Excess Enthalpies Of Binary Mixtures Research Articles

Excess Enthalpies for Binary Mixtures of the Reactive System Acetic Acid + n-Butanol + n-Butyl Acetate + Water: Brief Data Review and Results at 313.15 K and Atmospheric Pressure

The data on molar excess enthalpies, HmE, for the binary mixtures acetic acid + n-butanol, acetic acid + n-butyl acetate and n-butanol + n-butyl acetate at 313.15 K and atmospheric pressure were obtained with use of the C80 isothermal mixing calorimeter (Setaram). The correlation of the data was carried out using the NRTL model and Redlich-Kister equation. A comparative analysis with the literature data on all available binary subsystems of the quaternary system was carried out. Other thermodynamic properties (Cp,mE, SmE, ΔmixSm, GmE and ΔmixGm) of the binary systems were estimated using literature data and well-known formulas of classical thermodynamics.

μFlowCal – High‐Resolution Differential Flow Microcalorimeter for the Measurement of Heats of Mixing

AbstractThis work presents the description, calibration, test and performance evaluation of a new flow microcalorimeter. The μFlowCal is a differential heat conduction, flow microcalorimeter, designed to work in isothermal conditions, in differential mode and in the absence of gas phase, requiring small amounts of sample (200 μL). Both the microcalorimeter and its operational methodology were optimized to measure the heat of mixing of fluids with moderate viscosity and volatility. The microcalorimeter has a sensitivity of 116 μV mW−1 and a level of detection of 170 nW. A very good performance (uncertainty <5 %) was obtained for the selected test processes: enthalpy of dilution of aqueous sucrose solutions and excess enthalpy of binary mixtures of decane‐octanol. The μFlowCal prototype is a new tool in micro‐scale physical chemistry and a step forward concerning signal resolution and sample volume. Nowadays, these are major requirement for the study of novel promising solvents and their mixtures.

Excess Enthalpies of Binary Mixtures in Liquid State, near the Critical Points and Gas State

Excess Enthalpies of Binary Mixtures in Liquid State, near the Critical Points and Gas State

Excess volume and excess enthalpy of binary mixtures composed of 1,2-dichloropropane and 1-alkanol (C5-C8)

The excess molar volumes and excess molar enthalpies at T=298.15 K and atmospheric pressure for the binary systems {CH3CHClCH2Cl (1)+CH3(CH2)n−1OH (2)} (n=5 to 8) have been determined over the whole range of composition from the density and heat flux measurements using a digital vibrating-tube densimeter and an isothermal calorimeter, respectively. The measured excess molar volumes of all binary mixtures showed positive symmetrical trend with values increasing with chain length of 1-alkanol. Similarly, excess enthalpy values of all binary mixtures showed skewed endothermic behavior with values increasing with chain length of 1-alkanol. The maxima of excess molar enthalpy values were observed around x1=0.65 with excess enthalpy value ranging from 1,356.8 J/mol (1-pentanol) to 1,543.4 J/mol (1-octanol). The experimental results of both HmE and VmE are fitted to a modified version of Redlich-Kister equation using the Pade approximant to correlate the composition dependence. The experimental HmE data were also fitted to three local-composition models (Wilson, NRTL, and UNIQUAC). The correlation of excess enthalpy data in these binary systems using UNIQUAC model provides the most appropriate results.

Reparameterization of COSMO-SAC for Phase Equilibrium Properties Based on Critically Evaluated Data

COSMO-SAC model was reparameterized with use of the critically evaluated data generated by the NIST ThermoData Engine for vapor–liquid equilibria, excess enthalpies for binary mixtures, and activity coefficients of binary mixture components. The calculated σ-profile library contained 897 individual compounds. The temperature-dependent σ profiles included contributions of up to 40 conformers of a molecule. Splitting of the H-bonding σ profiles into OH and non-OH parts decreased the root-mean square deviation from the experimental data points by about 10% compared to the model using one H-bonding parameter. The original UNIFAC model demonstrated comparable performance with the more advanced COSMO-SAC variation. The challenges of uncertainty evaluation for parameters of the model and the predicted values are discussed.

Excess enthalpy of monoethanolamine + ionic liquid mixtures: how good are COSMO-RS predictions?

Mixtures of ionic liquids (ILs) and molecular amines have been suggested for CO2 capture applications. The basic idea is to replace water, which volatilizes in the amine regeneration step and increases the parasitic energy load, with a nonvolatile ionic liquid solvent. To fully understand the thermodynamics of these systems, here experimental excess enthalpies for binary mixtures of monoethanolamine (MEA) and two ILs: 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][NTf2], and 1-(2-hydroxyethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [OHemim][NTf2], were obtained by calorimetry, using a Setaram C80 calorimeter, over the whole range of compositions at 313.15 K. Since it is the temperature derivative of the Gibbs energy, enthalpy is a sensitive measure of intermolecular interactions. MEA + [hmim][NTf2] is endothermic and MEA + [OHemim][NTf2] is exothermic. The reliability of COSMO-RS to predict the excess enthalpy of the (MEA+IL) systems was tested based on the implementation of two different molecular models to define the structure of the IL: the IL as separate cation and anion [C+A] and the IL as a bonded single specie [CA]. Quantum-chemical calculations were performed to gain additional insight into the intermolecular interactions between the components of the mixture. For MEA + [hmim][NTf2] both the [C+A] and [CA] models predict endothermic behavior, but the [CA] model is in better agreement with the experimental results. For MEA + [OHemim][NTf2] the [C+A] model provides the best match to the experimental exothermic results. However, what is really surprising is that two different conformations of the cation-anion pair with nearly identical energies in the [CA] model result in completely different (exothermic vs endothermic) predictions of the excess enthalpy. Nonetheless, the results do show that the influence of the structure of the IL on the thermodynamic behavior of the mixture (endothermic vs exothermic) can be attributed to hydrogen bonding between the cation and the MEA molecule. However, this study highlights the importance of carefully selecting the molecular model and conformation in order to obtain even qualitatively correct predictions with COSMO-RS. The fact that even very slightly different conformations of the IL can drastically change the thermodynamic estimations using COSMO-RS is of significant concern. Overall, we believe the present work provides a better understanding of the behavior of mixtures involving amines and ILs, which is an important aspect to consider when evaluating the use of such solvent mixtures in CO2 capture technologies.

Vapor–Liquid Equilibrium, Excess Molar Enthalpies, and Excess Molar Volumes of Binary Mixtures Containing Methyl Isobutyl Ketone (MIBK) and 2-Butanol, tert-Pentanol, or 2-Ethyl-1-hexanol

Phase equilibrium and calorimetric measurements provide complementary data that are vital for process models. The combined use of vapor–liquid equilibrium (VLE) data and excess enthalpies (HE) makes the thermodynamic model more reliable in extrapolation outside the conditions of the measurement. This is important during the tight time schedule of process development. In this work, phase equilibrium and excess enthalpies of binary mixtures were measured by using three apparatuses. Two types of VLE runs were conducted by using a circulation still of the Yerazunis-type and by using Agilent headspace sampler with a gas chromatograph (HS-GC). A SETARAM C80 calorimeter equipped with a flow mixing cells was taken into use for excess enthalpy measurements. New data of phase equilibrium, excess molar enthalpy, and excess molar volume were obtained for industrially relevant binary mixtures of methyl isobutyl ketone (MIBK) with alcohols (2-butanol, tert-pentanol, 2-ethyl-1-hexanol). Excess enthalpy data at 298.15 K are well in line with equilibrium data obtained in the range of (294 to 368) K. Azeotropic behavior was observed in the MIBK + tert-pentanol system. The experimental data were used for the optimization of Wilson and Redlich–Kister equation parameters.

Sifting Ionic Liquids as Additives for Separation of Acetonitrile and Water Azeotropic Mixture Using the COSMO-RS Method

The phase behavior of the ternary acetonitrile + water + ionic liquid system was predicted using the COSMO-RS method. The effects of different ionic liquids on the separation of acetonitrile + water were discussed. It was found that the influence of anions [OAc]− and [Cl]− on the acetonitrile + water mixture is strong, while the cations have fewer effects on the mixture. The interaction energies and mixing enthalpies of binary acetonitrile + ionic liquid and water + ionic liquid systems were predicted indicating that the interaction energy between molecules is stronger in the water + ionic liquid mixture than in the acetonitrile + ionic liquid system. The excess enthalpies of binary mixtures mainly depend on the hydrogen bonds formed between water (or acetonitrile) and ionic liquids. Ionic liquids [EMIM][OAc] and [EMIM]Cl are expected to be favorable solvents and supposed to have practical applications in the separation of acetonitrile from aqueous solution.

Thermodynamic properties of chiral fenchones in some solutions at T = 298.15 K

Excess enthalpies for binary mixtures ( S-fenchone + ethanol/benzene/cyclohexane/carbon tetrachloride) were measured over the whole concentration at T = 298.15 K. The experimental results were compared with the values obtained from the UNIFAC, COSMO-RS and regular solution theory. Excess enthalpies of binary mixtures of R-fenchone and S-fenchone in ethanol, benzene, and cyclohexane solution at different specified mole fractions of fenchone have been measured under the same conditions. With the decreasing of the specified mole fraction of fenchone in different solutions, the excess enthalpies of mixing of chiral orientated solutions increased and became close to zero. Results were compared with those of chiral limonene in ethanol solution. Pair interaction energies were also investigated.

Thermodynamics of biofuels: Excess enthalpies for binary mixtures involving ethyl 1,1-dimethylethyl ether and hydrocarbons at different temperatures using a new flow calorimeter

Excess molar enthalpies for the binary systems: (ethyl 1,1-dimethylethyl ether + heptane); (ethyl 1,1-dimethylethyl ether + cyclohexane); (ethyl 1,1-dimethylethyl ether + toluene); (cyclohexane + toluene), and (toluene + heptane) have been measured at T = (298.15 and 313.15) K using a new isothermal flow calorimeter developed in the laboratory. The technique was previously checked by measuring test systems. The experimental results have been correlated with the Redlich–Kister polynomial equation. The mixing effects observed and the influence of the temperature are discussed.

Excess enthalpies of binary mixtures of some propylamines + some propanols at 298.15 K

The molar excess enthalpies of 1,2- and 1,3-propanediamine + 1- or 2-propanol and 1,2- and 1,3-propanediol + 1- or 2-propaneamine have been determined at 298.15 K using a twin-microcalorimeter for a series of runs over the whole range of mole fractions. All excess enthalpies were large exothermic, in particular, the systems of amines + propanediols were more than −5 kJ mol −1 at the minimum. Primary or secondary alcohols and amines showed systematically different enthalpic behaviors. Equilibrium constant K1 expressed in terms of mole fractions and standard enthalpy of the formation of a 1:1 complex have been evaluated by ideal mixtures of momomeric molecules and their associated complexes.

Molar excess enthalpies of binary mixtures of [tributyl phosphate + {CH 3(CH 2) nOH ( n = 0 to 3)}] at 298.15 K

The excess molar enthalpies ( H m E ) of binary mixtures between tributyl phosphate (TBP) and aliphatic alcohols {CH 3(CH 2) n OH, ( n = 0 to 3)} were measured with a TAM air isothermal calorimeter at 298.15 K and atmospheric pressure. The results of H m E for { xTBP + (1 − x)CH 3OH} are negative but positive for { xTBP + (1 − x)C 3H 7OH} and { xTBP + (1 − x)C 4H 9OH} in the whole range of composition, while the values of H m E for { xTBP + (1 − x)C 2H 5OH} change from positive values at low x to small negative values at high x and the curve become S shaped. The experimental results have been correlated with the Redlich–Kister polynomial equation. The excess partial molar enthalpies at infinite dilution were determined for each mixture. IR spectra of the mixtures were measured to investigate the effect of hydrogen bonding in the mixture.

Excess enthalpies of binary mixtures of 2-ethoxyethanol with four hydrocarbons at 298.15, 308.15, and 318.15 K : An experimental and theoretical study

New experimental data are reported for the thermodynamic investigation of the intermolecular and intra-molecular hydrogen bonding in 2-ethoxyethanol + hydrocarbons. The excess enthalpies of the mixtures of 2-ethoxyethanol + n-hexane, or cyclohexane, or benzene, or n-octane at three temperatures (298.15, 308.15, and 318.15 K) were measured. The data are correlated with the statistical thermodynamic model non-random hydrogen bonding (NRHB) which accounts for both types of hydrogen bonds and was recently developed by the authors. A single set of hydrogen bonding parameters is used for all the alkoxyethanol systems and for the recently calculated thermodynamic properties. The results showed a satisfactory agreement between experimental and calculated data and the contributions of all different types of molecular interactions were calculated. The intra-molecular hydrogen bonding contribution to the heats of mixing is exothermic and significant. The calorimetric measurements are combined with dielectric ones and the derived Kirkwood factor is used to interpret the physicochemical behaviour of our systems.

Excess enthalpies of binary mixtures containing poly(propylene glycols) + benzyl alcohol, or + m-cresol, or + anisole at 308.15 K and at atmospheric pressure

Excess enthalpies, H E, of binary mixtures containing poly(propylene glycols) of different molecular masses + benzyl alcohol, or + m-cresol, or + anisole were determined using a flow microcalorimeter at 308.15 K and at atmospheric pressure. Data was correlated using the Redlich–Kister polynomial. Results were qualitatively discussed in terms of molecular interactions and of the regular solution model.

Excess enthalpies of binary mixtures with endothermic–exothermic changes in mixing processes: empirical correlations

Four empirical correlations are used to fit experimental data for excess enthalpies in binary mixtures with endothermic to exothermic changes in mixing processes. The validity, accuracy, and number of empirical coefficients required for an adequate fit are studied with the aim of finding criteria for selecting the best correlation for this case, or at least to make some recommendations for the use of the models. To this end, we used data for 60 thermodynamic states, which were fitted by using from 4 to 14 adjustable coefficients.

Excess Enthalpies of {CH3(CH2)nCN,n= 5 to 12} + Methyl Methylthiomethyl Sulfoxide or + Dimethyl Sulfoxide at 298.15 K

Excess enthalpies of binary mixtures between each of {CH 3 (CH 2 ) n CN (n = 5-12)} and methyl methylthiomethyl sulfoxide or dimethyl sulfoxide have been determined at 298.15 K. All mixtures show positive enthalpy changes over the whole range of mole fractions. Excess enthalpies of the mixtures of nitriles increased with increasing size of the aliphatic groups. The increments of dipole interaction terms of μ 1 2μ 2 2(r 1 + r 2 ) -6 on excess partial molar enthalpies at infinite dilution showed different behavior on the border of pentanenitrile.

Excess Enthalpies of Binary Mixtures of 1-Hexene with Some Ethers at 25°C

Measurements of excess molar enthalpies at 25°C in a flow microcalorimeter, are reported for the four binary mixtures formed by mixing 1-hexene with either 2- methyltetrahydrofuran, or methyl tert-butyl ether, or diisopropyl ether, or di-n-butyl ether. Smooth Redlich–Kister representations of the results are presented. It was found that the Liebermann–Fried model also provided good representations of the results.

Excess Enthalpies of Binary Mixtures of 1-Hexene with Some n-Alkanes at 298.15 K

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for mixtures of 1-hexene with n-heptane, n-octane, n-decane, n-dodecane, and n-tetradecane. Smooth Redlich−Kister representations of the results are described. It was found that the Liebermann−Fried model also provided good representations of the data.

Excess enthalpies of binary mixtures of 1-hexene with some branched alkanes at the temperature 298.15 K

Abstract Measurements of excess molar enthalpies at the temperature 298.15 K in a flow microcalorimeter are reported for the five binary mixtures formed by mixing 1-hexene with the branched alkanes: 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane, 2,3-dimethylbutane, and 2,2,4-trimethylpentane. Smooth Redlich–Kister representations of the results are described. It was found that the Liebermann–Fried model also provided good representations of the results.

Excess enthalpies of alkane-1-amines {C nH 2 n+1 NH 2, n = 3–8} + methyl methylthiomethyl sulfoxide and +dimethyl sulfoxide at 298.15 K

Excess enthalpies of binary mixtures between each of alkane-1-amines {C n H 2 n+1 NH 2, n=3–8} and methyl methylthiomethyl sulfoxide (MMTSO) or dimethyl sulfoxide (DMSO) have been determined at 298.15 K. All mixtures showed positive enthalpy changes over the whole range of mole fractions. The limiting excess partial molar enthalpies of the aliphatic amines, H 1 E,∞, of all the mixtures with MMTSO or DMSO studied were smaller than those of MMTSO or DMSO, H 2 E,∞, respectively. Linear relations are obtained between limiting excess partial molar enthalpies and number of methylene groups.