Abstract Thermodynamic models used to design deep eutectic solvents (DES) rely on activity coefficients calculated from experimental solid–liquid equilibrium (SLE) data, and their reliability depends on the consistency of the underlying data. The SLE data are particularly uncertain for systems containing choline chloride (ChCl), a thermally unstable, hygroscopic salt that decomposes before melting. This work assesses the consistency of SLE data for ChCl-based DES reported in the literature using component activity coefficients. The activity coefficients of ChCl are calculated directly from the SLE data using the lower and upper bounds of the ChCl melting properties. Because these bounds cover the physically acceptable ChCl melting properties range, the assessment does not depend on the selection of ChCl melting properties. The activity coefficients of ChCl shifted abruptly across its solid–solid transition temperature in all systems examined, indicating that the data above and below the solid–solid transition are internally inconsistent. The data for ChCl-rich mixtures measured above the solid–solid transition were difficult to reconcile with the expected nonideality of the mixtures, consistent with the limited thermal stability of ChCl. These findings are intended to guide the selection of consistent SLE data for developing thermodynamic or machine learning models.
Abstract The vapor–liquid-phase equilibrium (VLE) data for binary systems 1,3,5-trimethylbenzene (1,3,5-TMB) + 2-ethyltoluene (2-ETL), 1,3,5-TMB + N-methyl-2-pyrrolidone (NMP), 2-ETL + NMP, 1,3,5-TMB + dimethyl phthalate (DMP), 2-ETL + DMP and for ternary systems 1,3,5-TMB + 2-ETL + NMP, 1,3,5-TMB + 2-ETL + DMP were measured at 101.3 kPa. The data were tested for thermodynamic consistency by Fredenslund’s test and the Van Ness test. The VLE data were correlated using the Wilson, NRTL, and UNIQUAC thermodynamic models, and the binary interaction parameters for each model were obtained. The root-mean-square deviation and average absolute deviation were calculated to evaluate the accuracy of these models, and the results show that the experimental values are in good agreement with the calculated ones. The VLE data for the two ternary systems were predicted using the binary interaction parameters, and the predicted ternary VLE data are consistent with the experimental data. This study provides reliable fundamental data for the design and development of the 1,3,5-TMB/2-ETL separation process.
Abstract Under ambient or near-ambient conditions, ionic liquids have shown potential in oral and biomedical applications, where their viscosity plays a key role in processability, diffusion, penetration, and transport behavior. Beyond these ambient-condition applications, gas-loaded ionic liquids are also relevant to gas absorption, separation, and other CO2-related processes, in which dissolved gases can significantly alter the viscosity and transport behavior of ionic liquids. Therefore, systematic viscosity data for CO2-containing ionic-liquid mixtures over broad temperature, pressure, and composition ranges are needed to understand their transport behavior and develop predictive models. Accordingly, in this work, the viscosities of CO2-saturated [Hmim][OTf] and [Hmim][Tf2N] were measured from 303.15 to 343.15 K and at pressures up to 7.5 MPa using a high-pressure capillary viscometry system. The standard uncertainties were u(T) = 0.023 K and u(p) = 0.0025 MPa, while the expanded relative uncertainty of viscosity was Ur(η) < 0.05 at an approximately 0.95 coverage probability (k = 2). The experimental results show that the viscosity decreases markedly with increasing CO2 loading, and under low-temperature conditions, the viscosity reduction exceeds 50% when the CO2 mole fraction is around 0.3. The Soft-SAFT equation of state combined with entropy scaling was then employed to correlate the viscosity behavior of the two systems. The results show that the model satisfactorily correlates the effects of CO2 loading and temperature on mixture viscosity.
Abstract Acoustic parameters were determined for two ternary liquid systems consisting of equal concentrations of donor–acceptor {[DPE] = [Amine]} from 0.03 mol·kg–1 to 0.31 mol·kg–1 of diphenyl ether (DPE), and one of the two structurally different primary amines [n-hexylamine (NHA), cyclohexylamine (CHA)] in n-hexane at 303.15 K and at atmospheric (0.1 MPa) pressure. Equal concentrations of solutes are a necessary condition for computing the stability constants (K) by ultrasonic method. The influence of various noncovalent interactions, concentration, and the structure of the amines on the physicochemical properties of the two liquid mixtures was analyzed. The acoustic data highlighted the dominance of hydrogen-bonded interactions over the structure-breaking behavior of the components. The optimized geometries of the solutes and complexes in n-hexane, obtained by density functional theory (DFT) analysis, revealed the existence of C–H···O, C–H···N, C–H···π, and N–H···O interactions in the two systems. This was also established by the NCI and RDG plots for the two systems. The experimental K values correlated satisfactorily with the theoretically computed interaction energies. These results provide insights into the influence of the H-donor structure on the formation constants and stability of amine-diphenyl ether (DPE) complexes. The results show that NHA forms stronger complexes than CHA with DPE.
Abstract The viscosity (η) and ultrasonic speed (c) of binary mixtures containing tert-butanol (1) and hydrocarbons (n-hexane, cyclohexane, benzene, ethylbenzene, and cumene) (2) were recorded at temperatures from 298.15 to 318.15 K and at 0.1 MPa pressure. Based on the collected data, deviation in viscosity (Δη), deviation in ultrasonic speed (Δc), excess isentropic compressibility (κSE), and excess Gibbs free energy of activation (ΔG*E) were determined and correlated using the Redlich–Kister equation. TheΔη, ΔG*E, and Δc follow the order: n-hexane > benzene > ethylbenzene > cumene > cyclohexane, while the corresponding values shows an inverse trend. Furthermore, the changes in Δη and κSE were examined using a semiempirical association-based modeling approach. The theoretical estimates aligned well with the experimental findings, and the temperature effect on these properties was systematically calculated. Throughout the whole temperature range, all systems exhibited negative values ofΔη, ΔG*E, and Δc values, indicating that weaker interactions between unlike molecules predominate compared with those in the pure components.
