pressure reactor cell at the selected range of pressures with temperatures of 4.0-9.0 MPa and 276.5-286.0 K, respectively. Results show that all studied amino acids inhibit hydrate formation of methane; the inhibition trend shows as glycine > alanine > proline in both systems; in the brine water system, the inhibition performance was higher than in the pure water system due to the presence of NaCl. Glycine showed the highest inhibition strength in both systems with an average reduced temperature in pure and brine water of 0.92 and 1.75 K, respectively, at 10 wt %, making the inhibition performance of glycine comparable to the commercial inhibitor MEG. The inhibition effect is attributed to the amino acid's hydrogen bonding energies and side group alkyl chain. Calculating the dissociation enthalpies of methane hydrates in the presence of amino acids using the Clausius-Clapeyron equation implies that the amino acids do not occupy the cage structures during methane hydrate formation.

Wave Propagation in Prestressed Structures with Geometric Nonlinearities Through Carrera Unified Formulation

This paper deals with the analysis of wave propagation characteristics in various prestressed structures with geometric nonlinearities using the Carrera Unified Formulation (CUF). CUF provides a versatile platform to model a wide range of structures and nonlinearities that can take care of all wave propagation aspects. In this work, different geometric nonlinearities for which representative governing equations have been derived and numerical solutions have been obtained through a unified approach are considered. The study investigates in detail the effect of prestress and geometric nonlinearity on wave propagation behavior. The results indicate that prestress has a very influential effect on modal frequency and dispersion characteristics for wave propagation. Specifically, three CUF-modeled beams are considered herein, having a sandwich, metallic portal, and metallic box cross section, respectively. Initially, the principal cross-sectional modal shapes of the unstressed, linear, and full nonlinear (i.e., full three-dimensional Green–Lagrange strain matrix) beam with a prestress are investigated, among which torsional and flexural modes can be recognized. Afterward, the equilibrium curves of such structures for various geometrical nonlinear approximations are traced, highlighting that most types of nonlinearity induce a hardening behavior in the system, which increases with the preload, directly leading to a variation in modal frequencies. The dispersion relations of the full nonlinear structure examined as a function of the applied preload are further compared, enriching the investigation by exploiting wave finite element method capabilities. This knowledge paves the way toward the design and optimization of prestressed systems with enhanced acoustic performance, and that fosters the development of sound absorption, noise insulation, and structural isolation.

Calculation of critical endpoints and phase diagrams of highly asymmetric binary systems

The computation of Global Phase Equilibrium Diagrams (GPED) for binary systems, including critical and three-phase equilibrium curves, is crucial for analyzing process conditions and assessing thermodynamic models. In the past two decades, algorithmic strategies and GPEC software have become essential tools. However, numerical problems can arise with the original algorithm for highly asymmetric systems, such as gases or water with heavy compounds or polymers, hindering the completion of GPED and related diagrams.This study presents an innovative calculation methodology to address these challenges. Our approach extends existing algorithms to achieve automatic GPED generation without user intervention, focusing on nearly pure phases. We apply our methodology to systems such as methane or water with heavy alkanes, and CO2 + silicones. The proposed algorithmic strategies effectively handle asymmetric systems, different types of phase behavior, and the estimation of extremely low concentrations in nearly pure phases along the vapor-liquid-liquid equilibrium curve.

Methanol Equilibrium Curves of Power Transformer Oil–Paper Insulation

To eliminate the problem of the aging of cellulose insulation in the manufacturing stage, a new drying method is being developed based on the use of methanol vapors. Previous studies have shown that the complete removal of methanol from the cellulose insulation after the drying process is very difficult. Therefore, it is necessary to check how the remaining methanol after drying affects the properties of both the cellulose materials and mineral oil. To conduct such studies, it is necessary to know the methanol content in oil that can be expected depending on its initial content in the cellulose materials and the temperature of the insulation system. Therefore, the main goal of this work is to develop methanol equilibrium curves for oil–paper insulation. To achieve the assumed goal, three-stage studies were conducted. A gas chromatograph equipped with a flame ionization detector was used in all stages of these studies. The gas partition coefficient between oil and air was determined for a temperature of 70 °C. The key experimental finding was the development of methanol equilibrium curves for oil–paper insulation. Thanks to this achievement, it is possible to estimate the methanol content in cellulose materials and mineral oil depending on the insulation temperature. Such data are necessary, among others, to plan appropriate studies aimed at assessing the impact of methanol content on the dielectric and physicochemical properties of these materials, important from the point of view of the operation of power transformers.

Seismic design of steel moment‐resisting knee‐braced frame system by failure mode control

AbstractThis paper presents the seismic design of a steel moment‐resisting knee‐braced frame (MKF) using the theory of plastic mechanism control (TPMC) within the capacity‐based design framework. The MKF is an alternative system to MRFs, wherein knee elements are utilized to provide rigid connections and enhance lateral stiffness. Capacity‐based design, the predominant approach in current seismic provisions, relies on two key principles: (1) selecting specific structural components as fuses with sufficient ductility to dissipate seismic energy, and (2) ensuring non‐fuse elements can resist the maximum probable reactions from these fuses. The ultimate goal is to achieve a global mechanism where yielding occurs in all structural fuses and at the base of first‐story columns. However, existing seismic design provisions often struggle to fully satisfy the second principle due to the lack of a method for controlling failure modes. TPMC addresses this challenge by ensuring compliance with the second principle, grounding its approach in the kinematic method and the mechanism equilibrium curve within the rigid‐plastic analysis framework. By considering all potential story‐based undesirable mechanisms and calculating the required plastic moment of columns up to a target design displacement, TPMC ensures adherence to the second principle of the capacity‐based design approach, leading to the achievement of a global collapse mechanism. In this paper, an iterative method is proposed for designing beams and knee elements by considering plastic hinges at both ends of the beams, followed by a TPMC‐based methodology for designing columns to ensure a global mechanism. A parametric analysis of a single‐story single‐span MKF explores the effects of knee element geometry ( and ) on component demands. The results indicate that optimal parameter ranges of and can minimize the demands for MKF components. Practical design examples are illustrated using three steel MKFs, each consisting of four, seven, and ten stories with five spans. Pushover analysis and nonlinear dynamic analyses were performed to demonstrate the effectiveness of the proposed design procedure in ensuring the attainment of a global mechanism and excellent seismic performance under real ground motions.

Evaluation of the synergic effect of amino acids for CO2 hydrate formation and dissociation

Gas hydrate formation is a very challenging problem in the oil and gas industry. The chemical inhibition method is the best practicable hydrate mitigation method by injecting hydrate inhibitors such as Thermodynamic Hydrate Inhibitors (THIs) and Kinetic Hydrate Inhibitors (KHIs) into the pipeline. However, the hydrate inhibitors' biodegradability and limited data on dual functional inhibitor mixtures raise concerns in this study. This study aims to investigate and compare thermodynamic and kinetic inhibition on CO2 hydrate by using biodegradable amino acid inhibitor mixtures of Glycine and Alanine. In this study, the inhibitor mixtures were prepared by mixing Glycine and Alanine in 3 different mixture ratios, followed by the Thermodynamic and Kinetic inhibition tests. Thermodynamic Inhibition Test was conducted by using 10 wt% of inhibitor mixtures in a CO2-water system under pressure of 4.0, 3.5, 3.0 and 2.5 MPa, while Kinetic Inhibition Test was carried out by using 1 wt% of the sample in the CO2-water system at a constant pressure of 4.0 MPa and temperatures at 274.15K. The analysis methods for the Thermodynamic Inhibition Test were Hydrate Liquid-Vapor Equilibrium (HLVE) Curve, Average Depression Temperature and Molar Dissociation Enthalpy, while the Induction Time method, the number of CO2 moles consumed, the formation rate of CO2 gas hydrate and RIP were used in the Kinetic Inhibition Test. In this study, all inhibitor mixtures exhibit dual functional inhibition on the CO2 hydrate. For THI, 50% Gly: 50% Ala shows the best thermodynamic inhibition strength with an average depression temperature of 2.42 K. All the inhibitor mixtures for THI have the dissociation enthalpies within the CO2 hydrate enthalpy range, which show that the inhibition is due to the influence on the water molecules’ interaction only. For KHI, 75% Gly: 25% Ala shows the highest kinetic inhibition strength on CO2 formation with the longest induction time of 115.2 min and the highest RIP of 0.40. In the KHI experiment, there is a drop in the CO2 uptake capacity with the presence of inhibitors used, where the highest difference of CO2 moles consumed is 0.0057 mol. A synergistic effect of inhibitor mixtures was observed in this study on 50% Gly: 50% Ala for THI and 75% Gly: 25% Ala for KHI. However, the “degradation” effect was also exhibited on 75% Gly: 25% Ala and 25% Gly: 75% Ala for THI and 50% Gly: 50% Ala and 25% Gly: 75% Ala for KHI, where the performance of the inhibitor mixtures is poorer than the concentrated amino acids. The “degradation” effect of the inhibitor mixtures at certain ratios was not covered in this study and it requires a further understanding of the chemistry behind the inhibition mechanism.

How shallow CO2 hydrate cap affects depressurization production in deeper natural gas hydrate reservoirs: An example at Site W17, South China Sea

The logging results from the Shenhu Sea show that the P-T conditions of NGH deposits are below the CO2 hydrate phase equilibrium curve. The burial depth difference between the CO2 hydrate stable zone and NGH deposits is usually above 100 m, which differs from the laboratory scale. Thus, whether CO2 hydrate caps can provide pore sealing and reinforcement of natural gas hydrate (NGH) overburden at the engineering scale is unknown. Based on this, we aimed to perfect research on the CO2 hydrate cap, including its formation process, effects on NGH exploitation, geomechanical response, and comprehensive benefit evaluation, by establishing a THMC model based on Site W17. Results indicate that (i) CO2 can form hydrates in the overburden layer with a conversion rate of about 28%, preventing the upward escape of residual liquid CO2 due to density difference. (ii) CO2 injection and CO2 hydrate cap formation can increase the decomposition driving force during depressurization to enhance production, but it fails to inhibit water invasion from the upper part of the NGH deposit due to the excessive depth difference. (iii) The CO2 hydrate cap causes strata uplift, thereby mitigating strata subsidence during depressurization production, especially for the cases of horizontal wells, where the subsidence is reduced by about 103.4%. (iv) Injecting too much CO2 may not benefit gas production, where part of the free gas will convert into NGH due to pressure rise. The optimal injection rate in this study is 40,000 m3/d. (v) Indicators like CO2 hydrate conversion rate, gas-water ratio, and maximum strata displacement show that horizontal well systems with CO2 hydrate caps are more beneficial than vertical well systems, and multi-branched well systems are more beneficial than single-direction well systems. These key findings may differ from the laboratory scale, which can provide a reference for applying CO2 hydrate caps in actual NGH exploitation.

Common tenrecs (Tenrec ecaudatus) reduce oxygen consumption in hypoxia and in hypercapnia without concordant changes to body temperature or heart rate.

Common tenrecs (Tenrec ecaudatus) are fossorial mammals that use burrows during both active and hibernating seasons in Madagascar and its neighboring islands. Prevailing thought was that tenrecs hibernate for 8-9months individually, but 13 tenrecs were removed from the same sealed burrow 1m deep from the surface. Such group hibernation in sealed burrows presumably creates a hypoxic and/or hypercapnic environment and suggests that this placental mammal may have an increased tolerance to hypoxia and hypercapnia. Higher tolerances to hypoxia and hypercapnia have been documented for other mammals capable of hibernation and to determine if this is the case for tenrecs, we exposed them to acute hypoxia (4h of 16 or 7% O2), progressive hypoxia (2h of 16, 10 and 4% O2), or progressive hypercapnia (2h of 2, 5 and 10% CO2) at cold (16°C) or warm (28°C) ambient temperatures (Ta). Oxygen equilibrium curves were also constructed on the whole blood of tenrecs at 10, 25, and 37°C to determine if hemoglobin (Hb)-O2 affinity contributes to hypoxia tolerance. In animals held at 16°C, normoxic and normocapnic levels of oxygen consumption rate ( ), body temperature (Tb), and heart rate (HR) were highly variable between individuals. This inter-individual variation was greatly reduced in animals held at 28°C for oxygen consumption rate and body temperature. Both hypoxia (acute and progressive) and progressive hypercapnia led to decreases in as well as the variation in between animals held at 16°C. The fall in oxygen consumption rate in 7% O2 independent of changes in body temperature in tenrecs held at 16°C is unique and not consistent with the typical hypoxic metabolic response seen in other hibernating species that depends on concomitant falls in Tb. In animals held at 28°C, exposure to O2 levels as low as 4% and CO2 levels as high as 10% had no significant effect on , HR, or Tb, indicative of high tolerance to both hypoxia and hypercapnia. High variation in heart rate remained between individuals in all gas compositions and at all temperatures. Tenrec Hb-O2 affinity was similar to other homeothermic placental mammals and likely does not contribute to the increased hypoxia tolerance. Ultimately, our results suggest changes in Ta dictate physiological responses to hypoxia or hypercapnia in tenrecs, responses more characteristic of reptiles than of most placental mammals. Given that numerous anatomical and physiological characteristics of tenrecs suggest that they may be representative of an ancestral placental mammal, our findings suggest the typical hypoxic metabolic response evolved later in mammalian evolution.

Outbursts Upon Cooling of Low‐Temperature Binary Mixtures: Experiments and Their Planetary Implications

AbstractFor many binary mixtures, the three‐phase solid‐liquid‐vapor equilibrium curve has intermediate pressures that are higher than the pressure at the two pure triple points. This curve shape results in a negative slope in the high‐temperature region near the triple point of the less volatile component. When freezing mixtures in the negative slope regime, fluid trapped below confined ice has latent heat released with more vapor upon cooling, and thus increases in pressure. If the rising pressure of the confined fluid overcomes the strength of the confining solid, which may be its own ice, it can produce an abrupt outburst of material and an increase in the system's overall pressure. Here, we report experimental results of freezing‐induced outbursts occurring in the N2/CH4, CO/CH4, and N2/C2H6 systems, and provide insight into the phenomenon through a thermodynamics perspective. We also propose other binary systems that may experience outbursts and explore the geological implications for icy worlds such as Titan, Triton, Pluto and Eris as well as rocky bodies, specifically Earth and Mars.

Thermodynamic and computational approaches to the stability and structural transformation of Xe + large-molecule guest substance (LMGS) hydrates

In this study, the influence of different types of large-molecule liquid substances (LMGSs) and formation conditions on the stability and structural transformation of Xe + LMGS hydrates was investigated using phase equilibria, powder X-ray diffraction (PXRD), 129Xe NMR spectroscopy, and molecular dynamics (MD) simulations. The phase equilibria of Xe hydrates in the presence of three different LMGS types (neohexane [NH], methylcyclopentane [MCP], and methylcyclohexane [MCH]) were measured in the pressure range of 0.1–1.0 MPa. The equilibrium curves of Xe + MCH and Xe + NH hydrates shifted away from that of pure Xe hydrate under low pressure, whereas they coincided with that of pure Xe hydrate under high pressure. Interestingly, the equilibrium curve of Xe + MCP hydrate aligned with that of pure Xe hydrate throughout the pressure range. PXRD and 129Xe NMR analyses demonstrated that the equilibrium curve shift under low pressure was caused by the formation of sH (Xe + LMGS) hydrates, which was attributed to the inclusion of NH or MCH. However, MCP did not participate in sH hydrate formation with Xe. MD simulations revealed that MCP in the large cages did not contribute to the thermodynamic or dynamic stability of sH hydrates. The findings of this study provide valuable insights into the development of hydrate-based noble gas capture and storage.

Adsorption ability of sugar scum as industrial waste for crystal violet elimination: Experimental and advanced statistical physics modeling

Recycling solid industrial waste into useful resources is the most critical aspect of managing waste. Herein, for detoxifying poisonous crystal violet dye (CV) in aqueous media, sugar scum (SS) as an underutilized industrial discard has been tested as a promising adsorbent.The SS was thoroughly analyzed beforehand and after the adsorption process through various characterization techniques. Several operational factors, including pH, biosorbent dosage, dye concentration, and temperature, were optimized, reaching 24 mg.g-1 at (pH 10, 2 g.L−1 of SS, 10 mg.L−1 of CV and 25 °C). The bioadsorbent's performance was assessed through a range of studies involving kinetic, equilibrium (using both conventional and statistical physics models), and thermodynamic investigations.Based on the results, the equilibrium curves best fit the Freundlich model, indicating that multilayer adsorption occurs on a heterogeneous active sites surface. The statistical physics models provided detailed physiochemical insights, the double-layer with two energies model was most accurately describing the data, with a high saturation capability of 371 mg.g−1. Most interactions occur at a single adsorption site (70 %), with the remaining 30 % at two sites, involving both parallel and non-parallel orientations. The mesoporous structure of the SS surface provides an optimum size for CV adsorption. Pore filling, Van der Waals forces, hydrogen bonding, π-π and electrostatic interactions are proposed as the possible mechanisms in the CV-SS system. Thermodynamic measurements indicate that CV adsorption is spontaneous (ΔG° < 0) and exothermic ΔH° (− 41.390 kJ mol−1).The SS recyclability was assessed, exhibiting encouraging sustainability with a slight fall in effectiveness (∼7 %) after 5 sequential usages. Altogether, this study makes a substantial contribution to the promotion of ecological water treatment strategies, which highlights the utility of using SS as an environmental alternative to water contaminant remediation.

Regional Disaster Vulnerability Analysis and Insurance Selection Analysis Based on AHP-EWM-TOPSIS Group Method

Floods, hurricanes, cyclones, and droughts are the most common types of weather, and they have a profound impact on insurance. To specifically analyse the impact, the paper first introduces the concept of Regional Resilience Index (RRI), and then use the AHP-EWM-TOPSIS Method to derive the RRI scores and categorize all regions into five categories based on the size of RRI, which are rock-solid, stable, moderate, weak and vulnerable. Next, the Insurance Break-even Index Evaluation Model is built through the analysis. Insurers should increase their coverage in rock-solid, stable and moderate areas in line with the equilibrium curve, where they should invest in extensive publicity. In weak and vulnerable areas, insurance companies should appropriately reduce policy investment, build a multi-level insurance portfolio such as reinsurance mechanism, and invest a certain amount of funds in regional disaster prevention and loss prevention to maximize the win-win situation between the insurance company and the insured.

Nitric Oxide Ameliorates the Effects of Hypoxia in Mice by Regulating Oxygen Transport by Hemoglobin.

Xiaoying Zhou, Wenting Su, Quanwei Bao, Yu Cui, Xiaoxu Li, Yidong Yang, Chengzhong Yang, Chengyuan Wang, Li Jiao, Dewei Chen, and Jian Huang. Nitric oxide ameliorates the effects of hypoxia in mice by regulating oxygen transport by hemoglobin. High Alt Med Biol. 25:174-185, 2024.-Hypoxia is a common pathological and physiological phenomenon in ischemia, cancer, and strenuous exercise. Nitric oxide (NO) acts as an endothelium-derived relaxing factor in hypoxic vasodilation and serves as an allosteric regulator of hemoglobin (Hb). However, the ultimate effects of NO on the hematological system invivo remain unknown, especially in extreme environmental hypoxia. Whether NO regulation of the structure of Hb improves oxygen transport remains unclear. Hence, we examined whether NO altered the oxygen affinity of Hb (Hb-O2 affinity) to protect extremely hypoxic mice. Mice were exposed to severe hypoxia with various concentrations of NO, and the survival time, exercise capacity, and other physical indexes were recorded. The survival time was prolonged in the 5 ppm NO (6.09 ± 1.29 minutes) and 10 ppm NO (6.39 ± 1.58 minutes) groups compared with the 0 ppm group (4.98 ± 1.23 minutes). Hypoxia of the brain was relieved, and the exercise exhaustion time was prolonged when mice inhaled 20 ppm NO (24.70 ± 6.87 minutes vs. 20.23 ± 6.51 minutes). In addition, the differences in arterial oxygen saturation (SO2%) (49.64 ± 7.29% vs. 42.90 ± 4.30%) and arteriovenous SO2% difference (25.14 ± 8.95% vs. 18.10 ± 6.90%) obviously increased. In ex vivo experiments, the oxygen equilibrium curve (OEC) left shifted as P50 decreased from 43.77 ± 2.49 mmHg (0 ppm NO) to 40.97 ± 1.40 mmHg (100 ppm NO) and 38.36 ± 2.78 mmHg (200 ppm NO). Furthermore, the Bohr effect of Hb was enhanced by the introduction of 200 ppm NO (-0.72 ± 0.062 vs.-0.65 ± 0.051), possibly allowing Hb to more easily offload oxygen in tissue at lower pH. The crystal structure reveals a greater distance between Asp94β-His146β in nitrosyl -Hb(NO-Hb), NO-HbβCSO93, and S-NitrosoHb(SNO-Hb) compared to tense Hb(T-Hb, 3.7 Å, 4.3 Å, and 5.8 Å respectively, versus 3.5 Å for T-Hb). Moreover, hydrogen bonds were less likely to form, representing a key limitation of relaxed Hb (R-Hb). Upon NO interaction with Hb, hydrogen bonds and salt bridges were less favored, facilitating relaxation. We speculated that NO ameliorated the effects of hypoxia in mice by promoting erythrocyte oxygen loading in the lung and offloading in tissues.

Determination of hydrate phase equilibrium (H-L-V) data for the binary CO2–CH4 gas mixture in the presence of 1,3 dioxolane

Present work details the determination of three phase hydrate equilibrium data (H-L-V) using temperature search method for the binary CO2/CH4 gas mixture (50:50 molar ratio) in presence of 1,3 dioxolane (DIOX). DIOX concentration used for phase equilibrium determination were 1,3 and 5.56 mol% respectively. In the presence of DIOX, it was observed that phase equilibrium curve was shifted right with respect to the curve using same gas mixture with no additive (pure water). This indicates that the presence of DIOX moderates the hydrate formation equilibrium conditions. Also, as DIOX concentration increases from 1 mol% to 5.56 mol%, a decrement in phase equilibrium pressure at same temperatures was observed, confirming the potential of DIOX as an effective thermodynamic promoter. Enthalpy of hydrate dissociation was calculated for CO2/CH4 gas mixture in presence of DIOX using Clausius- Clapeyron plot and it was found to be 90.81±6.55 KJ/mol which confirms the sII structure of CO2-CH4-DIOX mixed hydrate. Besides providing the phase equilibrium data of formed hydrates with CO2/CH4 gas mixture using different concentration of DIOX, the present study will aid in determining suitable experimental conditions for examining kinetics and performing separation studies of CO2/CH4 gas mixture through hydrate formation.

Drug–polymer compatibility prediction via COSMO-RS

In this work, the solid–liquid equilibrium (SLE) curve for ten active pharmaceutical ingredients (APIs) with the polymer polyvinylpyrrolidone (PVP) K12 was purely predicted using the Conductor-like Screening Model for Real Solvents (COSMO-RS). In particular, two COSMO-RS-based strategies were followed (i.e., a traditional approach and an expedited approach), and their performances were compared. The veracity of the predicted SLE curves was assessed via a comparison with their respective SLE dataset that was obtained using the step-wise dissolution (S-WD) method. Overall, the COSMO-RS-based API–PVP K12 SLE curves were in satisfactory agreement with the S-WD-based data points. Of the twenty predicted SLE curves, only two were found to be in strong disagreement with the corresponding experimental values (both modeled using the expedited approach). Hence, it was recommended to use the traditional approach when predicting the API–polymer SLE curve. At the present moment, COSMO-RS may be an effective computational tool for the expeditious screening of API–polymer compatibility, particularly in the case of promising novel APIs, for which experimental datasets are likely limited or non-existent.

A High–Throughput Molecular Dynamics Study for the Modeling of Cryogenic Solid Formation

To predict the favorable thermodynamical conditions and characterize cryogenic pellet formations for applications in nuclear fusion reactors, a high–throughput molecular dynamics study based on a unified framework to simulate the growth process of cryogenic solids (molecular deuterium, neon, argon) under gas pressure have been designed. These elements are used in fusion nuclear plants as fuel materials and to reduce the damage risks for the plasma-facing components in case of a plasma disruption. The unified framework is based on the use of workflows that permit management in HPC facilities, the submission of a massive number of molecular dynamics simulations, and handle huge amounts of data. This simplifies a variety of operations for the user, allowing for significant time savings and efficient organization of the generated data. This approach permits the use of large-scale parallel simulations on supercomputers to reproduce the solid–gas equilibrium curves of cryogenic solids like molecular deuterium, neon, and argon, and to analyze and characterize the reconstructed solid phase in terms of the separation between initial and reconstructed solid slabs, the smoothness of the free surfaces and type of the crystal structure. These properties represent good indicators for the quality of the final materials and provide effective indications regarding the optimal thermodynamical conditions of the growing process.

Hydrate phase equilibrium measurement of 50 mol.% carbon dioxide / 33 mol.% dimethyl ether / 17 mol.% propane in the presence of tetrahydrofuran, cyclopentane, tetra‑n‑butylammonium bromide, and tetra‑n‑butylammonium chloride

Hydrate-based cold storage and refrigeration offer notable efficiency and safety advantages. By leveraging the high cold storage density of CO2 hydrate and the low phase equilibrium pressure and GWP of DME and C3H8 hydrates, a gas mixture hydrate (50 mol.% CO2, 33 mol.% DME, 17 mol.% C3H8) was used as a refrigerant for phase equilibrium assessment. Results showed phase equilibrium temperatures of 274.5 to 278.9 K at pressures from 0.4 to 0.86 MPa, aligning with conventional air conditioning pressures. Additives like THF, CP, TBAB, and TBAC improved conditions. Liquid promoters (THF, CP) increased temperatures by 4.5 to 7.9 K, while solid promoters (TBAB, TBAC) raised them by 5.3 to 11.1 K. Liquid promoters shifted the phase equilibrium curve for CO2-DME-C3H8 hydrate almost parallel to the right, while solid promoters steepened the curve slope. A predictive model was developed, showing good molar phase change enthalpy.

Equilibrium curves and modeling of binary systems for the carbon di-oxide + benzyl acetoacetate and carbon di-oxide + benzyl acetate mixtures under high pressure

The solution phase behavior of the binary systems of supercritical carbon di-oxide (SU-CO2) + benzyl acetoacetate and SU-CO2 + benzyl acetate was investigated in a synthetic high-pressure apparatus at five temperatures from 313.2 to 393.2 K and pressure up to 33.53 MPa for the industrial benefit of food, pharmaceutical and cosmetics application. The solubility of benzyl acetoacetate and benzyl acetate in the SU-CO2 + benzyl acetoacetate and SU-CO2 + benzyl acetate systems were increased with increasing temperature at constant pressure, respectively. Both system isotherms were exhibited in the simple Type-I category phase behavior. Besides, the Peng-Robinson equation of state has been successfully applied to predict the phase behavior of the SU-CO2 + benzyl ester systems using adjustable molecular interaction parameters (kij and ηij). Neither system shows a three-phase behavior at any point of temperature and pressure. A one-fluid-phase locale was ascertained above and throughout the solubility curve whereas a two-phase locale was exhibited inside the critical curve for both binary systems. The critical mixture curve provides the fingerprint for the phase behavior study of any binary system since it is used to understand and calculate thermodynamic properties effectively. The accuracy of the studied model was tested by evaluating the percentage of root mean square deviation utilizing optimized temperature-dependent mixture parameters. Indeed, this is the first reference point for the prediction of phase transition behavior for benzyl acetoacetate and benzyl acetate in SU-CO2 and the findings make a remarkable impression on industrial applications.

Crystallization resolution of racemic compounds via chiral surfactant

As one of the basic attributes of nature and the universe, chirality is valuable in biology, medicine, and materials science. However, enantiomer resolution remains a long-standing challenge. Herein, a novel surfactant for resolution of racemic compound with high performance has been outlined. Firstly, we synthesized a chiral surfactant and its chiral recognition ability to L-Alanine molecules was confirmed. Subsequently, the solid–liquid equilibrium curves were used to design the resolution route. The synthesized surfactant was further utilized to intensify the crystallization process of the racemic compound, resulting in a remarkable increase of L-Alanine products’ ee values from 0% to 99%. Finally, quantum chemical calculations and molecular dynamics simulations were employed to uncover the stereoselectivity recognition mechanism of surfactant to L-Alanine molecules. Overall, we propose a new idea for direct crystallization resolution of racemic Alanine by chiral surfactants that differs from the “rule of reversal”, which is highly attractive for chiral resolution.

Separation of free fatty acids and neutral lipids from an aqueous suspension of crude microalgae oil with ethyl acetate

The aim of this study was to determine the liquid-liquid equilibrium data for a ternary system of water, ethyl acetate and oil from the microalgae Scenedesmus obliquus at 298.15, 308.15, and 318.15 K. The potential of the ternary system was also investigated for the selective extraction of free fatty acids and neutral lipids from crude microalgae oil. The equilibrium data were obtained using a model oil formulated from a mixture of refined vegetable oils, with a fatty acid profile analogous to the dark and opaque algae oil. The experimental equilibrium curves and tie lines were provided as a function of temperature for a free fatty acid content of 2%, 20% and 40% (w/w). The free fatty acids in the model oil migrated preferentially to the ethyl acetate-rich phase in each of the systems under study, with extraction efficiencies ranging from 79.4% to 97.1%. However, the extraction efficiencies for the neutral lipids were lower (51.5–70.1%), indicating the preferential extraction of free fatty acids. The distribution coefficients of neutral lipids (1.06–2.34) and free fatty acids (3.85–33.2) were determined in order to better understand the selectivity of the green solvent, ethyl acetate, in the purification of crude oil from algae. The selectivity values varied from 1.84 to 28.6, indicating that the solvent was effective in concentrating neutral lipids and free fatty acids in the ethyl acetate-rich phase. The increase in free fatty acid content therefore reduced the partition coefficient for neutral lipids, improving its selectivity, and making it possible to concentrate this lipid class by liquid-liquid separation with ethyl acetate.