Values Of Excess Molar Enthalpies Research Articles

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%.

Measurement and correlation of thermodynamics properties of aqueous solutions containing glycols. Part II: Excess molar enthalpy

In this work, excess molar enthalpies of binary liquid mixtures of {water + ethanol, or + ethylene glycol, or + diethylene glycol, or + triethylene glycol, or + poly(ethylene glycol) 200, or + poly(ethylene glycol)300, or + poly(ethylene glycol)400, or + poly(ethylene glycol)600, or + glycerol} have been determined as a function of composition using a microcalorimeter Thermal Activity Monitor (2277, Thermometric) at 298.15 K and atmospheric pressure. The results were fitted by the Myers-Scott equation, as a function of mole fraction. The values of excess molar enthalpies were exothermic and large. The excess partial molar enthalpies and excess partial molar enthalpies at infinite dilution were calculated. Moreover, the experimental results were used to test the applicability of the Wilson, NRTL and UNIQUAC models. The results of excess molar enthalpies were discussed in terms of molecular interactions.

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.

Experimental and predicted data of excess molar enthalpies and excess molar volumes for the ternary system (1,3-dichlorobenzene + benzene + 1-chlorohexane) at T = 298.15 K

Experimental excess molar enthalpies, densities and excess molar volumes for the ternary system {x1 1,3-dichlorobenzene+x2 benzene+(1−x1−x2) 1-chlorohexane} have been determined at the temperature of 298.15K and atmospheric pressure. Values of excess molar enthalpies were measured using a Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a vibrating-tube densimeter. The results were fitted by means of different variable degree polynomials. Smooth representations of the results are presented and used to construct constant contours of excess molar enthalpy and excess molar volume on Roozeboom diagrams. Several empirical expressions that have been suggested for use with parameters and predicting excess properties of ternary mixtures from the experimental binary data were tested.

Application of the Prigogine–Flory–Patterson model to excess molar enthalpy of binary liquid mixtures of 1-nonanol or 1-decanol with acetonitrile at atmospheric pressure and 298.15, 303.15 and 308.15 K

Excess molar enthalpy data of 1-nonanol+acetonitrile and 1-decanol+acetonitrile mixtures as a function of composition at atmospheric pressure at 298.15, 303.15 and 308.15K have been used to test the applicability of the Prigogine–Flory–Patterson (PFP) model. Both systems exhibit positive excess molar enthalpy values over the whole composition range for the studied temperature range. The model has only one adjustable parameter and correlates the data within a standard deviation up to 309Jmol−1. The interactional contribution of the model is the most important one to describe the experimental values.

Excess Molar Enthalpies of Ternary and Binary Mixtures Containing 2-Methoxy-2-Methylpropane, Ethanol, and Nonane

Forming part of the scientific project entitled “Study on Physical Properties of Mixtures Hydrocarbon + Alcohol + Ether Like Alternative Fuels”, the present article reports experimental data of excess molar enthalpies for the ternary system {x1 2-methoxy-2-methylpropane (MTBE) + x2 ethanol + (1 – x1 – x2) nonane} and the involved binary mixture {x ethanol + (1 – x) nonane} at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently available literature for the ternary mixture under study. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The results were fitted by means of different variable degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The excess molar enthalpies for the binary and ternary system are positive over the whole range of composition. The binary mixture {x ethanol + (1 – x) nonane} is asymmetric, with its maximum displaced toward a high mole fraction of nonane. The ternary contribution is also positive, and the representation is asymmetric.

Excess Molar Enthalpies of Mixtures of (±)-Linalool with Several Alkanols

Excess molar enthalpies are reported for mixtures of (±)-2,6-dimethyl-2,7-octadien-6-ol (linalool) with ethanol, propan-1-ol, propan-2-ol, and butan-1-ol at the temperatures (283.15, 298.15, 313.15, and 328.15) K and atmospheric pressure, covering the whole composition range. The values of excess molar enthalpy at each temperature have been fitted using approximants of Pade. Most of the mixtures show negative values of the excess enthalpy, indicating the formation of attractive interactions, mainly hydrogen bonds, between the molecules of linalool and molecules of the different alkanols.

Excess molar enthalpies of binary systems containing 2-octanone, hexanoic acid, or octanoic acid at T = 298.15 K

An isothermal titration calorimeter was used to measure the excess molar enthalpies ( H E) of six binary systems at T = 298.15 K under atmospheric pressure. The systems investigated include (1-hexanol + 2-octanone), (1-octanol + 2-octanone), (1-hexanol + octanoic acid), (1-hexanol + hexanoic acid), {N,N-dimethylformamide (DMF) + hexanoic acid}, and {dimethyl sulfoxide (DMSO) + hexanoic acid}. The values of excess molar enthalpies are all positive except for the DMSO- and the DMF-containing systems. In the 1-hexanol with hexanoic acid or octanoic acid systems, the maximum values of H E are located around the mole fraction of 0.4 of 1-hexanol, but the H E vary nearly symmetrically with composition for other four systems. In addition to the modified Redlich–Kister and the NRTL models, the Peng–Robinson (PR) and the Patel–Teja (PT) equations of state were used to correlate the excess molar enthalpy data. The modified Redlich–Kister equation correlates the H E data to within about experimental uncertainty. The calculated results from the PR and the PT are comparable. It is indicated that the overall average absolute relative deviations ( AARD) of the excess enthalpy calculations are reduced from 18.8% and 18.8% to 6.6% and 7.0%, respectively, as the second adjustable binary interaction parameter, k bij , is added in the PR and the PT equations. Also, the NRTL model correlates the H E data to an overall AARD of 10.8% by using two adjustable model parameters.

Thermodynamic properties of (ethylbenzene + an alkane or + an alkyl ethanoate): experimental H m E and V m E values

In this work, we present the experimental values of excess molar enthalpies, , and excess molar volumes, , for a set of mixtures composed of ethylbenzene with several alkanes, from heptane to hexadecane, and the first four alkyl ethanoates. In all cases, measurements were made at the two temperatures of 298.15 and of 318.15 K. The mixtures of C6H5C2H5 + C n H2 n +2 present endothermic effects that increase quasilinearly with n, and expansive effects that also increase with n, but quasiexponentially. The influence of temperature on these mixtures produces thermal indices . The aromatic mixtures with alkyl ethanoates, C6H5C2H5 + CH3COOC v H2 v +1, show a different behaviour. In this case, both the diminish quasiexponentially with the increase in v, resulting in < 0 for mixtures with v = 4, and sigmoidal when v = 3. The rise in temperature produces a . In all cases, the experimental values were treated with a suitable polynomial equation that can simultaneously correlate the excess properties with liquid–vapour equilibria data. Finally, a prediction of the values was made with two versions of the UNIFAC group contribution model, although it was necessary to recalculate parameters corresponding to the CH2/ACCH2 and COOC/ACCH2 interactions for the groups of mixtures studied in the version of Dang and Tassios (Ind. Eng. Chem. Des. Dev. 25, 22 (1986)), to obtain acceptable estimations.

Excess Molar Enthalpies of Ternary and Binary Mixtures Containing 2-Methoxy-2-methylpropane, 1-Propanol, and Nonane

Excess molar enthalpies for the ternary system {x1 2-methoxy-2-methylpropane (MTBE) + x2 1-propanol + (1 − x1 − x2) nonane} and the involved binary mixture {x 1-propanol + (1 − x) nonane} have been measured at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently avaliable literature for the ternary and binary mixtures under study in similar conditions. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The results were fitted by means of different variable degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The group contribution model of the UNIFAC model (in the versions of Larsen et al. and Gmehling et al.) was used to estimate ternary excess enthalpy values. Several empirical expressions for estimating ternary properties from binary results were also tested.

Study of the effect of increasing the chain length of the alkane in excess molar enthalpies of mixtures containing methyl tert-butyl ether, 1-propanol, alkane

Excess molar enthalpies for the ternary system { x 1 methyl tert-butyl ether + x 2 1-propanol + (1 − x 1 − x 2) decane} and the involved binary mixture { x 1-propanol + (1 − x) decane} have been measured at the temperature of 298.15 K and atmospheric pressure, over the whole composition range. No experimental excess enthalpy values were found in the currently avaliable literature for the ternary mixture under study. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The results were fitted by means of different variable degree polynomials. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. The group contribution model of the UNIFAC model (in the versions of Larsen and Gmehling) was used to estimate ternary excess enthalpy values. Several empirical expressions for estimating ternary properties from binary results were also tested. A study of the effect of increasing the chain length of the n-alkane is made.

Excess molar enthalpies and heat capacities of dimethyl sulfoxide + seven normal alkanols at 303.15 K and atmospheric pressure

Excess molar enthalpies and heat capacities of binary mixtures containing dimethyl sulfoxide (DMSO) + seven normal alkanols, namely methanol, ethanol, propan-1-ol, butan-1-ol, hexan-1-ol, octan-1-ol, and decan-1-ol, have been determined at 303.15 K and atmospheric pressure. With the exception of the DMSO–methanol system, which shows negative values, all mixtures show positive values of excess molar enthalpies over the whole range of mole fraction, increasing as the number of carbon atoms increases. Heat capacities of pure components have been determined in the range 288.15 < T (K) < 325.15. Molar heat capacities of the mixtures are always positive and decrease as the number of carbon atoms decreases. The results were fitted to the Redlich–Kister polynomial equation. Molecular interactions in the mixtures are interpreted on the basis of the results obtained.

Excess molar enthalpies for binary carbon dioxide + diethyl carbonate system at 298.15–308.15 K and 5.0–6.5 MPa

The excess molar enthalpies of the carbon dioxide + diethyl carbonate system were determined using a flow-type isothermal microcalorimeter at temperatures from 298.15 to 308.15 K and pressures from 5.0 to 6.5 MPa. Mixtures shows strong exothermic behavior in these regions. In addition, a strong pressure dependency of the excess molar enthalpies was observed, and the excess molar enthalpy values decreased with increasing pressure. The experimental results were correlated using a composition-dependent equation and the Peng–Robinson equation of state with the conventional mixing rule. Finally, the prediction of excess molar enthalpies using three mixing rules (MHV1, MHV2, and Wong–Sandler) was also tested on the basis of the vapor–liquid equilibrium data.

Excess Molar Enthalpies of the Binary Carbon Dioxide + Dimethyl Carbonate System at Temperatures of (298.15 to 308.15) K and Pressures of (5.0 to 7.5) MPa

The excess molar enthalpies of the carbon dioxide + dimethyl carbonate system were measured in the vicinity of the critical point of carbon dioxide using a flow-type isothermal microcalorimeter at temperatures of (298.15 to 308.15) K and pressures of (5.0 to 7.5) MPa. Mixtures showed strong exothermic behavior in these regions. In addition, a strong pressure dependency of the excess molar enthalpies was observed, and the excess molar enthalpy values decreased with increasing pressure. The experimental results were correlated using a composition-dependent equation and the Peng−Robinson equation of state with van der Waals one-fluid mixing rules.

Determination of excess molar enthalpies of the ternary system methyl tert-butyl ether + 1-pentanol + nonane at 298.15 K : Analysis and comparison with predicted values of the UNIFAC model and some empirical methods

Excess molar enthalpies for the ternary system { x 1 methyl tert-butyl ether (MTBE) + x 2 (1-pentanol) + (1 − x 1 − x 2) nonane} and the involved binary mixtures { x methyl tert-butyl ether + (1 − x) nonane} and, { x (1-pentanol) + (1 − x) nonane} have been measured at the temperature of 298.15 K and atmospheric pressure over the whole composition range. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The results were fitted by means of different variable degree polynomials. In the present work, we propose a new expression to fit the ternary excess molar enthalpy, which takes into account the asymmetric shape of the three binary systems. The group contribution model of the UNIFAC model (in the versions of Larsen and Gmehling) was used to estimate ternary excess enthalpy values. Several empirical expressions for estimating ternary properties from binary results were also tested.

Measurement and Prediction of Excess Molar Enthalpies and Excess Molar Volumes of the Ternary System 1,3-Dichlorobenzene + Benzene + Hexane at 298.15 K

Experimental excess molar enthalpies and excess molar volumes for the ternary system {x1 1,3-dichlorobenzene + x2 benzene + (1− x1 − x2) hexane} have been determined at the temperature of 298.15 K and atmospheric pressure. Values of excess molar enthalpies were measured using a Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a vibrating-tube densimeter. Several empirical expressions for estimating ternary properties from experimental binary results were applied.

Experimental enthalpies of mixtures of alkylfluoroethers + n-alkanes at 298.15 K

In this work, excess molar enthalpies, H m E, at 298.15 K and atmospheric pressure of methylnonafluorobutylether + alkane (hexane, octane, decane, dodecane) and ethylnonafluorobutylether + alkane (hexane, octane, decane, dodecane) are reported. Values of excess molar enthalpies were measured using a Calvet microcalorimeter. The binary experimental data were fitted using a Redlich–Kister variable-degree polynomial. The excess molar enthalpy is positive for all the mixtures. Phase separation is found in the range of 0.3< x<0.8 and 0.3< x<0.94 for the mixtures methylnonafluorobutyl ether + (decane, or dodecane), respectively.

Excess molar enthalpies and excess molar volumes of methyl methacrylate + benzene, + toluene, + p-xylene, + cyclohexane and + aliphatic diethers (diethyl, diisopropyl and dibutyl)

Experimental values of excess molar enthalpies ( H m E) at T=298.15 K and excess molar volumes ( V m E) at T=298.15–318.15 K for binary liquid mixtures of methyl methacrylate (MMA) + benzene, + toluene, + p-xylene, + cyclohexane and + diethers (diethyl, diisopropyl and dibutyl) are reported. The qualitative analysis of both the excess molar functions was done taking in to consideration the molecular size of ethers and the nature of the hydrocarbon. The results show that besides the weakening of dipolar forces among ester molecules, specific but weak interactions of n⋯π and dipole–dipole types are significant in these mixtures (with an exception in MMA+cyclohexane).

Excess Molar Enthalpies and Excess Molar Volumes of the Ternary System 1,2-Dichlorobenzene + Benzene + 1-Chlorohexane at 298.15 K

Excess molar enthalpies and excess molar volumes for the ternary system {(x1)1,2-dichlorobenzene + (x2)benzene + (1 − x1 − x2)1-chlorohexane} and the involved binary mixture {(x)benzene + (1 − x)1-chlorohexane} have been determined at the temperature 298.15 K and atmospheric pressure. Values of excess molar enthalpies were measured using a Calvet microcalorimeter, and excess molar volumes were determined from the densities of the pure liquids and mixtures, using a vibrating-tube densimeter. The experimental values were used to test the results obtained with empirical expressions for estimating ternary properties from binary data.

Microcalorimetric studies to determine the enthalpy of solution of diclofenac sodium, paracetamol and their binary mixtures at 310.15 K

A sensitive and selective microcalorimetric technique has been used to determine the enthalpy of solution of diclofenac sodium (DS), paracetamol (PC) and their binary mixtures over a wide range of composition in the pH range 4–12. The systems showed endothermic behavior. The molar enthalpies of solutions of DS vary between 42.26±0.16 and 50.48±0.03 kJ mol −1 at pH 4–9 and for PC from 24.28±0.05 to 36.03±0.01 kJ mol −1 at pH 5–12. The excess molar enthalpy of their mixtures has also been determined. The values of excess molar enthalpy of solutions are negative and very low in magnitude indicating no specific interaction between DS and PC in solution.