Vapor-liquid equilibrium and excess properties of the binary mixtures formed by ethyl isobutyrate and n-alkanols
Introduction
Flavors and fragrances are faithful companions in daily life [1], [2], [3], [4]. Several of them have an ester as major component [5], [6], [7], [8]. However, the medium in which the flavor is found needs to preserve the quality and the characteristics of the molecule responsible for the scent. Therefore, the study of thermophysical properties of these esters and of its mixtures are of great importance for the design of chemical processes in which the esters are implicated. In this sense, ethyl isobutyrate is a flavoring substance [9], [10] which exists in banana, apple, wine grape, so can be found in some drinks.
In this work, we report experimental results (densities, mixing enthalpies and vapor-liquid equilibrium) for the binary systems: ethyl isobutyrate + n-alkanol (methanol, ethanol, 1-propanol or 1-butanol). Densities and mixing enthalpies were measured at two temperatures (303.15 and 323.15 K) and at atmospheric pressure (0.1 MPa). Vapor-liquid equilibrium of these mixtures was determined in two runs performed at constant temperature (303.15 and 323.15 K) and at constant pressure (40.000 and 101.325 kPa). It can be also outlined that the modified UNIFAC [11] was checked using our experimental VLE data.
To our knowledge, the properties presented here of binary mixtures involving ethyl isobutyrate and a normal alcohol at different temperatures have not been measured previously.
Section snippets
Experimental
Table 1 summarizes the information about the compounds employed in our study. With respect to the water content of the chemicals, it was determined by means of an automatic titrator Crison KF 1S-2B.
Densities of the samples, pure compounds or mixtures, were determined by means of an Anton Paar DMA 5000 vibrating tube densimeter internally thermostated at ±0.005 K. Calibration procedure can be found elsewhere [12]. The uncertainty of density measurements can be estimated in 2·10−4 g·cm−3.
The
Results and discussion
There are not previous density data at our working temperatures for ethyl isobutyrate, so no comparison is possible, with respect to experimental vapour pressures and those calculated using the data of Stull [17] the concordance is reasonable with an average deviation equals to 0.176 kPa, finally the agreement between our normal boiling point and those of the literature is really good. Regarding to the alkanols the comparison between our experimental and literature values is satisfactory, the
UNIFAC predictions
The modified-UNIFAC method has been used to predict the vapor-liquid equilibrium of the studied mixtures at the different experimental conditions, for the calculations we have employed the newest UNIFAC parameters available [79]. In Table 6 the coordinates of the UNIFAC-predicted azeotropes are shown while in Table 7 the deviations between the measured and predicted VLE data are given. The predicted azeotropic coordinates have been plotted in the corresponding Figs. The agreement between
Conclusions
This work reported experimental density data for binary mixtures containing ethyl isobutyrate with C1-C4 n-alkanols at p = 0.1 MPa, and at 303.15 and 323.15 K. From experimental data, excess molar volumes and excess molar enthalpies have been determined and correlated using Redlich-Kister polynomial expansions. Both the isothermal vapor-liquid equilibria at two temperatures (303.15 and 323.15) K and isobaric vapor-liquid equilibria at two pressures (40.000 and 101.325) kPa have been determined
Acknowledgements
Authors acknowledge the financial support from Gobierno de Aragón (grant E31_17R) Fondo de Desarrollo Regional “Construyendo Europa desde Aragón” and the Ministry of superior education and scientific research of Tunisia.
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