Abstract Experimental density and refractive index data were measured for six ionic liquids (ILs) (three hexafluorophosphate-based: [Bmim+][PF6–], [Hmim+][PF6–], [Omim+][PF6–]; and three bis(trifluoromethylsulfonyl)imide-based: [Emim+][NTf2–], [Hmim+][NTf2–], [Omim+][NTf2–]) and their binary mixtures with rac-2-pentanol, vinyl butyrate, rac-2-pentyl butyrate, and butyric acid over the temperature range of 293.15–343.15 K at 0.1 MPa. These systems are relevant due to the role of S-2-pentanol as a chiral intermediate in the synthesis of anti-Alzheimer drugs targeting β-amyloid pathways, and its production by enzymatic kinetic resolution of rac-2-pentanol using lipase-catalyzed transesterification with vinyl esters, which requires accurate thermophysical data in IL media. The experimental data were analyzed through excess molar volumes, apparent and partial molar properties, and infinite dilution functions to elucidate intermolecular interactions and packing effects. Temperature- and composition-dependent polynomial correlations were applied, showing excellent agreement with experimental values. The refractive index data were modeled using mixing rules, with the Wiener model providing the best performance. Deviations in volumetric and optical properties were interpreted in terms of molecular size, polarity, and polarizability, highlighting the influence of the IL structure on mixture nonideality. Overall, this work provides a consistent thermophysical data set and reliable correlations for IL-based mixtures, supporting their characterization and potential application in biocatalytic synthesis relevant to anti-Alzheimer drug production.
Abstract Deep eutectic solvents (DESs) were prepared by mixing choline chloride (ChCl) and thymol (Thy) at molar ratios ranging from 1:1 to 1:10. Among the prepared mixtures, ChCl:Thy ratios of 1:4 to 1:10 formed homogeneous liquids and remained stable for more than 744 h. These seven DESs were characterized using Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, and thermogravimetric analysis (TGA) to evaluate their structural characteristics and thermal stability. FTIR and NMR analyses confirmed the formation of strong hydrogen-bonding interactions, particularly between chloride ions and the hydroxyl group of thymol (Cl···H–O), which disrupt the crystal lattices of the parent components and facilitate eutectic formation. The decomposition temperature decreased from 239.9 °C for ChCl:4Thy to 142.3 °C for ChCl:6Thy with increasing thymol content. Compared with pure ChCl (319.2 °C) and thymol (101.9 °C), the DESs exhibited modified thermal stability due to the newly established hydrogen-bonding network. Furthermore, COSMO-RS-derived sigma profiles and sigma potentials supported the strong Cl···H–O interactions and confirmed the favorable formation and stability of ChCl:Thy DESs over the 1:4 to 1:10 molar-ratio range.
Abstract Adding NaCO3 or K2CO3 to a binary mixture ethanol/water or isopropanol/water triggers a liquid–liquid phase split at ambient conditions. One of the phases is rich in alcohol, and the other is rich in water. This phenomenon could be potentially used in the development of low-carbon separation technologies for alcohols produced from biomass fermentation. In this study, the phase behavior of the following mixtures was investigated at ambient conditions: ethanol/water/sodium carbonate (Na2CO3), ethanol/water/potassium carbonate (K2CO3), isopropanol/water/Na2CO3, and isopropanol/water/K2CO3. To do so, the entire liquid–liquid (LL) envelope was experimentally mapped by detecting the liquid ↔ liquid/liquid (L ↔ LL) and liquid/liquid ↔ solid/liquid/liquid (LL ↔ SLL) boundaries. LL tie lines were also measured. The measured LL boundaries and tie lines were used for locating the plait point using a well-known methodology. The quality of the data was assessed by using graphical methods that allowed the detection of outliers. The internal consistency of the measured tie lines was verified by comparing the measured data with pure predictions from the electrolyte version of the UNIQUAC model. The internal consistency of the measured L ↔ LL boundary was assessed by comparison with predictions from an empirical model developed by fitting the measured LL tie lines.
Abstract Adjusting the critical point of CO2 by adding propane is an effective method to enhance the performance of the supercritical CO2 Brayton cycle under high-temperature conditions. This study measured the isobaric specific heat capacity of CO2, propane, and their mixtures within the temperature range of 323–473 K and pressure range of 8–12 MPa using a flow calorimeter. We optimized the parameters of the GERG-2008 model for the CO2/propane mixture system. Results indicate that the isobaric specific heat capacity of CO2 and propane, as well as their mixtures, exhibits sensitivity to temperature and pressure variations in the pseudocritical region, with the sensitivity becoming increasingly gradual when moving away from this region. The isobaric specific heat capacity of the mixture increases with rising propane content. The average absolute relative deviation (AARD) between experimental values and GERG-2008 model calculations for pure CO2, propane, and mixtures was 0.79%, 0.86%, and 1.25%, respectively. The GERG-2008 model, optimized using literature and experimental data, significantly improved the calculation accuracy of isobaric specific heat capacity for CO2/propane mixtures, reducing the AARD to 0.93%.
Abstract In a recent article titled “Solubility Determination and Correlation of 2-Methyl-6-propionylnaphthalene in Pure Solvents and Binary Solvent Systems (Water + Methanol/Ethanol/n-Propanol) from 278.15 to 318.15 K” published in this journal, Li et al. reported the solubility behavior of 2-methyl-6-propionylnaphthalene (2,6-MPN) in ten pure solvents and three binary mixed solvents, and conducted a correlation analysis between the experimental solubility data and seven thermodynamic models. While their experimental work provides fundamental data for the crystallization of 2,6-MPN, significant inaccuracies are identified in the fitting parameters of the modified Apelblat equation and the λh equation. These inaccurate parameters lead to substantial deviations between calculated and experimental solubilities. This work systematically verifies the errors, analyzes their origins, and provides optimization suggestions, aiming to ensure the reliability of thermodynamic data for 2,6-MPN crystallization process design and solvent selection.
Abstract This investigation briefs the thermophysical properties of amino acids (l-arginine and l-threonine) in water and in aqueous 1-butyl-3-methylimidazolium chloride solutions (0.05, 0.10, and 0.15 mol kg–1) over the temperature span 293.15 K–318.15 K at ambient pressure (0.1 MPa). The estimated properties were analyzed to attribute the various intermolecular interactions prevailing in the systems. The inferred density data was utilized towards evaluation of apparent molar volume (Vϕ), limiting apparent molar expansibility (Eϕo), limiting apparent molar volume (Vϕo), limiting apparent molar volume of transfer (ΔtrVϕo), and Hepler’s constant (∂Eϕo∂T)P. Further, via data of sound speed, apparent molar isentropic compression (Kϕ,s), limiting apparent molar isentropic compression (Kϕ,so), limiting apparent molar isentropic compression of transfer (ΔtrKϕ,so), and hydration number were inferred. Also, through viscosity data and by the usage of the Jones–Dole equation, the parameters mainly viscosity B-coefficients, temperature derivative of B ( dBdT), and activation parameters of viscous flow (Δμ10, Δμ20, ΔH20, and TΔS20) were inferred. Moreover, through scrutinization of Hepler’s constant and temperature derivative of B, we assessed that both amino acids function as chaotropes in selected solvents (water and aqueous ionic liquid). UV–visible spectroscopic investigations additionally uphold the predominance of hydrophilic–hydrophilic interactions in the considered systems.
Abstract The solubility of quizalofop-p-ethyl in four aqueous binary mixtures, namely n-propanol–water, isopropanol–water, N,N-dimethylformamide (DMF)–water, and N,N-dimethylacetamide (DMAC)–water, was determined using the laser monitoring method over the temperature range from 278.15 to 318.15 K. In all systems, the solubility increased monotonically with increasing temperature and organic cosolvent mole fraction. The experimental solubility data were correlated using the modified Apelblat, the Van’t Hoff–Jouyban–Acree model, and the Wilson models. The correlation performance of these models was evaluated using the relative average deviation (RAD) and root-mean-square deviation (RMSD). Based on the deviation metrics, the modified Apelblat model exhibited the lowest fitting deviations for the present QPE solubility data set under the current fitting framework, with calculated values in good agreement with the experimental data. In addition, Hansen solubility parameter (HSP) analysis was used to qualitatively evaluate QPE–solvent compatibility, suggesting that the observed solvent effects are related to the combined matching of dispersion, polar, and hydrogen-bonding parameters.
Abstract This study presents a comprehensive investigation of the molecular interactions in the binary system of dimethyl carbonate and adiponitrile (ADN) by integrating thermodynamic measurements, spectroscopic analyses, and molecular dynamics (MD) simulations. Experimental data on density, speed of sound, and refractive index were collected across a temperature range of 293.15 K–318.15 K, revealing significant nonideal mixing behavior, including negative excess molar volumes and positive deviations in speed of sound and refractive index, which intensify with rising temperature due to enhanced intermolecular interactions. MD simulations and spectroscopic evidence (Fourier transform infrared and 1H NMR) confirm the formation of weak C–H···O and C–H···N hydrogen-bond-like contacts, providing a molecular-level explanation for the observed macroscopic properties. These findings underscore the role of specific dipole–dipole and charge-transfer effects in governing the system’s behavior, offering valuable insights for applications in solvent design and molecular engineering.
Abstract In this study, densities, viscosities, and refractive indexes of unsaturated ternary systems MCl+PEG 4000+H2O (M = Li, Na, K) and MgCl2+PEG 4000+H2O were measured at 298.15 K. Additionally, for the latter system, solubility was measured at the same temperature. The Pitzer model was successfully used to fit the experimental data obtained for transport properties and solubilities, except for the viscosities of systems containing NaCl and KCl, which were best represented by Othmer’s rule. The refractive indices were well fitted to the model of Wang et al. Both density and refractive index increase progressively with increasing LiCl and PEG 4000 concentrations, while viscosity increases exponentially. The solubility decreases with increasing PEG 4000 concentration, following a trend similar to the common-ion effect. The polymer was considered a neutral species in the Pitzer model. Analysis of the solubility of the MgCl2+PEG 4000+H2O system and solubility values reported in the literature for the MCl+PEG 4000+H2O systems at 298.15 K indicates that, in an extractive crystallization process using PEG 4000, LiCl would remain in solution, while NaCl, KCl, and MgCl2 would crystallize. These results are useful in the design and simulation of brine processing and alternative separation processes for lithium extraction.
Abstract In this work, we developed a model capable of representing experimental hydrate-phase equilibria data for mixtures containing hexadecane in pure water and in ethanol–water solutions, yielding an average absolute percentage deviation (AAPD) of 0.6% and a maximum absolute percentage deviation (MAPD) of 1.8%. Experimental determinations of the hydrate phase equilibria data of mixtures containing hexadecane with and without the presence of a thermodynamic inhibitor (ethanol) were carried out and represented with the proposed model. The nonvisual isochoric method by pressure search was used to determine hydrate phase equilibrium data over the temperature ranges of (269.4 to 277.7) K and pressure ranges of (1.3 to 3.1) MPa at a fixed hexadecane mass fraction composition (wC16H34 = 0.1) and several ethanol mass fractions (wC2H6O = 0.05, 0.10, 0.15). Uncertainty analysis was performed, yielding combined uncertainties of 0.14 K and 0.02 MPa for temperature and pressure, respectively, and a relative standard uncertainty of 0.0016 for mass fraction. Prior to the measurements, the viability of the experimental technique was assessed by comparing international literature (pure CO2 hydrate phase equilibrium data) with data obtained using our equipment, thus showing good agreement. A thermodynamic consistency test was performed to verify the reliability of the experimental data involving ethanol.
Abstract The growing dependence on fossil fuels has intensified greenhouse gas emissions, driving interest in renewable alternatives such as biodiesel. Despite its advantages, biodiesel faces limitations due to higher viscosity, lower oxidative stability, and variability in quality when compared to diesel. A promising strategy to mitigate these challenges involves blending biodiesel with short-chain alcohols, which can enhance fuel properties. In this study, experimental evaluations were conducted on blends of 1-propanol and biodiesel derived from waste cooking oil. Key fuel properties were analyzed, including density, viscosity, flash point, and distillation behavior. The addition of 1-propanol consistently decreased density and viscosity, a result attributed to structural differences between esters and alcohols. Blends with intermediate volumetric fractions (0.4–0.8) satisfied ASTM D975 specifications, indicating strong potential for practical applications. However, significant reductions in flash point were observed, emphasizing critical safety considerations for storage and handling. Correlative models demonstrated excellent agreement for density (MAPD < 0.1%) and satisfactory accuracy for viscosity. Predictive models (RAC, DSV, MCH, and NRR) estimated density with MAPDs below 2%, proving reliable for preliminary fuel screening and simulations. Additionally, the Grunberg–Nissan interaction parameter improved viscosity predictions, reducing deviations to below 1.2%. These results provide valuable insights for fuel formulation and process optimization.
Abstract Oxalyl dihydrazide (ODH) is a polymorphic organic compound, and distinct ODH polymorphs possess disparate physicochemical properties, including melting point, solubility, and dissolution kinetics. Under atmospheric pressure, the dynamic method was applied to obtain solid–liquid phase equilibrium information on α-ODH within the temperature range of 293.15–353.15 K. Twelve pure solvents were selected for the tests, namely, water, ethanol, acetic acid, dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylacetamide (DMAC), N,N-diethylformamide (DEF), N,N-dimethylformamide (DMF), 1,3-dimethyl-2-imidazolidinone (DMI), hexamethylphosphoramide (HMPA), and formamide. Experimental results indicated that the solubility of α-ODH monotonically increased with the increase in temperature in all tested solvents. Three thermodynamic models (van’t Hoff equation, Yaws model, and the modified Apelblat equation) were employed to correlate the measured solubility data. In addition, the dissolution thermodynamic properties (Gibbs free energy, entropy, and enthalpy) of α-ODH in the tested solvents were calculated based on the experimental solubility data and the van’t Hoff equation. Moreover, Hirshfeld surface analysis was implemented to characterize dominant intermolecular contacts inside the α-ODH crystal lattice. The acquired solubility data offers reliable fundamental support for industrial crystallization optimization of α-ODH.
Abstract Understanding drug–amino acid interactions in aqueous solution is crucial for predicting physicochemical behavior relevant to drug formulation and biomolecular recognition. This work examines the temperature-dependent interactions of Cytidine (CYTIDINE) with l-valine and l-alanine in water (293.15–308.15 K) using integrated thermodynamic measurements and computational analysis. The results indicate that solute–solvent interactions dominate over solute–solute associations in both ternary systems, with CYTIDINE exhibiting structure-breaking behavior. Interaction strength is consistently greater in the CYTIDINE–l-valine system than in CYTIDINE–l-alanine, attributed to enhanced hydrophobic contributions from the bulkier side chain of l-valine. Gibbs free energy-derived binding affinity and noncovalent interaction analysis from optimized geometries support the experimental observations. This study establishes a direct correlation between temperature-dependent macroscopic thermodynamic behavior and molecular-level interaction patterns in nucleoside–amino acid aqueous systems, providing new insight into hydrophilic–hydrophobic balance relevant to biopharmaceutical solution chemistry.
The densities and viscosities of the three amine-based deep eutectic solvents (DESs), i.e., [EmimCl]-[MEA], [BmimCl]-[MEA], and [HmimCl]-[MEA], mixed with ethanol (EtOH), were measured from 288.15 to 323.15 K, and their enthalpies of mixing were determined at 298.15 and 308.15 K. Negative excess molar volumes across the entire compositional range indicate significant volume contraction and enhanced molecular packing, and their temperature dependence suggests the dominance of packing effects over hydrogen-bonding. Viscosity deviations show a characteristic U-shaped composition dependence, reflecting disruption of the original DES hydrogen-bond network by EtOH. The enthalpy of mixing changes from positive to negative as the DES composition increases, revealing strengthened DES-EtOH interactions. The distinct composition-dependent trends observed for these three (DES + EtOH) systems indicate that variations in alkyl chain length modulate molecular packing and interaction strength, resulting in nonuniform ordering patterns across thermophysical properties. Compared to water, which strongly restructures the DES hydrogen-bond network and produces significant exothermic mixing effects, EtOH exerts a milder structural and thermodynamic impact. This work provides reliable thermodynamic data and mechanistic insight for the design and application of amine-based DESs.
Abstract High-value, low-volume solutes are characteristic of bioprocessing waste residues and are typically the focus of separation process design; the equilibria of the waxy bulk components are often overlooked despite their ubiquity. In this work, a low-volume method for measuring (solid–)liquid–liquid equilibrium data is validated and applied to generate new data for the ternary system acetonitrile + n-heptane + palmitic acid between 298 and 313 K. Results show the fatty acid reports overwhelmingly to the alkane phase, highlighting acetonitrile’s potential as a selective solvent for polar solutes in waxy residues. Temperature had a small effect on palmitic acid’s distribution between phases but a significant effect on the liquid operating region, with solubility decreasing rapidly at lower temperatures. The data were modeled predictively with the new modified UNIFAC 2.0 model and correlated with NRTL. Modified UNIFAC 2.0 failed to quantitatively capture the experimental equilibria, while NRTL showed excellent agreement across all temperatures despite parameters being fitted only to independent sub-binary data, and ternary data at a single temperature. These results reassert the importance of quantifying all equilibria present in a system for effective separation process design and establish a low-volume methodology for generating such data in future work on similar systems.
Abstract Wu et al. have submitted a Commentary identifying discrepancies between the fitting parameters reported in the Supporting Information of our paper and the experimental solubility data presented in the main text.
Abstract This study investigates the crystallization behavior of Sr(NO3)2 in aqueous solution by integrating classical nucleation theory and the Apelblat equation. We experimentally characterize the metastable zone width as a function of saturation temperature, cooling rate, and stirring rate. Based on classical nucleation theory, we establish a quantitative thermodynamic-kinetic coupling model that directly relates the solubility temperature coefficient to metastable zone width. Phase-specific coupling models are further developed for the low-temperature β-phase and high-temperature α-phase regions, respectively, with high determination coefficients. Two distinct solubility regimes are identified: β-phase solubility increases significantly with T0 in the low-temperature range (278.15–298.15 K), while α-phase solubility growth slows in the high-temperature range (303.15–363.15 K), with a phase transition critical point at 301.54 K. Fitting metastable zone width data to the classical 3D nucleation model reveals that the nucleation rate constant A increases and the solid–liquid interfacial energy parameter B decreases with rising T0, indicating enhanced nucleation driving force and reduced energy barriers collectively narrow the metastable zone width. These findings fill the long-standing data gap in the nucleation kinetic parameters of Sr(NO3)2 aqueous crystallization across the peritectic transition region, and provide theoretical guidance for optimizing cooling rate and temperature staging regulation in the directional growth of Sr(NO3)2 crystals.
Abstract Investigation of the relevant multitemperature phase equilibrium data is of guiding importance for the recycling and utilization of rich-boron brine resources. In this work, the solid–liquid phase equilibria of the K2B4O7–KHCO3–Na2B4O7–NaHCO3–H2O quaternary system at 288.2 and 308.2 K were investigated using the isothermal dissolution equilibrium method. The results demonstrate that the system exhibits Type I hydrate behavior at both temperatures, with each phase diagram featuring two invariant points. The equilibrium solid phases at invariant points are NaHCO3 + Na2B4O7·10H2O + K2B4O7·4H2O and NaHCO3 + K2B4O7·4H2O + KHCO3, respectively. Each phase diagram consists of five solubility equilibrium curves and four crystallization regions corresponding to the solid phases: Na2B4O7·10H2O, K2B4O7·4H2O, KHCO3, and NaHCO3. Comparative analysis of the crystallization regions at the two temperatures reveals that the region for Na2B4O7·10H2O shrinks with increasing temperature, whereas those for NaHCO3, K2B4O7·4H2O, and KHCO3 expand. At both temperatures, the crystallization region of Na2B4O7·10H2O is the largest, followed by that of NaHCO3, while KHCO3 has the smallest region. This trend indicates that KHCO3 has the highest solubility and is therefore the most difficult to crystallize and separate from the saturated solution.
Abstract Recently, Jia and his research team published an academic paper titled “Solubility Behavior of Meglumine Form I in 12 Pure Solvents: Experimental Measurements, Thermodynamic Modeling, And Solvation Mechanism Analysis.” in this journal, correlating the experimental data with three thermodynamic models (modified Apelblat equation, λh equation, and van’t Hoff equation). However, verification indicates that the parameters of the modified Apelblat and van’t Hoff models reported in the original paper are incorrect, leading to significant deviations between the calculated and experimental solubility values, even order-of-magnitude differences in some solvent systems. This commentary first verifies the errors of the original model parameters and quantifies the deviations. The modified Apelblat and van’t Hoff models are then refitted using the original experimental data, obtaining corrected parameters with average relative deviations (ARD) of 1.91% and 2.11%, respectively. The λh model parameters in the original work are relatively reliable and do not require refitting. Additionally, possible causes of the fitting errors in the original study are analyzed, including unspecified adoption of scaled solubility data for model fitting and insufficient decimal places of fitting parameters. The corrected model parameters provided herein can offer reliable thermodynamic data for the crystallization, formulation development, and industrial application of Meglumine Form I and also remind researchers to pay attention to data accuracy in thermodynamic fitting studies.
Ionization constants, K a,H, for N,N-diethylhydroxylamine (DEHA) have been measured under hydrothermal conditions, from 25 to 250 °C at 15 MPa, using the thermally stable colorimetric pH indicator acridine. The measurements were carried out by UV-visible spectroscopy using a high-temperature, high-pressure titanium flow cell with sapphire windows. The use of flow minimized the effects of thermal decomposition because the data could be collected rapidly with short equilibration times. NMR and Raman spectroscopic analysis of the quenched experimental solutions from 250 °C showed that the extent of DEHA decomposition in the experimental solution was minimal at the highest temperature studied. These are the first experimental values for the ionization constant of DEHA above 25 °C that have been reported. The experimental values of pK a,H for DEHA were fitted using the simplified form of the extended van't Hoff equation for an isocoulombic reaction and with Mesmer's "Density" model to generate thermochemical parameters suitable for the EPRI MULTEQ chemical equilibrium model and other similar software used to model water chemistry in nuclear reactor secondary coolant systems and in fossil steam generating systems.
