Elsevier

Fluid Phase Equilibria

Volume 409, 15 February 2016, Pages 72-77
Fluid Phase Equilibria

Experimental and predicted vapour–liquid equilibrium of the binary mixtures n-heptane + chlorobutane isomers

https://doi.org/10.1016/j.fluid.2015.09.031Get rights and content

Highlights

  • Isothermal VLE data of the binary mixtures n-heptane + chlorobutane isomers are reported.

  • VLE data have been correlated with the Wilson equation.

  • Thermodynamic consistency of VLE data was checked by the van Ness method.

  • The calculated excess Gibbs energies were positive for all the mixtures.

  • UNIFAC and VTPR methods were used to predict the phase equilibrium.

Abstract

The study of the isothermal vapour–liquid equilibrium (VLE) of the binary mixtures n-heptane plus chlorobutane isomers (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane) at three different temperatures, T = 288.15, 298.15 and 308.15 K, is presented in this contribution. The experimental results were correlated using Wilson equation and the thermodynamic consistency of the data was checked by the van Ness method. Furthermore, two different methods have been used to predict the phase equilibrium in isothermal conditions: a pure group contribution method (modified-UNIFAC) and a group contribution equation of state (VTPR).

Introduction

The study of the phase equilibrium of binary mixtures provides information of great interest for many industrial applications, especially in separation processes like distillation or extraction. To get an accurate knowledge of the phase equilibrium it is desirable to have a reliable and complete set of experimental data. However, this kind of information is not always available and it is necessary to use prediction methods, for the development and improvement of these methods [1], [2], [3], [4], [5], [6], [7] it is necessary to dispose of a phase equilibria database as large as possible.

With the aim of increasing the vapour–liquid equilibrium database and following our systematic study on vapour–liquid equilibrium of systems containing an alkane and a chloroalkane [8], [9], [10] we present here the vapour–liquid equilibrium of the four binary mixtures n-heptane plus chlorobutane isomers (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane or 2-chloro-2-methylpropane) at T = 288.15, 298.15 and 308.15 K. These experimental vapour–liquid equilibrium data were checked for thermodynamic consistency and they were correlated using the Wilson equation [11].

Additionally, using our experimental data, two different predictions models were tested: modified-UNIFAC method and volume translated Peng–Robinson group contribution equation of state (VTPR model) that combines the VTPR equation of state with the group contribution concept.

A survey of the literature shows that there are some papers reporting the isothermal vapour–liquid equilibrium for the systems: n-heptane + 1-chlorobutane at T = 298.15 K and 323.15 K [12], and at T = 303.15 K, 323.15 K and 353.15 K [13], n-heptane + 2-chlorobutane at T = 323.15 K and 333.15 K [14], and n-heptane + 2-chloro-2-methylpropane at T = 323.15 K [14].

Section snippets

Experimental section

The information about the commercial source of the liquids used in this work, together with their purities and water contents, are shown in Table 1. The water content of the liquids was determined by using an automatic titrator Crison KF 1S–2B.

An all-glass dynamic recirculating type still equipped with a Cottrell pump has been used for the determination of the VLE. This is a Labodest model from Fischer. The equilibrium pressure is measured with a Digiquartz 735–215A–102 pressure transducer

Results and discussion

The Wilson equation [11] was used to correlate the activity coefficients, γi, with the temperature, T, and the mole fraction of liquid phase, xi.lnγ1=ln(x1+Λ12x2)+x2(Λ12x1+Λ12x2Λ21Λ21x1+x2)lnγ2=ln(x2+Λ21x1)x1(Λ12x1+Λ12x2Λ21Λ21x1+x2)Λij=VjViexp(λijλiiRT)where Vi is the molar volume of component i in the liquid phase at T = 298.15 K, (λij−λii) are the Wilson parameters, T is the absolute temperature and R is the gas constant.

Wilson parameters have been calculated by minimizing the

UNIFAC and VTPR predictions

In this work, two different methods (modified-UNIFAC and VTPR) have been used to predict the vapour–liquid equilibrium of binary mixtures n-heptane + chlorobutane isomers.

The group interaction parameters for both methods [24], [25], needed for the estimation of vapour–liquid equilibrium, are given in the Supplementary material, on the other hand all the properties of pure compounds required for the VTPR model calculations have been taken directly from Dortmund Data Bank [26] and they are also

Conclusions

The vapour–liquid equilibrium for binary mixtures containing n-heptane and chlorobutane isomers (1-chlorobutane, 2-chlorobutane, 1-chloro-2-methylpropane and 2-chloro-2-methylpropane) has been studied at three temperatures: T = 288.15, 298.15 and 308.15 K, activity coefficients and excess Gibbs energies have been obtained from experimental data. GE are positive for all the systems and at T = 298.15 K show this tendency:

Acknowledgements

Financial support from Gobierno de Aragon and European Social Fund is gratefully acknowledged (research group E54).

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