Juan Ortega

Analysis of excess enthalpies of ester+ 1-chloroalkanes with two group contribution models: primary parameters

Abstract An analysis of the enthalpies of mixing, obtained experimentally at 298.15 K and at atmospheric pressure, of sixteen binary systems formed by four ethyl esters, from formate to butanoate, and four 1-chloroalkanes, from pentane to octane, is presented in this work. The experimental values of h E have been examined by a version of the UNIFAC model, as modified by Skjold-Jorgensen, as well as by the molecular group contribution model of Nitta. In both cases, the interaction parameters necessary for the prediction of the h E of the binary systems ester/1-chloroalkanes are determined, mainly the parameters involving the groups HCOO, COOC or COO, CH 3 or CH 2 and Cl. The predictions of h E , carried out both with the modified UNIFAC model and with the molecular model of Nitta, are similar. Thus, for the system ethyl formate+ 1-chloroalkanes, errors are lower than 6% with the UNIFAC model and less than 8% with that of Nitta. For the remaining systems, the errors increase as the chain length of the ester increases or as the h E decrease.

Thermodynamic study on binary mixtures of propyl ethanoate and an alkan-1-ol (C2–C4). Isobaric vapor–liquid equilibria and excess properties

Abstract This paper presents an analysis on binary mixtures of propyl ethanoate and an alkan-1-ol (ethanol to butanol) using the results obtained for different thermodynamic quantities such as the isobaric vapor–liquid equilibrium (VLE) data at pressures of 101.3 kPa and 160.0 kPa, excess enthalpies and excess volumes. Vapor pressures for the same normal alkanols used, determined using the same equilibrium still, are also presented. The three mixtures present expansive and endothermic effects during the mixing process. All investigated mixtures show positive deviations from ideality. For two mixtures, azeotropes are found: for propyl ethanoate+ethanol, x az =0.078, T az =351.02 K at p =101.3 kPa, while x az =0.041, T az =363.14 K at p =160.0 kPa; for propyl ethanoate+propan-1-ol, x az =0.387, T az =367.63 K at p =101.3 kPa, while x az =0.313, T az =381.02 K at p =160.0 kPa. Correlations of the activity coefficients, reduced excess Gibbs energy, and mixing enthalpy using a new equation containing temperature-dependent coefficients were good for all three binary mixtures. The ASOG and Nitta et al. models yielded the best prediction of equilibrium properties for the mixtures containing ethanol while one of the modified versions of UNIFAC model gave the best predictions of equilibrium properties for the remaining binary systems. Using the same set of parameters the UNIFAC and Nitta et al. models also yielded acceptable estimates of the excess enthalpies for the same mixtures.

Application of the UNIFAC and Nitta-Chao models to describing the behavior of methyl ester/alkane mixtures, and experimental data for (methyl n-alkanoates + n-heptadecane) binary mixtures

Abstract J. Ortega and J.L. Legido, 1994. Application of the UNIFAC and Nitta-Chao models to describing the behavior of methyl ester/alkane mixtures, and experimental data for (methyl n-alkanoates+n-heptadecane) binary mixtures. Fluid Phase Equilibria, 95: 175-214. Excess molar properties, hE and vE, were determined based on the composition of binary mixtures of fourteen methyl esters (from ethanoate to n-pentadecanoate) and n-heptadecane at 298.15 K. The results showed all the mixtures to be endothermic and to undergo positive changes in excess volume. Both these effects decreased in a quasi-regular manner with the chain length of the methyl alkanoate. The excess enthalpies of the mixtures were compared with the values estimated by two group-contribution models, two different versions of the UNIFAC model, and the model of Nitta et al. [Nitta, T., Turek, E.A., Greenkorn, R.A. and Chao, K.C., 1977. A group contribution molecular model of liquids and solutions. AIChE J., 23: 144-160]. Using the UNIFAC model, the best prediction was achieved when all the methyl esters were considered to be alkyl ethanoates, which yielded a mean overall error of less than 5%. Application of the model of Nitta et al. to the mixtures considered yielded hE and vE values that differed substantially from the experimental values, with mean overall errors of 14% for the hE values and 34% for the vE values. Therefore, a comprehensive database of thermodynamic quantities for 368 binary mixtures was used to recalculate the alkane-ester interaction parameters and group parameters, which were then reapplied in the above-mentioned molecular model. This substantially improved the estimates of the properties for the pure components as well as those for the mixing quantities, achieving mean errors of less than 4% for hE and 17% for vE.

Excess molar enthalpies of methyl alkanoates + n-nonane at 298.15 k

Abstract Microcalorimetric measurements of excess enthalpies were carried out over the whole concentration range for mixtures of nine methyl alkanoates (from acetate to decanoate) with n -nonane at 298.15 K. From these data, information could be obtained about the interactions between both chemical species. All show positive excess molar enthalpies which decrease with increasing length of the aliphatic chain of the methyl alkanoate.

Thermodynamic Behavior of the Binaries 1-Butylpyridinium Tetrafluoroborate with Water and Alkanols: Their Interpretation Using 1H NMR Spectroscopy and Quantum-Chemistry Calculations

Here we present experimental data of different properties for a set of binary mixtures composed of water or alkanols (methanol to butanol) with an ionic liquid (IL), butylpyridinium tetrafluoroborate [bpy][BF(4)]. Solubility data (x(IL),T) are presented for each of the mixtures, including water, which is found to have a small interval of compositions in IL, x(IL), with immiscibility. In each case, the upper critical solubility temperature (UCST) is determined and a correlation was observed between the UCST and the nature of the compounds in the mixtures. Miscibility curves establish the composition and temperature intervals where thermodynamic properties of the mixtures, such as enthalpies H(m)(E) and volumes V(m)(E), can be determined. Hence, at 298.15 and 318.15 K these can only be found with the first four alkanols. All mixing properties are correlated with a suitable equation ξ (x(IL),T,Y(m)(E) = 0. An analysis on the influence of the temperature in the properties is shown, likewise a comparison between the results obtained here and those of analogous mixtures, discussing the position of the -CH(3) group in the pyridinic ring. The (1)H NMR spectra are determined to analyze the molecular interactions present, especially those due to hydrogen bonds. Additional information about the molecular interactions and their influence on the mixing properties is obtained by quantum chemistry calculations.

Determination and algebraic representation of volumes of mixing at 298.15 K of methyl n-alkanoates (from ethanoate to n-pentadecanoate) with n-pentadecane

Abstract Ortega J. and Alcalde R., 1992. Determination and algebraic representations of volumes of mixing at 298.15 K of methyl n-alkanoates (from ethanoate to n-pentadecanoate) with n-pentadecane. Fluid Phase Equilibria, 71: 49-62. The present paper sets out the excess volumes, νE, for binary mixtures composed of one of fourteen methyl esters, from ethanoate to n-pentadecanoate, and n-pentadecane calculated indirectly from density value measurements carried out at 298.15 K and normal atmospheric pressure. All the mixtures presented νE > 0 which decreased in a quasi-regular manner as the chain length of the methyl ester increased. The correlation of the experimental νE values with concentration was calculated using an appropriate polynomial equation which yielded excellent results. Development of the equation is also discussed.

Experimental VLE at 101.32 kPa in binary systems composed of ethyl methanoate and alkan-1-ols or alkan-2-ols and treatment of data using a correlation with temperature-dependent parameters

Abstract New experimental VLE data of five binary ethyl methanoate+alkan-1-ol or +alkan-2-ol mixtures are presented which have been obtained isobarically at 101.32 kPa using a dynamic equilibrium apparatus. All systems verify the thermodynamic consistency with one version of the point-to-point test and present a positive deviation from ideality in almost all concentration range. Several equations are used in the treatment of VLE data, and a new correlation employed in this work using temperature-dependent coefficients appear to be also suitable. Activity coefficients calculated from experimental data have been compared with predictions of several group contribution models giving place to a mean error less than 7%. The azeotrope experimentally detected in the mixture ethyl methanoate(1)+ethanol(2) at x 1 =0.956, T =327.2 K was also well predicted by the versions used of UNIFAC.

Experimental study of miscibility, density and isobaric vapor-liquid equilibrium values for mixtures of methanol in hydrocarbons (C5, C6)

Abstract Isobaric vapor-liquid equilibrium data at 141.3 kPa for the mixtures of methanol with n-pentane and n-hexane are reported. The miscibility of methanol + n-hexane is also measured in order to get the UCSP (upper critical solubility point), then the experimental curves of vE are obtained at temperatures with total miscibility. The equilibrium data are correlated with different equations and the prediction carried out using different group-contribution models is acceptable in all cases.

Isobaric expansivities of the binary mixtures C3H7(OH) + CnH2n + 2 (n = 11, 12) between 288.15 and 318.15 K

Abstract Densities and refractive indices of the binary mixtures of propan-1-ol with n-undecane and with n-dodecane at 288.15, 298.15, 308.15 and 318.15 K have been determined as a function of the concentration of the n-alkanol. The results were employed in order to determine the mean thermal expansion coefficients, both of the pure compounds and of their mixtures by using, on the one hand, the basic expression α= −(∂ ln ϱ/∂t)p and, on the other, certain empirical expressions arising from the definitions of specific refraction given by Gladstone and Dale, Lorentz and Lorenz and Eykman. The results obtained for αE are also discussed.

Studies on densities and viscosities of binary mixtures of alkyl benzoates in N-heptane

Abstract Densities and viscosities have been determined for the two binary mixtures of methyl and ethyl benzoate in n-heptane at different concentrations and temperatures. The corresponding excess properties and the activation magnitudes were also calculated from the experimental data. All excess properties, including the excess Gibbs free energy of activation of flow, are negative over the entire range of compositions. The results for these binary mixtures are compared with those for methyl benzoate with n-nonane, the molecular interactions occurring in the mixtures being explained on the basis of the deviation from ideality of the magnitudes studied.