Journal of Chemical & Engineering Data最新文献

1,3-Propanediol (1,3PD), 2-methyl-1,3-propanediol (2M1,3PD), 1,2-butanediol (1,2BD), 1,3-butanediol (1,3BD), and 1,4-butanediol (1,4BD), and their aqueous solutions, are commonly used as heat transfer fluids. The thermal conductivity (λ) of these substances is a critical physical property. However, limited data are available in the literature, particularly for their aqueous solutions. In this study, λ of the aforementioned aqueous solutions was measured using a transient hot-wire apparatus over the temperature (T) range of 293 to 373 K at ambient pressure close to 0.1 MPa, with an estimated expanded uncertainty of 1.7% (k = 2). The reliability of the experimental setup was validated by using pure water prior to measurements. Empirical correlations were developed to represent λ of both the pure alcohols and their aqueous solutions. For the pure alcohols, the deviation between experimental and correlated values was within 0.5%, while for the aqueous solutions, the deviation was within 3.9%. A brief analysis of structure–property relationships was conducted, suggesting that the nonideality observed in aqueous solutions may be attributed to changes in hydrogen bonding and dipole–dipole interactions caused by structural rearrangement in the solution. The results presented in this work provide valuable data for industrial applications and thermal design involving these aqueous solutions.

Aqueous two-phase systems (ATPS) based on deep eutectic solvents (DES), composed of low-cost, nontoxic materials, enhance the green character of this technique. This study determined solubility curves for ATPS formed by DES (choline chloride and carbohydrates: d-fructose, d-glucose, or sucrose), poly(ethylene glycol) (PEG400) or K₂HPO₄, and water, at different temperatures. Temperature had no significant effect on the solubility curves, suggesting entropy-driven phase separation. The type of carbohydrate used in the DES did not influence separation behavior, indicating that choline chloride is the main species driving demixing. This was supported by solubility curves at varying DES molar ratios, with higher choline chloride content requiring lower concentrations for phase formation. Additionally, K₂HPO₄ required concentrations lower than those of PEG400 to induce phase separation. The partitioning of Cu(II) (1.25 ≤ K ≤ 6.54) and Fe(III) (0.123 ≤ K ≤ 0.153) ions was also investigated. Cu(II) preferentially migrated to the top phase, while Fe(III) remained in the bottom phase. Cu(II)‘s affinity for choline chloride likely reduces its hydration, favoring its transfer to the less aqueous phase. These findings highlight the potential of DES-based ATPS for selective metal ion extraction without additional extractants.

The combustion behavior of fuels or surrogate fuel mixtures can be modeled better if their physical properties are known. This work reports densities, viscosities, and speeds of sound of binary mixtures of undecane with n-alkylbenzenes (ethylbenzene to n-tridecylbenzene). An assessment of mixture densities using jet and diesel fuel specifications shows that some of these mixtures fall within the required range of values. Mixture densities and speeds of sound decreased with increasing temperature and decreasing n-alkylbenzene mole fraction. Mixture viscosities decreased with increases in temperature and the component with lower viscosity, except for some n-butylbenzene systems where smaller viscosities were found in a mixture. Increasing the n-alkylbenzene size up to n-tridecylbenzene produced lower excess molar volumes (V_m^E’s) and excess isentropic compressibilities as well as higher excess speeds of sound. Viscosity deviations were the lowest for the n-hexylbenzene mixtures. A reduction in free volume is likely a contributor to negative V_m^E’s, while a reduction in the attraction of molecules is likely a contributor to the positive V_m^E’s. A comparison of derived properties with those of undecane/n-alkylcyclohexane mixtures revealed similar trends, with the greatest differences occurring for the smallest molecules.

Liquid–liquid equilibrium (LLE) data and phase diagrams for aqueous two-phase systems containing poly(ethylene glycol) (PEG) of different molar weights (1500, 4000, or 6000) g·mol^–1 and potassium sodium tartrate (organic salt) were determined experimentally at different temperatures (293.15, 303.15, and 313.15) K and atmospheric pressure. Effects of temperature, polymer molar weight, and nature of the salt anion on the solubility curves were studied and compared with data from the literature. The results showed that increasing both the molar weight of the polymer and temperature enhances the biphasic area of the systems. The NRTL activity coefficient model was used for correlating the experimental data, presenting satisfactory results (average global deviations between 1.3 and 1.7%).

The substance Tris(2-amino-2-hydroxymethyl-1,3-propanediol, CAS 77-86-1), and its protonated form TrisH⁺, are used in the preparation of “total” pH buffers in artificial seawater media. Here, as part of a series of studies, we present Harned cell measurements of potentials in solutions containing equimolal Tris and TrisHCl (hence TrisH⁺), and also NaCl which is the major constituent of artificial seawater. The methods of preparation of the hydrogen and chloride electrodes are described. The data contribute to the development of a chemical speciation model of the buffer solutions in which solute activity coefficients are calculated using the Pitzer equations. Such a model is required in order to quantify the effects of composition change, convert the total pH to other scales, and to address metrological requirements for traceability. The results are expressed in terms of an acidity function and are compared to previous measurements at 25 °C, including equivalent values for artificial seawater media, and also to calculations using a preliminary model. Agreement is good, and the small differences found between data and model predictions are likely due to offsets in the measured potentials, and uncertainties in some of the Pitzer model parameters and the TrisH⁺ dissociation constant.

The dielectric behavior of R410A is analyzed through Molecular Dynamics (MD) simulations and experimental measurements in both liquid and vapor phases. The simulations are conducted using force fields proposed in the literature for R32 and R125. The simulated results are initially validated against data from the literature for the liquid phase, with deviations below 0.35% and 5.41% for density and the dielectric constant, respectively. To expand the analysis, experimental measurements of the dielectric constant are performed for both liquid and vapor phases under controlled pressure and temperature conditions. The MD simulations performed under the same conditions reproduce the experimental data, with deviations of 2.72% for the liquid phase and 7.83% for the vapor phase. These results support the use of the selected force fields and expand the available dielectric constant data for R410A, providing a basis for evaluating and characterizing other refrigerants with similar electrical properties, including potential low-GWP alternatives.

This article provides precision heat capacity data in the 6–330 K range for crystalline synthetic samples of pyrimidine nucleosides: thymidine (C₁₀H₁₄N₂O₅; CAS Number: 50-89-5; fraction purity: 0.999) and deoxycytidine (C₉H₁₃N₃O₄; CAS Number: 951-77-9; fraction purity: 0.999). The heat capacity of the substances was measured by using vacuum adiabatic calorimetry. No anomalies in heat capacity behaviors indicative of phase transitions were detected within the studied temperature range. The experimental data was mathematically processed, enabling calculation of integral thermodynamic functions (entropy, enthalpy, and reduced Gibbs energy) for thymidine and deoxycytidine in the 0–330 K interval.

Nitrogen is widely used as a process gas, as well as a purge gas in industries. In addition, N₂ also works as a major impurity associated with adsorption technologies for various off-gases and effluent gases. Therefore, understanding the adsorption characteristics of N₂ is of great interest for high-quality gas production. This study examined the adsorption equilibrium and kinetics of three adsorbent pellets, namely activated carbon, alumina-zeolite, and activated alumina, at 293, 308, and 323 K, and pressures up to 1000 kPa. The experimental isotherms were fitted using single-site and dual-site Langmuir models, and the adsorption kinetics were analyzed using experimental uptake curves with a nonisothermal adsorption model with kinetic parameters and diffusional time constant. Activated carbon exhibited a higher adsorption capacity than the other adsorbents. The adsorbents had a fast adsorption rate of N₂, showing only a minor difference among the adsorbents. The adsorption characteristics were compared with those of previously reported adsorbents, such as zeolites, activated carbons, and silica gels, to provide insight and practical guidelines for selecting adsorbents when developing adsorption processes.

Precision data on the heat capacity in the range 6–330 K of crystalline synthetic samples of nucleosides, uridine (C₉H₁₂N₂O₆; CAS Number: 58–96–8; fraction purity: 0.999), and deoxyuridine (C₉H₁₂N₂O₅; CAS Number: 951–78–0; fraction purity: 0.999), are provided herein. This was the first time that the heat capacity of the substances was measured by vacuum adiabatic calorimetry. The heat capacity was found to have no anomalies indicating phase transitions in the tested temperature range. The heat capacity experimental data were used to calculate the entropy, enthalpy, and reduced Gibbs energy for uridine and deoxyuridine in the range 0–330 K. The obtained results are important for understanding the energetics of biochemical processes involving nucleosides, assessing their pharmacological properties and expanding the possibilities of their application.

Given the critical role of hydrofluorocarbons (HFCs) in the refrigeration industry, their recovery is crucial to promoting circular economy strategies and reducing greenhouse gas emissions. In this work, the SAFT-VR Mie equation of state is applied to describe the solubility of R32, R125, and R134a in ionic liquids (ILs) with varying degrees of fluorination, which are proposed as potential absorbents for gas separation. ILs are treated as associating species, with multiple sites accounting for charge delocalization. The model provides an excellent description of density and viscosity, the latter obtained through the Helmholtz scaling theory. In addition, the effect of polarity is explicitly accounted for in the HFCs. As a result, their solubility in ILs is quantitatively reproduced using a single, temperature-independent binary parameter, ensuring a strong predictive capability. Furthermore, the working capacity and competitive selectivity of the components in commercial R410A and R407F blends are predicted, revealing significant differences in performance depending on the solvent composition and fluorination level. Additional properties, such as regeneration enthalpy and viscosity, are also evaluated to identify the most promising ILs for refrigerant recovery. Overall, this study demonstrates the capability of SAFT-VR Mie as a robust molecular-based tool for solvent screening in sustainable HFC separation technologies.