Thermophysical and volumetric study of mixtures {p-cymene + propan-1-ol} at several temperatures and atmospheric pressure. Modeling with COSMO-RS
Graphical abstract
Introduction
The thermodynamic study of binary mixtures of short chain alkanols such as ethanol or propan-1-ol with the main component of a vegetable extract results interesting for the design of extraction processes with supercritical CO2 as those alkanols are added as cosolvents to CO2 for increasing the polarity of the final solvent [1]. For this reason, in an earlier paper [2] we reported values of isobaric heat capacities and densities at atmospheric pressure for the binary mixtures of p-cymene with ethanol. In this respect, it would be interesting to extend these studies to the mixture of p-cymene with propan-1-ol.p-Cymene (1-methyl-4-(1-methyl-ethyl)benzene) is a monocyclic monoterpene that is present in volatile oils from over 100 vegetal species being a major component in the extracts of certain plants such as cumin and thyme. p-Cymene also occurs naturally in more than 200 foodstuffs, such as orange juice, grapefruit, carrots, raspberries, butter, nutmeg, tangerine, oregano, and most any other spice [3]. At present the main economic importance of this compound lies in its use as an intermediate in the industrial syntheses of fragrances, flavours, herbicides and, principally, pharmaceuticals. Besides, some studies have recently proven that p-cymene possesses antinociceptive as well as anti-inflammatory activity [4], a fact which can widen its field of applications.
In addition to the interest of thermodynamic properties for the extraction processes mentioned above, there are several studies in the literature about the thermodynamic behavior of binary mixtures of an alkanol with alkylbenzenes. So, for binary mixtures of propan-1-ol with benzene or alkylbenzenes (toluene or cumene or xylene isomers) excess molar enthalpies [5], [6], [7], [8], [9], [10], [11], [12], [13], excess molar volumes [6], [14], [15], [16], [17], [18], [19], [20], [21], [22], excess molar Gibbs energies [5], [9] and isobaric molar heat capacities [9] have been determined. New data for the mixture of p-cymene with propan-1-ol would provide a more complete knowledge about this kind of mixtures.
Therefore, in this work values of experimental isobaric molar heat capacities for the binary mixtures of p-cymene with propan-1-ol, at four temperatures (298.8, 308.7, 318.6 and 328.5) K and atmospheric pressure over the entire composition range are reported. Besides, densities have been measured at (298.15, 308.15, 318.15 and 328.15) K and atmospheric pressure also over the entire composition range. Then, excess molar volumes and excess molar heat capacities have been calculated for the mixture. The solvation model COSMO-RS [23], [24], [25] has been applied in order to evaluate its ability to predict the excess molar heat capacity. In this way useful information would be added for practical purposes as well as for basic knowledge of mixtures of alkylbenzene with alkanol.
Section snippets
Materials
The chemicals used were p-cymene and propan-1-ol. Also, water (milliQ quality) was used to perform the measurements. Their descriptions are shown in Table 1. Experimental values of density for the pure components at the working temperatures are reported in Table 2 and compared with available bibliographic values [26], [27], [28], [29], [30], [31], [32]. In general, a good agreement can be observed between both sets of data. As pointed out in a previous paper [2] for p-cymene there are
Results and discussion
Experimental values of densities, in the entire composition range, for the mixture {p-cymene (1) + propan-1-ol (2)} are reported in Table 3.
Excess molar volumes, were obtained from these densities by means of the equationbeing xi the mole fraction of pure component i and their values appear represented in Fig. 1. The estimated expanded uncertainty (k ≈ 2) for is ±0.008·106 m3·mol−1. This excess quantity was fitted to the Redlich–Kister equation
Conclusions
The molar heat capacity at atmospheric pressure of the mixture {p-cymene (1) + propan-1-ol (2)} has been determined in the temperature interval (298.8–328.5) K and the whole composition range. Densities have been also experimentally measured for the mixture in the same temperature interval for the entire composition range. From densities and molar heat capacity data, the excess molar volumes and the excess molar heat capacities have been calculated, respectively. Excess molar volumes are
Acknowledgements
The authors are grateful for the financial support of MINECO-FEDER (Project CTQ2015-64049-C3-2-R) and of Departamento de Ciencia, Tecnología y Universidad del Gobierno de Aragón-Fondo Social Europeo (Grupo E52).
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