Solubility and critical surface in the system propionic acid–ethanol–ethyl propionate–water at 293.15, 303.15 and 313.15 K
Introduction
Ethyl propionate is a commonly used chemical reagent and has areas of application such as flavoring agents, pharmaceuticals, and other industries [1], [2], [3]. Ethyl propionate is also considered as a model for fatty acid ethyl esters used as first-generation biodiesel [4]. The production of ethyl acetate is based on acid-catalyzed esterification of propionic acid with ethanol. These processes should be considered to be coupled processes of the simultaneous chemical reaction and separation of products. The complex approach of investigating of such kind of process leads to the establishment of new basic physical-chemical singularities which are also important for design of technological process of chemical synthesis.
There are extremely limited scientific works corresponds to the study of solubility, liquid-liquid (LL) and chemical equilibrium (CE) in propionic acid–ethanol–ethyl propionate–water system. First data on the solubility and critical point (plait point) in ternary ethanol–ethyl propionate–water system were obtained in 1910 by Bonner [5] at 273.15 K and atmospheric pressure using pycnometers. Mutual solubility in binary ethyl propionate–water system was carried out at 298 K in [6] by calorimetry and differential refractometry method. Some solubility data in the same system were presented by Venkataratnam, Rao et al. [7], [8], [9], [10] at 302.15–303.15 K. There are LLE data for this mixture within wide temperature range 273–353 K [11] and 293.15–353.15 K [12] and atmospheric pressure. Recommended values of mutual solubility data in ethyl propionate–water system are collected in [13].
Therefore in present work a new experimental study on solubility and critical states for quaternary propionic acid–ethanol–ethyl propionate–water system at polythermal conditions (293.15, 303.15 and 313.15 K) and atmospheric pressure was carried out. We note that in our previous paper [14] CE data are presented at 303.15 and 313.15 K and atmospheric pressure. It was shown that CE is reached both in homogeneous and heterogeneous area of composition of reactive mixture. Accordingly LLE data were obtained for the surface of CE, but solubility and critical states have not been studied in quaternary system investigated.
Section snippets
Materials
Propionic acid (>0.98 mol fraction, Vekton, Russia), ethanol (>0.96 mol fraction, Vekton, Russia) and ethyl propionate (>0.98 mol fraction, Vekton, Russia) were purified by multi-stage distillation process in form of counter-current distillation (rectification) in a column, water was distilled twice. Refractive index measurements were performed using IRF 454 BM (Russia) refractometer at 101.3 kPa (±1 kPa) and 293.15 K and provided with the temperature controlled to within ±0.05 K by circulating
Results and discussions
The results on solubility study for one binary ethyl propionate–water and two ternary subsystems propionic acid–ethyl propionate–water, ethanol–ethyl propionate–water at 293.15, 303.15 and 313.15 K and atmospheric pressure (101.3 kPa) are given in Table 2, Table 3 accordingly.
A comparative analysis of our experimental results at 293.15, 303.15 and 313.15 K on binary subsystems with available literature data [7], [9], [10], [12] collected by Getzen, Hefter and Maczynski in [13] showed a
Modeling of LLE
The calculation procedure for the prediction of LLE using UNIFAC model was based on the approach developed in [33]. In our work, the UNIFAC parameters were taken from [34]. The first step in modeling was the calculation of the coefficients of activity of components i in a multicomponent mixture according to the equation:where γiC and γiR are combinatorial segment and a residual segment of an activity coefficient accordingly.
Combinatorial segment is calculated as follows:
Conclusions
This work presents new experimental solubility data for binary (ethyl propionate–water), ternary (ethanol–ethyl propionate–water and propionic acid–ethyl propionate–water) and quaternary propionic acid–ethanol–ethyl propionate–water system at 293.15, 303.15 and 313.15 K and atmospheric pressure (101.3 kPa). In addition, the compositions of critical states are determined for quaternary system investigated under the same three temperatures. The results of calculations of solubility and LLE on the
Acknowledgments
Maria Toikka is grateful to the Russian Science Foundation (grant 17-73-10290) for the support of this study. Authors are also grateful to NIST ThermoData Engine group for the data on the properties of considered system.
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