Journal of Chemical & Engineering Data最新文献

This work reports the vapor–liquid equilibria (VLE), liquid viscosity, and surface tension of a potential biofuel mixture formed by diethyl carbonate and 1-butanol. VLE measurements are performed at 50.00, 75.00, and 94.00 kPa, revealing a minimum-boiling azeotrope. The measured VLE data passed the point–point Fredenlund test and are well-correlated using the ϕ−γ approach, where the Wilson model displays the most accurate model for the liquid phase. This model is also incorporated into the Peng–Robinson Stryjek-Vera EoS using the MHV mixing rule to predict VLE data and extend their application over a broad pressure range. The liquid dynamic viscosity is measured at 298.15 K, exhibiting a negative deviation from linear behavior, decreasing as the mole fraction of diethyl carbonate increases. This behavior is predicted by the proposed extension of the scaling viscosity theory based on the EoSs used. The surface tension at 298.15 K showed a positive deviation and exhibited a maximum anisotropy point. The latter results are successfully modeled using the Chunxi model coupled to the reported Wilson model, allowing for the calculation of the relative Gibbs adsorption. The findings provide valuable information to advance the validation of this mixture as a potential biofuel or bio-oxygenate additive for fuels.

The solubility of 2-chlorocinnamic acid in 16 pure organic solvents, including alcohols, esters, ketones, toluene, and acetonitrile, was determined by the gravimetric method at 272.15–321.55 K under 101.3 kPa. Results showed that solubility of 2-chlorocinnamic acid increased with temperature in all solvents. To correlate the experimental data, five thermodynamic models, i.e., the modified Apelblat, Buchowski–Ksiazaczak λh, NRTL, Wilson, and Yaws equations, were employed. Model accuracy was evaluated using average relative deviation (ARD) and root-mean-square deviation (RMSD), and all models provided satisfactory correlations. In addition, electrostatic potential energy surface analysis was carried out to preliminarily assess possible solute–solvent interactions, while density functional theory (DFT) calculations were used to further examine molecular interactions during dissolution. The Kamlet–Abboud–Taft linear solvation energy relationship (KAT-LSER) model was applied to analyze solvent effects. Thermodynamic functions, including enthalpy, entropy, and Gibbs free energy of mixing, were calculated using the Wilson model. The results revealed that the dissolution of 2-chlorocinnamic acid in the studied solvents is an endothermic, entropy-driven, and spontaneous process, indicating favorable solute–solvent interactions and enhanced solubility at higher temperatures.

Based on the characteristics of oilfield waters in the Nanyi Mountain area of western Qaidam basin at subzero temperature, the solid–liquid phase equilibria of ternary systems NH₄Cl–LiCl–H₂O and NH₄Cl–CaCl₂–H₂O at 258.15 K were investigated by using an isothermal solution equilibrium method. The phase diagrams of ternary systems NH₄Cl–LiCl–H₂O and NH₄Cl–CaCl₂–H₂O at 258.15 K were plotted, respectively. The results show that the equilibrium phase diagram of the ternary system NH₄Cl–LiCl–H₂O at 258.15 K has one invariant point, two univariate curves, and two solid-phase crystallization zones (NH₄Cl and LiCl·2H₂O), belonging to hydrate type I. In the equilibrium phase diagram of the ternary system NH₄Cl–CaCl₂–H₂O at 258.15 K, there are one invariant point, two univariate curves, and two solid-phase crystallization zones (NH₄Cl and CaCl₂·6H₂O). In addition, the unreported Pitzer parameters were obtained based on the solubility data of the ternary systems. Using the Pitzer model, the solubilities of salts in the ternary systems NH₄Cl–LiCl–H₂O and NH₄Cl–CaCl₂–H₂O at 258.15 K were modeled in detail. The modeling solubilities are in great agreement with the experimental results, indicating that the Pitzer model can be well applied to study the thermodynamic phase equilibria at subzero temperature.

The dielectric constant measures the influence of an electric field on a material. As it probes solute–solvent interactions within a fluid, it could shed light on reactions such as the hydrothermal conversion of biomass to biofuels. However, such measurements are difficult to obtain due to the low temperature and electrical conductivity operating limits of conventional dielectric constant apparati. An apparatus was designed to measure the dielectric constant of fluids up to 220 °C consisting of a cylindrical resonant cavity that operates in TM₀₁₀ mode at 1 GHz. The liquid sample is contained in a bespoke quartz tube reactor with an internal thermocouple and a pressure transducer. The sample temperature is manipulated with a dual zone heating unit. The system was validated with pure subcritical water between 20 to 220 °C and was employed to in situ detect changes in the dielectric constant of five organic solvents up to 200 °C, beyond values currently available in the literature. The maximum deviation from reference data is approximately 5% for water. The maximum deviation extends to 20% with less polar organic solvents when compared to values using single-Debye models in high-temperature regions.

In this work, volumetric, acoustic, viscometric, photon correlation, and near-infrared spectroscopic studies of a biguanide-type antidiabetic drug, metformin hydrochloride (M·HCl), have been reported for binary solutions with water and ternary solutions with d-(+)-glucose in aqueous media. The volumetric and acoustic studies show a kosmotropic nature of M·HCl in aqueous systems (from 0.1534 × 10^–3 mol·kg^–1 to 60.9483 × 10^–3 mol·kg^–1). Structure breaking progresses with increasing temperature (from 290.0 to 330.0 K). Strong interactions between M·HCl and water are revealed by viscometric analysis, and compared to the transition state, the ground state shows more prominent interactions. Again, the studies unveil that water structure breaking occurs with the addition of d-(+)-glucose molecules for ternary systems (up to 10.0 × 10^–3 mol·kg^–1). Self-association of glucose occurs with an increasing concentration of d-(+)-glucose. Water molecules surround glucose molecules more, and the kosmotropic nature of M·HCl is observed (from 10.0 × 10^–3 mol·kg^–1 to 20.0 × 10^–3 mol·kg^–1). Photon correlation and near-infrared spectroscopy studies also yielded the same result. Structure making progresses with rising temperature (from 290.0 to 315.0 K), but a rise to a greater extent (from 315.0 to 330.0 K) leads to the breaking of the water structure.

The work presents precision data on the heat capacity of adenine (C₅H₅N₅; IUPAC name: 9H-purin-6-amine; CAS Number: 73–24–5) and guanine (C₅H₅N₅O; IUPAC name: 2-amino-1,9-dihydro-6H-purin-6-one; CAS Number: 73–40–5) in the range 6–330 K obtained by adiabatic calorimetry. The data were used to calculate the thermodynamic functions (entropy, enthalpy increment, and Gibbs reduced energy) between 0 and 330 K. For the first time, a λ-type anomaly was revealed in the functional behavior of the heat capacity of guanine in the range of 225–250 K, which indicates the presence of a second-order phase transition in this temperature range. The anomalous component was segregated from the experimental data. Approximation of the anomalous component was done to find its thermodynamic parameters (entropy and enthalpy increment) and the critical temperature of phase transition: T_tr = 242.7 ± 0.1 K, ΔS_an = 0.042 ± 0.004 J·mol^–1K^–1, ΔH_an = 10.2 ± 1.0 J·mol^–1.

The present discussion embodies the studies on binary mixtures containing triethylamine with 2-methyl-1-propanol, 2-propanol, and 1-butanol. For this purpose, the density and speed of sound for pure liquids and their binary mixtures were measured within the temperature range 293.15–313.15 K, while viscosity was measured from 298.15 to 308.15 K. Various excess and deviation parameters have been calculated using the measured properties. The calculated parameters reveal the formation of strong intermolecular interactions upon mixture formation. Excess and deviation parameters were fitted to the Redlich–Kister polynomial. The correlation ability of viscosity-related models has also been tested for the studied binary mixtures.

Aqueous biphasic systems (ABS) have recently emerged as an economic and sustainable solution for the separation and isolation of biomolecules. Ethyl lactate (EL) is an attractive phase-forming component, as it is a biorenewable, biodegradable, and nontoxic solvent. In this study, cloud points and tie-line data for ethyl lactate (EL)-based aqueous biphasic systems (ABS) with four choline salts─choline bicarbonate (ChHCO₃), choline chloride (ChCl), choline bitartrate (ChBitar), and choline dihydrogen citrate (ChH₂Cit)─were experimentally determined at 298.2 and 328.2 K. For both temperatures, three models were used to fit the data: the three-parameter Merchuk’s equation, a two-parameter correlation, and the effective excluded volume. The molecular-level interactions and dynamic behavior within the ABS systems were investigated using diffusion nuclear magnetic resonance. EL–ChH₂Cit showed the most significant changes in diffusion coefficients and water shifts, indicating increased viscosity and altered water structuring. In contrast, ChCl effects were primarily viscosity-driven, ChBitar exhibited complex, nonlinear trends suggestive of solvation or aggregation phenomena, whereas ChHCO₃ uniquely displayed peak splitting, pointing to multiple EL environments. This work provides novel insights into the design of green solvent systems and contributes to the development of alternatives to hazardous organic solvents, with potential applications across biotechnology, pharmaceuticals, and the green chemistry industries.

In the industrial synthesis of isobutyl acetate (IbAC) from isobutyl alcohol (IbOH) and acetic acid, excess IbOH forms an azeotrope with IbAC. Extractive distillation is widely used for azeotrope separation, yet conventional solvents are often toxic and volatile. Biobased solvents, being biodegradable and ecofriendly, offer a promising alternative. Screening with the conductor-like screening model for segment activity coefficient identified cinene and α-pinene as effective entrainers to break the IbOH–IbAC azeotrope. Ternary vapor–liquid equilibrium experiments confirmed that both solvents, when added at 20 mol %, eliminated the azeotrope. The nonrandom two-liquid model accurately correlated the experimental data. However, α-pinene formed a new azeotrope with IbOH at an atmospheric pressure. Toxicity assessment showed cinene has lower mammalian toxicity but higher aquatic toxicity than those of conventional solvents. Quantum chemical calculations revealed that stronger van der Waals interactions between cinene and IbAC reduce the activity coefficient of IbAC, facilitating separation.

Mixtures that possess a lower critical solution temperature (LCST) phase behavior form a homogeneous single phase at temperatures below the LCST and separate into two liquid phases (water-rich, WR, and water-scarce, WS) above the LCST. This unique thermoresponsive phase behavior can be leveraged in various thermodynamic cycles, which are used for applications such as desalination and dehumidification. In addition to their phase diagram, the performance of aqueous LCST mixtures is dictated by their water activity (i.e., the chemical potential of water in the mixture). Recently, a ternary mixture of oleic acid (OA), lidocaine (LD), and water was shown to possess an LCST of ∼298.15 K, but the phase diagram over the full range of concentrations and water activity has not been reported. In this work, we experimentally characterize the phase diagram (liquid–liquid equilibrium, LLE), water activity (vapor–liquid equilibrium, VLE), chemical potential of water, and osmotic pressure of OA/LD/H₂O under conditions that are relevant to the aforementioned applications. Our results suggest that OA/LD/H₂O can outperform other LCST mixtures (e.g., ionic liquids) given its broad phase diagram, low LCST, and purity of the two phases after separation.