Vapour pressure and excess Gibbs energy of binary 1,2-dichloroethane + cyclohexanone, chloroform + cyclopentanone and chloroform + cyclohexanone mixtures at temperatures from 298.15 to 318.15 K

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Abstract

The vapour pressures of the binary systems 1,2-dichloroethane + cyclohexanone, chloroform + cyclopentanone and chloroform + cyclohexanone mixtures were measured at temperatures between 298.15 and 318.15 K. The vapour pressures vs. liquid phase composition data for three isotherms have been used to calculate the activity coefficients of the two components and the excess molar Gibbs energies, GE, for these mixtures, using Barker's method. Redlich–Kister, Wilson, NRTL and UNIQUAC equations, taking into account the vapour phase imperfection in terms of the 2-nd virial coefficient, have represented the GE values. No significant difference between GE values obtained with these equations has been observed. Our data on vapour–liquid equilibria (VLE) and excess properties of the studied systems are examined in terms of the DISQUAC and modified UNIFAC (Dortmund) predictive group contributions models.

Introduction

The design or optimization of separation processes requires new thermodynamic data regarding the behaviour of chemical systems. These data are very important also from a theoretical or fundamental viewpoint and the development of models which can predict this behaviour when experimental information is missing.

Due to their practical importance as solvents, foaming agents, refrigeration fluids and air conditioning systems, as well as because of their impact in the environment cleaning, in the last years, many studies have been made on thermodynamic properties of mixtures containing halogenated hydrocarbons.

Linear and cyclic ketones are molecules of high polarity; therefore they are expected to have strong specific interaction with chloroalkanes giving large deviations from ideal behaviour, most likely negative ones, depending not only on the solvent polarity, but also on the compounds nature and their molecular structure. In the open literature, there are only few data for systems of cyclic ketones with chloroalkanes and they are referring mostly to densities, excess volumes, excess enthalpies, relative permittivities, refractive indices and viscosities [1].

In previous papers, we have reported experimental VLE data for (cyclopentanone + 1,2-dichloroethane, +1,1,1-trichloroethane) [2], (1,1,2,2-tetrachloroethane + cyclopentanone and +cyclohexanone) [3] and (cyclopentanone + 1,3-dichloropropane, +1,4-dichlorobutane, +1-chlorobutane) [4]. The predictive ability of two group contribution models, DISQUAC and modified UNIFAC (Dormund) for cyclopentanone + chloroalkane binary mixtures have been tested and presented extensively very recently [5].

Following up our research program on measuring the vapour–liquid equilibria (VLE) in mixtures of cyclic ketones with chloroalkanes, this contribution presents VLE measurements on 1,2-dichloroethane + cyclohexanone, chloroform + cyclopentanone and chloroform + cyclohexanone, for which no such experimental data are available [6], [7].

The supplementary purpose of this work is the checking of the predictive capability (for the studied systems) of the above-mentioned two group contribution models.

To correlate the experimental VLE data, different GE models were used: Redlich–Kister [8], Wilson [9], NRTL [10], UNIQUAC [11].

Section snippets

Apparatus and procedure

The vapour pressure, P, measurements of pure compounds and binary mixtures were carried out by a static method, in which total pressure is measured as a function of the overall composition in the equilibrium cell. Use has been made of an isoteniscope based on Surovy's design [12]. The working procedure and the performance of the apparatus were described in a previous paper [13].

The equilibrium cell with a total volume of 80 cm3 is tightly connected with an Hg-filled U-tube as a null manometer

Results, correlation of experimental data and discussions

The direct experimental values, xPT, the calculated vapour phase compositions, y, and the derived thermodynamic quantities (excess Gibbs energy, GE), for the binary systems at temperatures 298.15, 308.15, and 318.15 K are presented in Table 2 and Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6. In Fig. 1, Fig. 2, Fig. 3, the experimental VLE data are presented together with those calculated by correlation with a 4th order Redlich–Kister equation; a good agreement between the data is observed.

DISQUAC model

This model, describes the properties of organic mixtures in terms of surfaces interactions, each molecule being characterized by geometrical and interaction parameters. The calculation of these parameters was presented in extent in other papers and the equations for GE and HE calculation are the same as those previously used [33], [34], [35].

In the DISQUAC model formulation, the interaction terms in the expression for the excess thermodynamic properties, contain a dispersive term (dis) and a

Conclusions

Isothermal vapour–liquid equilibrium measurements (PTx) are reported for 1,2-dichloroethane + cyclohexanone, chloroform + cyclopentanone and chloroform + cyclohexanone.

We have tested the capacity of the prediction of vapour–liquid equilibrium (VLE) and excess quantities (GE and HE) data for the studied mixtures by two group contribution models, DISQUAC and mod. UNIFAC (Do).

For the vapour–liquid equilibrium, the vapour pressures predictions of these mixtures are well represented by both models. For G

Acknowledgments

The authors acknowledge the financial support of the research grant by the Romanian Academy (GAR 57/2007). Also, the authors are grateful to Dr. H.V. Kehiaian from ITODYS, University Paris VII, CNRS, France, for initiating this research project.

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