Elsevier

Fluid Phase Equilibria

Volume 227, Issue 2, 25 January 2005, Pages 239-244
Fluid Phase Equilibria

Isobaric vapor–liquid equilibria for 1-propanol + water + copper(II) chloride at 100 kPa

https://doi.org/10.1016/j.fluid.2004.11.014Get rights and content

Abstract

Isobaric vapor–liquid equilibria for the ternary system 1-propanol + water + copper(II) chloride has been measured at 100 kPa using a recirculating still. The addition of copper(II) chloride to the solvent mixture produced a salting-out effect of the alcohol, but the azeotrope did not tend to be eliminated when the salt content increased. The experimental data sets were fitted with the electrolyte NRTL model and the parameters of Mock's model were estimated. This model has proved to be suitable to represent experimental data in the entire range of compositions. The effect of copper(II) chloride on the vapor–liquid equilibrium of the 1-propanol + water system has been compared with that produced by other salts.

Introduction

The presence of a salt may have a substantial influence on the system phase equilibria. When a salt is dissolved in a mixed solvent, the non-dissociated molecules, the ions, or both interact with the solvent molecules in a very complex way, affecting the activity of the liquid-phase components. The magnitude of the interaction is influenced by the nature of the implied species and their concentration. The addition of salt to solvent mixture affects the boiling point, the mutual solubility of the two liquid components, and the relative volatility of solvents. Electrolyte solutions have been the subject of a large number of experimental and theoretical studies although, due to their complexity, electrolyte solutions still represent an important and challenging area of interest.

Whereas many data for water and salt systems exist, data for salts in solvents or their water mixtures are very sparse. In a previous paper, Vercher et al. [1] discussed the data source of these systems and the thermodynamic models for mixed-solvent electrolyte systems developed during the last three decades. From that, we concluded that more efforts in this area were necessary.

This work studies experimentally the effect of copper(II) chloride on vapor–liquid equilibrium of the 1-propanol + water system at different salt concentrations, checks the results by their correlation with the electrolyte NRTL model of Mock et al. [2], as well as comparing the salt effect of copper(II) chloride on the vapor–liquid equilibrium of the 1-propanol + water system with that produced by other salts.

The 1-propanol + water + copper(II) chloride system was only experimentally studied by Alvarez-González and Galán-Serrano [3] at saturation conditions. However, they could not attain thermodynamic studies because of the strong deviations in the system. Experimental values for this system at different salt compositions have not been found in the literature.

Section snippets

Materials

The chemicals used were 1-propanol (Merck, GR grade) with a stated minimum purity of 99.5 wt.% (maximum 0.05 wt.% water), distilled water (Merck, HPLC grade), and copper(II) chloride dihydrate (Merck, GR grade, min 99.0 wt.%). The solvents were directly used without further purification. Copper(II) chloride was dried at 453 K by heating for more than 24 h. No water was detected in the salt by an automatic water detector.

Apparatus and procedure

The equilibrium apparatus used in this work was an all-glass, dynamic

Experimental data

Vapor–liquid equilibrium for the 1-propanol (1) + water (2) + copper(II) chloride (3) ternary system has been obtained at 100 kPa and the results are reported in Table 1. In this table, x3 is the mole fraction of salt in the liquid phase, x1 the mole fraction of 1-propanol in the liquid phase expressed on a salt-free basis, y1 the mole fraction of 1-propanol in the vapor phase and T the equilibrium temperature.

Calculation of phase equilibrium

The electrolyte NRTL model used to predict the vapor–liquid equilibrium of the ternary

Conclusions

The addition of copper(II) chloride to 1-propanol + water systems produces a salting-out effect of the alcohol and the displacement of the azeotropic point towards higher x1 values. This effect is smaller than that observed for calcium nitrate [7], calcium chloride [8], lithium nitrate [1], or lithium chloride [11] on this system. On the other hand, the minimum non-azeotropic point also changes with the salt content but this variation is small and does not depend, practically, on the salt used.

Acknowledgements

The authors gratefully acknowledge the financial support of the Spain Interministerial Commission of Science and Technology (CICYT) under the Grant PPQ2000-1335.

References (11)

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There are more references available in the full text version of this article.

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