Recent publications have reported phase equilibrium data for CO₂ + methylcyclopentane (MCP) and CO2 + 2,2-dimethylbutane using static-analytical sampling methods that are inconsistent with previously published synthetic-method data. To verify the reliability of our earlier measurements, we have repeated vapor–liquid equilibrium (VLE) experiments for both CO₂ + MCP and CO₂ + 2,2-dimethylbutane in the range 20–90 °C using a high-pressure variable-volume PVT cell with visual observation. Our new data agree within 1–2 bar with the values previously reported by our group, confirming the reproducibility of the synthetic method. To further validate our methodology, we also investigated the CO₂ + toluene system, which has been extensively studied in the literature. Our experimental results are in agreement with reference data, thereby confirming the accuracy of the synthetic technique and of the procedures used for mixture preparation and bubble-point detection. These results support the conclusion that the discrepancies between our data and those obtained by static-analytical methods cannot be attributed to errors inherent to the synthetic technique.
{"title":"Validation of synthetic method for phase equilibria measurements: Re-examination of CO₂ + methylcyclopentane, CO₂ + 2,2-dimethylbutane, and benchmarking with CO₂ + toluene","authors":"Jean-Luc Daridon , Jean-Patrick Bazile , Jean-Noël Jaubert , Stéphane Vitu","doi":"10.1016/j.fluid.2026.114664","DOIUrl":"10.1016/j.fluid.2026.114664","url":null,"abstract":"<div><div>Recent publications have reported phase equilibrium data for CO₂ + methylcyclopentane (MCP) and CO<sub>2</sub> + 2,2-dimethylbutane using static-analytical sampling methods that are inconsistent with previously published synthetic-method data. To verify the reliability of our earlier measurements, we have repeated vapor–liquid equilibrium (VLE) experiments for both CO₂ + MCP and CO₂ + 2,2-dimethylbutane in the range 20–90 °C using a high-pressure variable-volume PVT cell with visual observation. Our new data agree within 1–2 bar with the values previously reported by our group, confirming the reproducibility of the synthetic method. To further validate our methodology, we also investigated the CO₂ + toluene system, which has been extensively studied in the literature. Our experimental results are in agreement with reference data, thereby confirming the accuracy of the synthetic technique and of the procedures used for mixture preparation and bubble-point detection. These results support the conclusion that the discrepancies between our data and those obtained by static-analytical methods cannot be attributed to errors inherent to the synthetic technique.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"605 ","pages":"Article 114664"},"PeriodicalIF":2.7,"publicationDate":"2026-01-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ethyl alcohol and water form an azeotropic mixture that is widely used in industry. The present study reports a series of entrainers for triethylene glycol (TEG) and TEG-based deep eutectic solvents (DESs) for separation of ethyl alcohol and water. The choline chloride (ChCl):TEG with a molar ratio of 1:3 was selected as the DES-based system and was assumed as pseudo-pure component system. These two entrainers, TEG and ChCl:TEG (1:3), were investigated to separate the ethyl alcohol and water with the entrainer concentration was up to 30 wt%. The vapor-liquid equilibrium (VLE) data were measured using a modified Othmer-recirculation still ebuilliometer at 101.3 kPa. The VLE data were also validated using the L-W Wisniak and Van Ness consistency test. With an additional of entrainer, the ethyl alcohol + water azeotropic point was shifted for TEG (15 wt% and 30 wt%) and ChCl:TEG 1:3 (15 wt%). While the break point of azeotrope of ethyl alcohol + water was observed for ChCl:TEG 1:3 (30 wt%). Two thermodynamic models, the non-random two liquids (NRTL) and universal quasi-chemical (UNIQUAC) were well-correlated with VLE data. In addition, the sigma profile (σ) and the reduced density gradient (RDG) analysis were also performed the molecular interaction of ethyl alcohol, water, and entrainer with strong hydrogen bonding.
{"title":"Separation of ethyl alcohol/water azeotropic mixture using triethylene glycol and triethylene glycol-based deep eutectic solvent: Vapor-liquid equilibria and molecular interactions","authors":"Serli Dwi Rahayu , Onjira Sopakayang , Hong-Ming Ku , Ardila Hayu Tiwikrama","doi":"10.1016/j.fluid.2026.114659","DOIUrl":"10.1016/j.fluid.2026.114659","url":null,"abstract":"<div><div>Ethyl alcohol and water form an azeotropic mixture that is widely used in industry. The present study reports a series of entrainers for triethylene glycol (TEG) and TEG-based deep eutectic solvents (DESs) for separation of ethyl alcohol and water. The choline chloride (ChCl):TEG with a molar ratio of 1:3 was selected as the DES-based system and was assumed as pseudo-pure component system. These two entrainers, TEG and ChCl:TEG (1:3), were investigated to separate the ethyl alcohol and water with the entrainer concentration was up to 30 wt%. The vapor-liquid equilibrium (VLE) data were measured using a modified Othmer-recirculation still ebuilliometer at 101.3 kPa. The VLE data were also validated using the L-W Wisniak and Van Ness consistency test. With an additional of entrainer, the ethyl alcohol + water azeotropic point was shifted for TEG (15 wt% and 30 wt%) and ChCl:TEG 1:3 (15 wt%). While the break point of azeotrope of ethyl alcohol + water was observed for ChCl:TEG 1:3 (30 wt%). Two thermodynamic models, the non-random two liquids (NRTL) and universal quasi-chemical (UNIQUAC) were well-correlated with VLE data. In addition, the sigma profile (σ) and the reduced density gradient (RDG) analysis were also performed the molecular interaction of ethyl alcohol, water, and entrainer with strong hydrogen bonding.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114659"},"PeriodicalIF":2.7,"publicationDate":"2026-01-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145972935","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chemical process design relies on accurate knowledge of physical properties; however, it is unknown for a process to have both a single dominant property and broad range of well-documented properties. Supercritical extraction is one such case: while solubility data for essential-oil components in CO2 are available, information on other physical properties remains limited. This study investigates the previously unreported density of homogeneous-phase fluid mixtures as an additional key property, using limonene and linalool as representative essential-oil components. Densities of the CO2/limonene and CO2/linalool binary systems are measured with a high-pressure oscillating density apparatus equipped with a circulating pump and variable-volume observation cell. The obtained data is correlated using the perturbed chain-statistical associating fluid theory equation of state, which requires pure-component parameters for each component. Pure-component parameters are often reported in sets obtained through different methods, and limonene and linalool likewise have multiple sets reported. In conventional physical property estimation, a single set is often selected ad hoc with little acknowledgment of the existence of alternative sets. This study examines the impact of pure-component parameter selection on density estimation by performing density correlation on mixtures using each available set of pure-component parameters. The accuracy of the mixture density correlation depends on the precision of the pure-component density estimation, although mixture-related parameters can partially compensate for such deviations. These findings demonstrate the importance of accurate pure-component parameters and complementary role of mixture parameters in improving the reliability of thermodynamic modeling for supercritical CO2 systems.
{"title":"Density measurements of homogeneous-phase fluid mixtures comprising CO2/limonene and CO2/linalool binary systems and correlation with the PC-SAFT equation of state","authors":"Hiroaki Matsukawa , Ken Kuwabara , Tomoya Tsuji , Katsuto Otake","doi":"10.1016/j.fluid.2025.114658","DOIUrl":"10.1016/j.fluid.2025.114658","url":null,"abstract":"<div><div>Chemical process design relies on accurate knowledge of physical properties; however, it is unknown for a process to have both a single dominant property and broad range of well-documented properties. Supercritical extraction is one such case: while solubility data for essential-oil components in CO<sub>2</sub> are available, information on other physical properties remains limited. This study investigates the previously unreported density of homogeneous-phase fluid mixtures as an additional key property, using limonene and linalool as representative essential-oil components. Densities of the CO<sub>2</sub>/limonene and CO<sub>2</sub>/linalool binary systems are measured with a high-pressure oscillating density apparatus equipped with a circulating pump and variable-volume observation cell. The obtained data is correlated using the perturbed chain-statistical associating fluid theory equation of state, which requires pure-component parameters for each component. Pure-component parameters are often reported in sets obtained through different methods, and limonene and linalool likewise have multiple sets reported. In conventional physical property estimation, a single set is often selected ad hoc with little acknowledgment of the existence of alternative sets. This study examines the impact of pure-component parameter selection on density estimation by performing density correlation on mixtures using each available set of pure-component parameters. The accuracy of the mixture density correlation depends on the precision of the pure-component density estimation, although mixture-related parameters can partially compensate for such deviations. These findings demonstrate the importance of accurate pure-component parameters and complementary role of mixture parameters in improving the reliability of thermodynamic modeling for supercritical CO<sub>2</sub> systems.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114658"},"PeriodicalIF":2.7,"publicationDate":"2025-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145921806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-24DOI: 10.1016/j.fluid.2025.114657
Peter Förster , William Graf von Westarp , Janik Hense , Johannes von Campenhausen , Andreas Jupke
Liquid-liquid equilibrium (LLE) data were experimentally determined for ternary systems containing 2,3-butanediol (2,3-bdo) or acetoin as solutes, water and 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol as solvents, at 298.2 K and atmospheric pressure. Distribution coefficients increased with decreasing carbon-chain length of the solvents, ranging from 0.2610 (1-decanol) to 0.3827 (1-heptanol) for 2,3-bdo and from 0.2817 (1-decanol) to 0.4252 (1-heptanol) for acetoin. Acetoin exhibited higher maximum distribution coefficients (0.4252 in 1-heptanol) and selectivities (7.9429 in 1-decanol) compared to 2,3-bdo (0.3827 in 1-heptanol and 4.5745 in 1-heptanol, respectively). Trends are consistent with solute functionality and solvent polarity. Experimental LLE data were correlated using the NRTL activity coefficient model, and the binary interaction parameters were successfully regressed. A topological analysis confirmed the consistency of the model correlations at 298.2 K.
{"title":"Liquid-liquid equilibrium of water + 2,3-butanediol + n-alcohols (1-heptanol, 1-octanol, 1-nonanol, 1-decanol) and water + acetoin + n-alcohols ternary systems at 298.2 K","authors":"Peter Förster , William Graf von Westarp , Janik Hense , Johannes von Campenhausen , Andreas Jupke","doi":"10.1016/j.fluid.2025.114657","DOIUrl":"10.1016/j.fluid.2025.114657","url":null,"abstract":"<div><div>Liquid-liquid equilibrium (LLE) data were experimentally determined for ternary systems containing 2,3-butanediol (2,3-bdo) or acetoin as solutes, water and 1-heptanol, 1-octanol, 1-nonanol, and 1-decanol as solvents, at 298.2 K and atmospheric pressure. Distribution coefficients increased with decreasing carbon-chain length of the solvents, ranging from 0.2610 (1-decanol) to 0.3827 (1-heptanol) for 2,3-bdo and from 0.2817 (1-decanol) to 0.4252 (1-heptanol) for acetoin. Acetoin exhibited higher maximum distribution coefficients (0.4252 in 1-heptanol) and selectivities (7.9429 in 1-decanol) compared to 2,3-bdo (0.3827 in 1-heptanol and 4.5745 in 1-heptanol, respectively). Trends are consistent with solute functionality and solvent polarity. Experimental LLE data were correlated using the NRTL activity coefficient model, and the binary interaction parameters were successfully regressed. A topological analysis confirmed the consistency of the model correlations at 298.2 K.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114657"},"PeriodicalIF":2.7,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881392","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-23DOI: 10.1016/j.fluid.2025.114656
Yuan Wei , Xuan Li , Shuangli Yue , Xue Wu , Xiangyu Huo
Knowledge of the solubility evolution of elemental sulfur in natural gas is the theoretical basis for preventing sulfur deposition in high-sulfur carbonate gas reservoir developments. In addition to temperature, pressure and composition, confinement nanopore throats also affects the sulfur solubility. All-atom equilibrium molecular dynamic simulations are conducted to study the solubility of elemental sulfur in H2S confined in calcite slit nanopores under reservoir conditions. The sulfur solubility in the calcite pore reduces with slit aperture, and it is dramatically larger than that in the unconfined bulk system. The molecular mechanism of the over-solubility of sulfur is identified as the adsorption-driven effect of solute molecules, which is revealed through analysis on the interaction between the solute/solvent and calcite surface, the particle structure distribution, as well as the evolution of the size and number of sulfur clusters in the simulations. The relevant conclusions indicate that confinement effect is in favor of the dissolution of elemental sulfur in H2S. Our study is critical to construct the theoretical basis for sulfur dissolution or deposition in the development of high-sulfur carbonate gas reservoirs.
{"title":"A molecular simulation study on solubility of elemental sulfur in hydrogen sulfide confined in calcite nanopores","authors":"Yuan Wei , Xuan Li , Shuangli Yue , Xue Wu , Xiangyu Huo","doi":"10.1016/j.fluid.2025.114656","DOIUrl":"10.1016/j.fluid.2025.114656","url":null,"abstract":"<div><div>Knowledge of the solubility evolution of elemental sulfur in natural gas is the theoretical basis for preventing sulfur deposition in high-sulfur carbonate gas reservoir developments. In addition to temperature, pressure and composition, confinement nanopore throats also affects the sulfur solubility. All-atom equilibrium molecular dynamic simulations are conducted to study the solubility of elemental sulfur in H<sub>2</sub>S confined in calcite slit nanopores under reservoir conditions. The sulfur solubility in the calcite pore reduces with slit aperture, and it is dramatically larger than that in the unconfined bulk system. The molecular mechanism of the over-solubility of sulfur is identified as the adsorption-driven effect of solute molecules, which is revealed through analysis on the interaction between the solute/solvent and calcite surface, the particle structure distribution, as well as the evolution of the size and number of sulfur clusters in the simulations. The relevant conclusions indicate that confinement effect is in favor of the dissolution of elemental sulfur in H<sub>2</sub>S. Our study is critical to construct the theoretical basis for sulfur dissolution or deposition in the development of high-sulfur carbonate gas reservoirs.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114656"},"PeriodicalIF":2.7,"publicationDate":"2025-12-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-15DOI: 10.1016/j.fluid.2025.114654
Khang Quang Bui, Gabriel D. Barbosa, Dimitrios V. Papavassiliou, Alberto Striolo
Towards implementing modern geo-energy applications such as geological hydrogen storage, it is imperative to quantify the behavior of aqueous electrolyte systems confined in narrow pores exposed to high pressure and temperature conditions. This study systematically compares the properties of aqueous NaCl solutions in kaolinite nanopores as predicted when three widely used NaCl forcefields are implemented, namely the Smith-Dang (SD), the Joung-Cheatham (JC), and the Horinek et al. (HR). Nanoconfinement is found to dictate fluid distribution and mobility within the pores. Significant differences due to the implemented forcefields emerge in ion pairing, local water structure, and hydrogen bond network. Vibrational spectra show pronounced forcefield sensitivity as well, both in bulk and in confinement; confinement amplifies these differences substantially. Consistent with experiments, all models predict salting-out effects in the bulk; the effects predicted in confinement are weaker, suggesting that increasing salt content may not be as effective at reducing H2 solubility in confined water as it is in bulk systems. These results should be considered when geo-energy operations are being designed, for example geological hydrogen storage.
为了实现地质储氢等现代地能应用，必须量化高压和高温条件下狭窄孔隙中的水电解质体系的行为。在Smith-Dang （SD）、jung - cheatham （JC）和Horinek et al. （HR）三种常用的NaCl力场作用下，本研究系统地比较了高岭石纳米孔中NaCl水溶液的性质。发现纳米约束决定了孔隙内的流体分布和流动性。在离子对、局部水结构和氢键网络中，由于实施力场的不同而产生了显著的差异。振动谱也显示出明显的力场敏感性，无论是在块状还是在约束中；禁闭大大放大了这些差异。与实验结果一致，所有的模型都预测了整体的盐析效应；约束条件下预测的效应较弱，这表明增加盐含量在降低H2在约束水中的溶解度方面可能不如在散装体系中有效。在设计地能操作时，例如地质储氢，应该考虑这些结果。
{"title":"Weak salting-out of H2 gas from aqueous NaCl solutions confined in kaolinite nanopores","authors":"Khang Quang Bui, Gabriel D. Barbosa, Dimitrios V. Papavassiliou, Alberto Striolo","doi":"10.1016/j.fluid.2025.114654","DOIUrl":"10.1016/j.fluid.2025.114654","url":null,"abstract":"<div><div>Towards implementing modern geo-energy applications such as geological hydrogen storage, it is imperative to quantify the behavior of aqueous electrolyte systems confined in narrow pores exposed to high pressure and temperature conditions. This study systematically compares the properties of aqueous NaCl solutions in kaolinite nanopores as predicted when three widely used NaCl forcefields are implemented, namely the Smith-Dang (SD), the Joung-Cheatham (JC), and the Horinek et al. (HR). Nanoconfinement is found to dictate fluid distribution and mobility within the pores. Significant differences due to the implemented forcefields emerge in ion pairing, local water structure, and hydrogen bond network. Vibrational spectra show pronounced forcefield sensitivity as well, both in bulk and in confinement; confinement amplifies these differences substantially. Consistent with experiments, all models predict salting-out effects in the bulk; the effects predicted in confinement are weaker, suggesting that increasing salt content may not be as effective at reducing H<sub>2</sub> solubility in confined water as it is in bulk systems. These results should be considered when geo-energy operations are being designed, for example geological hydrogen storage.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114654"},"PeriodicalIF":2.7,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.fluid.2025.114652
Hiroaki Matsukawa , Ryota Suzuki , Katsuto Otake
Phase diagrams of CO2/cosolvent/polymer systems are critical for polymer processing applications, yet most studies have focused on pressure–temperature diagrams, leaving pressure–composition (Px) diagrams less understood. In particular, the influence of cosolvent species on ternary Px phase behavior and its molecular-level origin has not been systematically investigated. This study examined the phase behavior of CO2/ethanol (EtOH) or dimethyl sulfoxide (DMSO)/poly(ethylene glycol) (PEG) ternary systems to evaluate the effect of cosolvent species on the phase diagram. Measurements were performed using a synthetic method combined with laser displacement and turbidity detection. Bubble points (vapor–liquid (VL) phase separation) were determined from piston displacement changes, and cloud points (liquid–liquid (LL) phase separation) were identified from turbidity variations. Phase boundaries were obtained for CO2 mass fractions of 0.148–0.680 while varying the cosolvent/PEG mass ratio. The polymer did not participate in VL phase separation, reflecting the affinity between CO2 and the cosolvent. By contrast, LL phase separation required consideration of the mutual affinities among all three components. To support this interpretation, the free volume fraction difference (Δf) estimated from the Sanchez–Lacombe equation and the dipole and quadrupole moments obtained from quantum chemical calculations were analyzed. The Δf values explained the cosolvent-dependent shifts in the LL line, whereas the μ and Q values clarified the order of mutual solubility (EtOH > DMSO > Tol) in agreement with experimental observations. These findings provide a more comprehensive understanding of the CO2/cosolvent/polymer phase behavior and facilitate the prediction of phase diagrams.
{"title":"Phase behavior of CO2/Organic Solvent/Poly(ethylene glycol) ternary systems","authors":"Hiroaki Matsukawa , Ryota Suzuki , Katsuto Otake","doi":"10.1016/j.fluid.2025.114652","DOIUrl":"10.1016/j.fluid.2025.114652","url":null,"abstract":"<div><div>Phase diagrams of CO<sub>2</sub>/cosolvent/polymer systems are critical for polymer processing applications, yet most studies have focused on pressure–temperature diagrams, leaving pressure–composition (<em>Px</em>) diagrams less understood. In particular, the influence of cosolvent species on ternary <em>Px</em> phase behavior and its molecular-level origin has not been systematically investigated. This study examined the phase behavior of CO<sub>2</sub>/ethanol (EtOH) or dimethyl sulfoxide (DMSO)/poly(ethylene glycol) (PEG) ternary systems to evaluate the effect of cosolvent species on the phase diagram. Measurements were performed using a synthetic method combined with laser displacement and turbidity detection. Bubble points (vapor–liquid (VL) phase separation) were determined from piston displacement changes, and cloud points (liquid–liquid (LL) phase separation) were identified from turbidity variations. Phase boundaries were obtained for CO<sub>2</sub> mass fractions of 0.148–0.680 while varying the cosolvent/PEG mass ratio. The polymer did not participate in VL phase separation, reflecting the affinity between CO<sub>2</sub> and the cosolvent. By contrast, LL phase separation required consideration of the mutual affinities among all three components. To support this interpretation, the free volume fraction difference (<em>Δf</em>) estimated from the Sanchez–Lacombe equation and the dipole and quadrupole moments obtained from quantum chemical calculations were analyzed. The <em>Δf</em> values explained the cosolvent-dependent shifts in the LL line, whereas the <em>μ</em> and <em>Q</em> values clarified the order of mutual solubility (EtOH > DMSO > Tol) in agreement with experimental observations. These findings provide a more comprehensive understanding of the CO<sub>2</sub>/cosolvent/polymer phase behavior and facilitate the prediction of phase diagrams.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114652"},"PeriodicalIF":2.7,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145753854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.fluid.2025.114653
Juan Heringer , Michiel Wapperom , Catinca Secuianu , Denis Voskov , Dan Vladimir Nichita
Phase equilibrium calculations play an important role in a wide variety of applications in chemical and petroleum engineering. In this work, we focus on CO2-hydrocarbon mixtures, with applications ranging from enhanced oil recovery processes to CO2 storage. In compositional reservoir simulation, both robustness and efficiency are of utmost importance. The conventional approach for multiphase equilibrium consists of a sequence of phase stability and flash calculations. At each level of the stepwise process, stability testing is performed starting from several initial guesses; therefore, reducing the number of stability calls and using judiciously the information from stability to initialize a phase split are key points in developing an efficient stability-flash algorithm. Two new initialization strategies for multiphase flash calculations are proposed. The first one (improved stepwise initialization) follows the conventional procedure, but uses additional initial guesses. In the second one (improved multiple initialization), a three-phase split is initiated if at least three minima of the tangent plane distance (TPD) function are detected by stability analysis of feed composition. Both proposed methods are using all information from phase stability testing at each stage. Unlike in previous formulations, compositions at all minima of the TPD function, including trivial and positive TPDs are used to generate initial equilibrium constants. Highly robust routines are used, based on successive substitution iterations (SSI) in early iteration stages, followed by Newton iterations with modified Cholesky factorization and line search, in both stability and flash calculations. The proposed methods are tested and compared with the conventional procedure for several benchmark mixtures from the literature, containing hydrocarbon components and CO2. Phase diagrams are constructed in the P-Z plane, focusing on the number of stationary points of the TPD functions found in each step of the multiphase stability-flash algorithm and on how they must be efficiently used in initialization. For all the test mixtures, in the proposed stability-flash strategy, the number of calls of the stability and flash routines and the number of iterations in flash calculations are significantly reduced as compared to previous approaches, recommending the new approach as a useful tool in compositional simulation.
{"title":"New initialization procedures from phase stability testing in three-phase flash calculations for CO2-hydrocarbon mixtures","authors":"Juan Heringer , Michiel Wapperom , Catinca Secuianu , Denis Voskov , Dan Vladimir Nichita","doi":"10.1016/j.fluid.2025.114653","DOIUrl":"10.1016/j.fluid.2025.114653","url":null,"abstract":"<div><div>Phase equilibrium calculations play an important role in a wide variety of applications in chemical and petroleum engineering. In this work, we focus on CO<sub>2</sub>-hydrocarbon mixtures, with applications ranging from enhanced oil recovery processes to CO<sub>2</sub> storage. In compositional reservoir simulation, both robustness and efficiency are of utmost importance. The conventional approach for multiphase equilibrium consists of a sequence of phase stability and flash calculations. At each level of the stepwise process, stability testing is performed starting from several initial guesses; therefore, reducing the number of stability calls and using judiciously the information from stability to initialize a phase split are key points in developing an efficient stability-flash algorithm. Two new initialization strategies for multiphase flash calculations are proposed. The first one (improved stepwise initialization) follows the conventional procedure, but uses additional initial guesses. In the second one (improved multiple initialization), a three-phase split is initiated if at least three minima of the tangent plane distance (TPD) function are detected by stability analysis of feed composition. Both proposed methods are using all information from phase stability testing at each stage. Unlike in previous formulations, compositions at all minima of the TPD function, including trivial and positive TPDs are used to generate initial equilibrium constants. Highly robust routines are used, based on successive substitution iterations (SSI) in early iteration stages, followed by Newton iterations with modified Cholesky factorization and line search, in both stability and flash calculations. The proposed methods are tested and compared with the conventional procedure for several benchmark mixtures from the literature, containing hydrocarbon components and CO<sub>2</sub>. Phase diagrams are constructed in the <em>P</em>-<em>Z</em> plane, focusing on the number of stationary points of the TPD functions found in each step of the multiphase stability-flash algorithm and on how they must be efficiently used in initialization. For all the test mixtures, in the proposed stability-flash strategy, the number of calls of the stability and flash routines and the number of iterations in flash calculations are significantly reduced as compared to previous approaches, recommending the new approach as a useful tool in compositional simulation.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"604 ","pages":"Article 114653"},"PeriodicalIF":2.7,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-03DOI: 10.1016/j.fluid.2025.114651
Yi Zhang , Xiaowei Cheng , Shiyu Sun , Baoshu Liu , Hua Sun
The solubility of active pharmaceutical ingredients is vital throughout the drug design, development processes and manufacture. However, solubility prediction remains a challenging task in the pharmaceutical field. Therefore, BCS class II drugs solubility prediction model was developed on the basis of the machine learning algorithms and molecular descriptors through Bayesian Optimization, cosine similarity and sparse principal component analyses, revealing XGBoost model exhibited the better accuracy and suitability. Besides, the generalization of XGBoost model was confirmed by the solubility data prediction in the uncommon solvents and unseen solutes. Influences of molecular descriptors on the predicted solubility data were evaluated through Shapley Additive Explanations analysis, exposing the temperature exhibited a positive effect on the predicted solubility and the double bonds number of the solvent molecule presented a negative effect on the predicted solubility data. The various molecular descriptor contributions to the solubility prediction of XGBoost model were analyzed through feature importance, exposing the molecular descriptor contributions followed the order: Chi0 > SMR_VSA1 > MolMR > ExactMolWt > T > NumValenceElectrons > fr_C_O. In addition, it revealed the studied molecular descriptors must synergistically contribute to the solubility data prediction of XGBoost model according to prediction results comparison of simple and original XGBoost models.
{"title":"Solubility prediction of BCS class II drugs through combining machine learning and molecular descriptor","authors":"Yi Zhang , Xiaowei Cheng , Shiyu Sun , Baoshu Liu , Hua Sun","doi":"10.1016/j.fluid.2025.114651","DOIUrl":"10.1016/j.fluid.2025.114651","url":null,"abstract":"<div><div>The solubility of active pharmaceutical ingredients is vital throughout the drug design, development processes and manufacture. However, solubility prediction remains a challenging task in the pharmaceutical field. Therefore, BCS class II drugs solubility prediction model was developed on the basis of the machine learning algorithms and molecular descriptors through Bayesian Optimization, cosine similarity and sparse principal component analyses, revealing XGBoost model exhibited the better accuracy and suitability. Besides, the generalization of XGBoost model was confirmed by the solubility data prediction in the uncommon solvents and unseen solutes. Influences of molecular descriptors on the predicted solubility data were evaluated through Shapley Additive Explanations analysis, exposing the temperature exhibited a positive effect on the predicted solubility and the double bonds number of the solvent molecule presented a negative effect on the predicted solubility data. The various molecular descriptor contributions to the solubility prediction of XGBoost model were analyzed through feature importance, exposing the molecular descriptor contributions followed the order: <em>Chi0</em> > <em>SMR_VSA1</em> > <em>MolMR</em> > <em>ExactMolWt</em> > <em>T</em> > <em>NumValenceElectrons</em> > <em>fr_C_O</em>. In addition, it revealed the studied molecular descriptors must synergistically contribute to the solubility data prediction of XGBoost model according to prediction results comparison of simple and original XGBoost models.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"603 ","pages":"Article 114651"},"PeriodicalIF":2.7,"publicationDate":"2025-12-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-02DOI: 10.1016/j.fluid.2025.114650
Adina Werner, Jongmin Kim, Fabian Mauss
Excess volumes can be calculated generally via equations of state. In this work, the excess volumes are obtained using the UNIQUAC model with two approaches of a temperature- and pressure-dependent binary interaction parameter. The pressure dependency is required as the excess volume is derived from the pressure dependency of the excess free enthalpy. Both UNIQUAC approaches are successfully able to predict the vapor-liquid equilibrium as well as the excess volume of methanol-water mixtures over a temperature range between 288.15–473 K and a pressure range between 0.1519–134 bar using a single optimized parameter set.
{"title":"Excess volumes calculated from UNIQUAC model using the example of methanol - water mixtures","authors":"Adina Werner, Jongmin Kim, Fabian Mauss","doi":"10.1016/j.fluid.2025.114650","DOIUrl":"10.1016/j.fluid.2025.114650","url":null,"abstract":"<div><div>Excess volumes can be calculated generally via equations of state. In this work, the excess volumes are obtained using the UNIQUAC model with two approaches of a temperature- and pressure-dependent binary interaction parameter. The pressure dependency is required as the excess volume is derived from the pressure dependency of the excess free enthalpy. Both UNIQUAC approaches are successfully able to predict the vapor-liquid equilibrium as well as the excess volume of methanol-water mixtures over a temperature range between 288.15–473 K and a pressure range between 0.1519–134 bar using a single optimized parameter set.</div></div>","PeriodicalId":12170,"journal":{"name":"Fluid Phase Equilibria","volume":"603 ","pages":"Article 114650"},"PeriodicalIF":2.7,"publicationDate":"2025-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145682426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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