Excess Molar Enthalpies Research Articles

Comparison of methods for calculating the enthalpy of vaporization of binary azeotropic mixtures

Objectives. To calculate the molar enthalpy of vaporization of binary homogeneous mixtures based on isothermal and isobaric vapor–liquid equilibrium data, and to compare the results of calculation of molar enthalpy of vaporization by different methods with experimental data.Methods. Simulation of the vapor–liquid equilibrium of binary systems according to the Non-Random Two Liquid “local compositions” equation and thermodynamic calculations of molar vaporization enthalpies of binary mixtures at different conditions of vapor–liquid equilibrium were used.Results. Arrays of calculated data were obtained with regard to molar enthalpies of vaporization for 25 compositions of binary azeotropes (isothermal, isobaric conditions of phase equilibrium), and the full range of compositions of the benzene–ethanol system at atmospheric pressure.Conclusions. The accuracy of thermodynamic methods for calculating the vaporization enthalpy of binary azeotropic mixtures according to vapor–liquid equilibrium data is higher in 85% of cases for isothermal, and in 75% of cases for isobaric conditions. By taking into account the influence of temperature on the activity coefficients of components in the liquid phase, the values of excess molar enthalpy both for azeotrope compositions and for the full concentration range of the benzene–ethanol system under isobaric conditions of liquid–vapor phase equilibrium can be accurately reproduced.

Comments Regarding “Measurement and Modeling of Excess Molar Volume and Excess Enthalpy of n-Tridecane or n-Tetradecane with Decalin by Application of PFP Theory”

Comments Regarding “Measurement and Modeling of Excess Molar Volume and Excess Enthalpy of n-Tridecane or n-Tetradecane with Decalin by Application of PFP Theory”

Experimental and computational study of binary mixture ethanolamine and 2-amino-2-methyl-1-propanol

The present work involves experimental and computational investigations into the density of pure and mixed states of ethanolamine (ET) and 2-amino-2-methyl-1-propanol (AMP) under a pressure of 1 atm and temperatures ranging from 293.15 K to 333.15 K The density data were used to derive the excess molar volume, thermal expansion coefficient, and isothermal coefficient of pressure excess molar enthalpy. The Redlich–Kister equation was employed to calculate the excess molar and its accompanying coefficients. In the gas phase, density functional theory (DFT) was utilized to explore the most stable structures of ET … ET, AMP … AMP, and the ET … AMP mixture. Molecular dynamics simulation (MD) was used to calculate the structural properties of these mixtures in the liquid phase. Radial distribution function (RDFs) combined distribution function (CDF) and spatial distribution function (SDF) in different mole fractions calculated in the liquid phase. The intramolecular and intermolecular interactions of ethanolamine and AMP were obtained using the radial distribution function in different molar fractions. It was found that the ethanolamine molecule has a greater tendency to form intramolecular hydrogen bonds, while the AMP molecule has a greater tendency to form intermolecular hydrogen bonds.

Measurement and prediction of excess molar enthalpies of ternary mixtures involving ether with 1-alkanol and n-alkane

This work aims to experimentally determine the excess molar enthalpies at 298.15 K and atmospheric pressure for the ternary mixture {x1 methyl tert-butyl ether (MTBE) + x2 1-pentanol + (1 − x1 − x2) heptane} and the corresponding binary system {x 1-pentanol + (1 − x) heptane}, across the whole composition range. The excess molar enthalpy of the ternary system is positive throughout the composition range. Except for a region around compositions rich in 1-pentanol, the ternary contribution to the excess molar enthalpy is also positive and its representation is asymmetric.A systematic review of the currently accessible literature on excess molar enthalpy for the ternary mixtures containing ethers with 1-alkanol and 1-alkane was conducted. According to our searches, no previous experimental measurements of excess enthalpy for the ternary combination under study have been reported.The ternary excess enthalpy values and the involved binary mixtures were estimated using the UNIFAC group contribution model. Furthermore, several empirical equations for estimating ternary properties from binary results were tested against the experimental data to evaluate their predictive accuracy for ternary properties.

Modeling of experimental excess molar enthalpy with Wilson, UNIQUAC, and NRTL for mixtures of acetophenone with chloro derivatives of ethane and ethene at T = 298.15 K

The excess molar enthalpy HmE, was determined for systems consisting of acetophenone with chloro alkanes and alkenes derivatives. These derivatives include 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, trichloroethene and tetrachloroethene at a temperature of T = 298.15 K. The Redlich-Kister relation fitting was used to analyze the HmE values obtained from this experimental data. Additionally, the excess partial molar enthalpy HiE was derived from the experimental HmE values. The intermolecular interaction function such as ∂HiE∂xi and ∂HjE∂xjwere also calculated. For the system consisting of acetophenone + 1,1,1-trichloroethane or + tetrachloroethene, the HmE values were found to be positive. Conversely, the HmE values for acetophenone + 1,2-dichloroethane or + 1,1,2,2- tetrachloroethane or + trichloroethene were observed to be negative. The magnitude of the HmE values increased in chloroethanes as the number of chlorine atoms increased, and became more negative in chloroethenes. Based on the local composition theory, the Wilson model, the universal quasichemical (UNIQUAC) model, and the non-random two-liquid (NRTL) model were used to correlate these thermodynamic data. The results showed good agreement with the experimental enthalpy data.

Measurement and Modeling of Excess Molar Volume and Excess Enthalpy of n-Tridecane or n-Tetradecane with Decalin by Application of PFP Theory

Measurement and Modeling of Excess Molar Volume and Excess Enthalpy of n-Tridecane or n-Tetradecane with Decalin by Application of PFP Theory

Excess Enthalpies Analysis of Biofuel Components: Sunflower Oil-Alcohols Systems.

This study addresses the pressing issues of energy production and consumption, in line with global sustainable development goals. Focusing on the potential of alcohols as "green" alternatives to traditional fossil fuels, especially in biofuel applications, we investigate the thermochemical properties of three alcohols (n-propanol, n-butanol, n-pentanol) blended with sunflower oil. The calorimetric analysis allows for the experimental determination of excess enthalpies in pseudo-binary mixtures at 303.15 K, revealing similarities in the trends of the curves (dependence on concentrations) but with different values for the excess enthalpies for each mixture. Despite the structural differences of the alcohols studied, the molar excess enthalpy values exhibit uniformity, suggesting consistent mixing behavior. The peak values of excess enthalpies for systems with sunflower oil and n-propanol, n-butanol and n-pentanol are, respectively, 3255.2 J/mole, 3297.4 J/mole and 3150.1 J/mole. Both the NRTL and Redlich-Kister equations show satisfactory agreement with the obtained values.

Thermophysical properties of ethyl levulinate and n-alkanol systems

Some thermophysical properties such as densities, speeds of sound, refractive indices, and heat flows of the binary systems ethyl levulinate and n-alkanols (methanol, ethanol, 1-propanol, and 1-butanol) are reported in the temperature range T = (283.15–313.15) K and at p = 100 kPa. From these experimental data, the excess properties were calculated and correlated with the composition using a modified Redlich–Kister equation. The excess molar volumes were negative for short-chain alcohols and positive for 1-propanol and 1-butanol. The excess refractive indices exhibited the opposite behaviour. The excess isentropic compressibilities were negative and the excess molar enthalpies, were positive. The perturbed chain statistical associating fluid theory equation of state (PC-SAFT EoS) was successfully applied to correlate the densities of the mixtures, and good qualitative results in the computation of the excess molar enthalpy were obtained. Furthermore, Schaaff’s collision factor theory (SCFT) and the Laplace mixing rule were coupled with PC-SAFT to predict the speed of sound and the refractive index, respectively.

Local composition-regular solution theory for analysis of pharmaceutical solubility in mixed-solvents

Local composition regular solution theory (LC-RST) model was developed by introducing non-equal i–j and j–i parameters into regular solution theory (RST) to account for specific molecular interactions. The LC-RST model was applied to the correlation of solubilities of active pharmaceutical ingredients (API) in hydrogen bond donor (HBD) – hydrogen bond acceptor (HBA) mixed-solvent systems. In the assessment of 32 API-mixed-solvent systems that contained 11 different APIs and 1947 data, it was determined that the LC-RST model had a logarithmic average relative deviation (ARDln) in solubility of 0.028, the Wilson model had an ARDln value of 0.24 and the purely predictive RST model had an ARDln value of 1.29. Partial molar excess enthalpies and entropies of the API in the mixed-solvents determined from the LC-RST model allowed estimation of API solubility regions where specific interactions occur between API and HBD-HBA complex molecules. In the correlation scheme, component numbers were designated as API molecule (1) – HBD molecule (2) - HBA molecule (3) and systems were grouped according to HBD molecule interactions with the API (pro-solvent, anti-solvent, synergistic with HBA molecule). Phenomenological parameter sensitivity analysis of the LC-RST model showed that dominant specific interactions tended to be 1–2 or 2–1 molecules for pro-solvent groupings, 2–3 or 2–3 molecules for anti-solvent groupings and all i–j and j-–i molecular pairs for synergistic HBD-HBA molecule groupings. Based on parameters determined from a given API-mixed-solvent system, the LC-RST model allows qualitative prediction of solubilities for other systems. The LC-RST model is simple to apply and it retains inherent predictive characteristics of regular solution theory.

Density and speed of sound of (iodobenzene + n-alkane) liquid mixtures at T = (288.15 to 308.15) K. Application of the Prigogine-Flory-Patterson model

(Iodobenzene + n-alkane) liquid mixtures have been studied experimentally, in terms of densities (ρ) and speeds of sound (c), and theoretically, by the application of the Prigogine-Flory-Patterson (PFP) model. The n-alkanes considered are n-heptane, n-decane, n-dodecane, and n-tetradecane. ρ and c measurements have been performed at a pressure p = 0.1 MPa and in the temperature range T = (288.15 to 308.15) K. Excess molar volumes (VmE) and excess isentropic compressibilities (κSE) have been calculated and correlated by Redlich-Kister polynomials. (∂VmE/∂T)p curves at the same (p,T) conditions have been obtained from correlated VmE values. The mixtures are characterized by the following features: (i) VmE increases with the number of carbon atoms of the n-alkane (n), being negative for n = 7, small and S-shaped with positive and negative values for n = 10, and positive for n = 12 and n = 14; (ii) κSE and (∂VmE/∂T)p are negative, increase with n and are very close to zero for n = 14. From these experimental results and the knowledge of the excess molar enthalpies of mixtures containing fluorobenzene, chlorobenzene or bromobenzene with n-alkanes, we have inferred the presence of structural effects, especially important for n = 7 and less relevant for volumetric properties as n increases. The VmE obtained are compared with those of other (halogenated benzene + n-alkane) liquid mixtures existing in the literature, namely systems with fluorobenzene, chlorobenzene, and bromobenzene. From this comparison and the analysis of the isobaric thermal expansion coefficients of the pure compounds, it is inferred that the interactional effects on VmE do not vary appreciably with the length of the n-alkane, so the observed VmE variation is fundamentally determined by the corresponding variation of the contribution from structural effects. Moreover, the application of the PFP model supports this interpretation, providing free volume contributions to VmE that vary parallelly to VmE with the length of the n-alkane, and interactional contributions that rest approximately constant independently of the n-alkane size.

Application of ERAS-model and PFP theory on excess and deviation properties for binary systems of ionic liquid + amine derivatives

Thermodynamics of mixtures includes ionic liquid 2-hydroxyethylammonium propionate [2-HEAPr] + 1-propanol, 3-amino-1-propanol [AP], 1-amino-2-propanol [MIPA], and monoethanolamine [MEA] were studied. Density ρ, speed of sound u, and refractive index nD of pure and mixtures were measured at T = (298.15, 308.15, 318.15) K. Excess molar volume VmE, excess partial molar volume Vm,iE, excess thermal expansion coefficient αE, isothermal coefficient of excess molar enthalpy (∂Hm∂P)T,x, deviations in isentropic compressibility Δ ks, and refractive index Δ nD were calculated and data correlated with Redlich-Kister polynomial relation. The Prigogine-Flory-Patterson (PFP) and Extended Real Associated Solution (ERAS) models were applied to analyze intramolecular and intermolecular interactions between like and unlike molecules. The accuracy of theoretical models were found to be in agreement with empirical results. Finally, the study confirmed the structures of the ILs using FT-IR and HNMR analysis.

Isobaric Vapor–Liquid Equilibrium Prediction from Excess Molar Enthalpy Using Cubic Equations of State and PC-SAFT

Isobaric Vapor–Liquid Equilibrium Prediction from Excess Molar Enthalpy Using Cubic Equations of State and PC-SAFT

Experimental and theoretical study on physical properties of the systems dimethyl carbonate and diethyl carbonate + pentanol isomers

In many industrial applications that involve solvents, the knowledge of both thermodynamics properties and transport properties play an important role in the design, sustainability, and optimization of processes in different fields of study. However, it is a fact that there is a lack of data and predictive models for the develop of future applications.Taking this into account, in this work we studied the physical properties of carbonates and pentanol isomers as well as their mixtures due to the versality of these solvents in many processes. We present measurements of densities (ρ) and excess molar volumes and enthalpies (VmE, HmE) at 298.15 K for the systems dimethyl or diethyl carbonate + pentanol isomers; and specifically for the systems with diethyl carbonate the surface tensions (σ ) and the surface tension deviations (δσ) at 298.15 K and the viscosities (η), dynamic viscosity deviations (Δη), refractive indexes (nD) and the changes in the refractive index (ΔnD) at 298.15 and 308.15 K. Different theoretical models were applied to obtained data for surface tensions and refractive indexes.

Infinite Dilution Activity Coefficients and Gas–Liquid Partition Coefficients of Organic Compounds in Ionic Liquid 1-Butyl-2,3-dimethylimidazolium Thiocyanate: Measurements and LFER Calculations

Infinite dilution activity coefficients (γi∞) of 31 organic solutes (alkanes, cycloalkanes, olefins, aromatics, chlorinated alkanes, alcohols, and other polar organic solutes) in the ionic liquid (IL) 1-butyl-2,3-dimethylimidazole thiocyanate ([BMMIM][SCN]) were determined by gas–liquid chromatographic (GLC) method in the temperature range of 313.15–353.15 K. The infinite dilution partial molar excess enthalpies (H̅iE, ∞), entropies (TrefS̅iE, ∞), and Gibbs free energies (G̅iE, ∞) of the organic solutes at the reference temperature T = 298.15 K and the solubility parameters (δ3) of [BMMIM][SCN] were derived from γi∞. The gas–liquid partition coefficients (KL) of solutes at different temperatures were calculated by referring to the densities of [BMMIM][SCN]. The linear free energy relationship solvation model was used to fit the KL values, and the KL prediction model was obtained. The selectivity (Sij∞) and capacity (kj∞) of n-hexane (i)/benzene (j) and cyclohexane (i)/benzene (j) at infinite dilution at 323.15 K were calculated. The results were compared with the values of ILs with the thiocyanate anion in the literature.

Thermodynamic Behavior of (2-Propanol + 1,8-Cineole) Mixtures: Isothermal Vapor-Liquid Equilibria, Densities, Enthalpies of Mixing, and Modeling.

Vapor pressures and other thermodynamic properties of liquids, such as density and enthalpy of mixtures, are the key parameters in chemical engineering for designing new process units, and are also essential for understanding the physical chemistry, macroscopic and molecular behavior of fluid systems. In this work, vapor pressures between 278.15 and 323.15 K, densities and enthalpies of mixtures between 288.15 and 318.15 K for the binary mixture (2-propanol + 1,8-cineole) have been measured. From the vapor pressure data, activity coefficients and excess Gibbs energies were calculated via the Barker's method and the Wilson equation. Excess molar volumes and excess molar enthalpies were also obtained from the density and calorimetric measurements. Thermodynamic consistency test between excess molar Gibbs energies and excess molar enthalpies has been carried out using the Gibbs-Helmholtz equation. Robinson-Mathias, and Peng-Robinson-Stryjek-Vera together with volume translation of Peneloux equations of state (EoS) are considered, as well as the statistical associating fluid theory that offers a molecular vision quite suitable for systems having highly non-spherical or associated molecules. Of these three models, the first two fit the experimental vapor pressure results quite adequately; in contrast, only the last one approaches the volumetric behavior of the system. A brief comparison of the thermodynamic excess molar functions for binary mixtures of short-chain alcohol + 1,8-cineole (cyclic ether), or +di-n-propylether (lineal ether) is also included.

Thermodynamics of 2-alkanol + polar organic solvent mixtures. I. Systems with ketones, ethers or organic carbonates

The mixtures 2-propanol or 2-butanol + n-alkanone, or + acetophenone, or + linear monoether, or + cyclic ether, or + linear organic carbonate, or + propylene carbonate have been investigated using thermodynamic data, and in terms of the Flory theory, and the Kirkwood-Buff integrals. The data considered are: excess molar enthalpies (HmE), volumes, entropies, and the temperature dependence ofHmE. The enthalpy of the 2-alkanol-solvent interactions have been determined, and the different contributions to HmE discussed. It is shown that HmE values of the 2-alkanol (fixed) + n-alkanone, or + linear carbonate mixtures change in the same manner that for n-alkanone, or linear carbonate + n-alkane (fixed) systems. In contrast, HmE values of 2-alkanol (fixed) + linear monoether or + n-alkane mixtures change similarly. This set of results suggests that solvent–solvent interactions are determinant in systems with n-alkanone or linear carbonate, while interactions between alcohol molecules are determinant in mixtures with linear monoethers. According to the Flory model, orientational effects in systems with a given 2-alkanol become weaker in the sequence: linear monoether > linear organic carbonate > n-alkanone, and are stronger in solutions with a cyclic monoether than in those with cyclic diethers, and in systems with acetophenone or propylene carbonate than in the mixtures with the corresponding linear solvents. Results obtained from the Kirkwood-Buff integrals are consistent with these findings. The application of Flory model reveals that orientational effects are similar in systems with 1- or 2-alkanols, with the exception of solutions with linear monoethers, where such effects are stronger in mixtures containing 1-alkanols. For the examined systems, the formalism of the Kirkwood-Buff integrals makes no meaningful distinction between solutions with 1-alkanols or 2-alkanols.

Excess Molar Volumes and Enthalpies of Binary Mixtures Containing Furan and Toluene, 1-Octanol or n-Hexane at Temperatures Up to 383.15 K and Pressure Up to 1.6 MPa

Excess Molar Volumes and Enthalpies of Binary Mixtures Containing Furan and Toluene, 1-Octanol or n-Hexane at Temperatures Up to 383.15 K and Pressure Up to 1.6 MPa

Comparison of excess molar enthalpies predicted by UNIFAC model and COSMO-SAC theory with experimental data for some binary mixtures

In this work, the UNIFAC model and COSMO-SAC theory have been applied for prediction of the excess molar enthalpies of some binary mixtures. The predicted values of excess molar enthalpies via both theories show good agreement with the experimental data reported in literature for the mixtures containing polar and non-polar components, with relative errors less than 30%.

Excess molar enthalpies in the binary system of carbon dioxide + ethyl lactate at 298.15 and 303.15 K and 5.0–7.0 MPa

This paper presents an experimental determination of the excess molar enthalpies (HE) for the binary system of carbon dioxide (CO2) + ethyl lactate at temperatures of 298.15 and 303.15 K and pressures in the range of 5.0–7.0 MPa. A maximum exothermic value of approximately 7.4 kJ mol−1 was found, similar to the exotherms observed in our previous work for other binary systems such as CO2 + ester or ether. We discussed this exothermic behavior based on the change-of-state contribution, strong CO2-ester interactions, and unusual intra- and intermolecular hydrogen bonding of ethyl lactate. The experimental HE data correlated well with a composition-dependent equation and the Peng–Robinson equation of state with the van der Waals one-fluid mixing rule.

Measurement of Activity Coefficients at Infinite Dilution for Various Organic Solutes in Deep Eutectic Solvent (1-Butyl-2,3-dimethylimidazolium Chloride + Ethylene Glycol) at Different Temperatures

Activity coefficients at infinite dilution (γ13∞) for organic solutes in deep eutectic solvent (DES) prepared by {1-butyl-2,3-dimethylimidazolium chloride (BDMIM Cl) + ethylene glycol (EG)} at a molar ratio of 1:3 have been measured using the gas–liquid chromatographic method (GLC). The thermal stability of the entrainer was determined by the thermogravimetric analyzer. The measurements were carried out in the temperature range of T = (313.15 to 343.15) K and at atmospheric pressure. The values of the partial molar excess enthalpies at infinite dilution (H1E,∞) were derived from the temperature dependence of the γ13∞∞ values. The entropies (Tref ΔS1E,∞) and Gibbs energies (ΔG1E,∞) of organic solutes at a reference temperature Tref = 323.15 K were also calculated from the γ13∞ values. These excess thermodynamic functions were calculated to further explain the intermolecular interactions occurring between the volatile organic solvents and the prepared deep eutectic solvent. Important separation parameters such as selectivities (Sij∞) and capacities (Kj∞) at infinite dilution were computed from the activity coefficients at infinite dilution data at T = 313.15 K. Selectivity and capacity data were calculated for the industrial mixtures such as cyclohexane/benzene, hexane/thiophene, cyclohexane/ethanol. There results were compared to the literature data comprising deep eutectic solvents and ILs with the cation of 1-butyl-3-methylimidazolium. The investigated solvent was found suitable to separate azeotropes formed by alkanes/alcohols.