(Vapour + liquid + liquid) equilibria and excess molar enthalpies of binary and ternary mixtures of isopropanol, water, and propylene

doi:10.1016/j.jct.2007.12.002

The Journal of Chemical Thermodynamics

Volume 40, Issue 4, April 2008, Pages 537-548

https://doi.org/10.1016/j.jct.2007.12.002 Get rights and content

Abstract

A static VLE apparatus has been used for the measurement of the (vapour + liquid + liquid) equilibrium of the (propylene + isopropanol + water) system at T = 313.15 K and pressures between (1.381 and 1.690) MPa. Using an isothermal flow calorimeter, $H^{E}$ values have been obtained for the binary system (isopropanol + water) over the temperature range from (313.15 to 353.15) K and pressures from (3.8 to 4.19) MPa. For the pseudo-binary mixture (propylene + (isopropanol + water)), $H^{E}$ values have been measured in the temperature range from (313.15 to 353.15) K and pressures from (1.997 to 5.89) MPa. This last mixture was studied starting from (isopropanol + water) at 0.25, 0.50, and 0.75 molar compositions in isopropanol. The new data, together with the available phase equilibrium and $H^{E}$ data from the literature, have been regressed by a conventional $G^{E} – EoS$ model reaching satisfactory results, except for the VLLE representation.

Introduction

A relevant part of the energy consumption in the process industries is due to the separation processes of fluid mixtures, as in the case of many productions of the chemical industry. Besides the conventional industrial separation processes, there is a raising need toward studying alternative methods compatible with the requirements of sustainable development, environmental impact and energy saving.

The limited knowledge of the thermodynamics of complex systems, starting for instance from the ternary mixtures of polar components, hinders the possibility of analysis and optimization studies of the production processes with respect to both the overall effectiveness and the energetic consumption.

Dealing with separation processes, the recovery of oxychemicals from aqueous solutions has received increasing consideration during the last decade, even if the literature is still fragmented and incomplete for the cited purpose. To proceed, it is then suggested to start choosing a system to develop an exemplifying study. After the literature search, the isopropyl alcohol (IPA) dehydration, using propylene as solvent, seems a suitable system for this study. The system (IPA + water) forms an azeotrope [1] preventing the IPA separation through conventional distillation. On the other hand, IPA has important industrial applications as raw material in paint and ink products and as solvent in electronics and in medicine.

The (propylene + isopropanol + water) system is thermodynamically strongly deviating from ideal behaviour due to several causes as the strong polarity of the components, their association behaviour, etc., which increases a lot the difficulties of a complete and accurate thermodynamic representation. Moreover, the literature is quite lacking of thermodynamic experimental data so that the foreseen study has necessarily to start from an experimental activity.

The available experimental data are concerning phase equilibria and in particular they refer to the works of Zabaloy et al. [2] and Rojas et al. [3] for VLE and LLE, respectively. Solubility data are also available from Wu et al. [4]. In this work, VLLE data for the ternary mixture and $H^{E}$ data for the psuedo-binary [propylene + (isopropanol + water)] and the binary (isopropanol + water) system have been measured.

The data have been correlated for the ternary mixture, including the binary ones, using a $G^{E} – EoS$ model with satisfactory results.

Section snippets

Materials

Water (H₂O, molar mass $M = 18.0153 kg \cdot {kmol}^{- 1}$ , CAS-RN 7732-18-5) was distilled twice. The isopropanol (CH₃CH(OH)CH₃, molar mass $M = 60.0959 kg \cdot {kmol}^{- 1}$ , CAS-RN 67-63-0) was obtained from Carl Roth firm. Its final purity after drying over molecular sieve, degassing, and distillation was 0.9995 mass% (checked by gas chromatography). The propylene (CH₃CH double bond CH₂, molar mass $M = 42.0806 kg \cdot {kmol}^{- 1}$ , CAS-RN 115-07-1) was obtained from Messer Griesheim with a purity of 0.995 mass% (checked by gas chromatography) and

Equilibrium results

The VLLE measurements have been carried out at T = 313.15 K for eight pressures from (1.381 to 1.690) MPa and they are presented in table 1. The composition of the vapour phase has been measured only in four cases, see vapour phase columns in the table, even if the vapour phase presence was optically detected for all the cases. The compositions are reported as mole fractions. The composition of the gas phase has not been measured for some of the cases because the quantity of the gas phase in the

Modelling methods

The experimental data were correlated with the Peng–Robinson [10] (PR) cubic equation of state (EoS): $P = \frac{RT}{v - b} - \frac{a (T)}{v (v + b) + b (v - b)},$ where P, T, v, and R are pressure, temperature, molar volume, and universal gas constant, respectively, while a and b are mixture parameters calculated using the Wong–Sandler [11] (WS) mixing rules. These rules are defined as $b = \frac{1}{D} \sum_{i} \sum_{j} x_{i} x_{j} E_{ij},$ $E_{ij} = \frac{1}{2} (b_{i} - \frac{a_{i}}{RT} + b_{j} - \frac{a_{j}}{RT}) (1 - k_{ij}),$ $D = 1 + \frac{G^{E}}{0.62323 RT} - \sum_{i} x_{i} \frac{a_{i}}{b_{i} RT},$ $a = bRT (1 - D),$ where $k_{ij}$ is the conventional binary interaction parameter to

Discussion

The behaviour of the $G^{E} – EoS$ model with respect to the experimental data falling inside the validity range of the present model has been studied and a statistical analysis of the data representation is reported in the following. In such context the deviation in the composition of the coexisting phases is calculated as $Δ_{j} = z_{j}^{exp} - z_{j}^{calc},$ where $z_{j}$ represents the mole fraction of the $j th$ component in the liquid or vapour phases (indicated either as $x_{j}$ or as $y_{j}$ ); in these cases the absolute average

Conclusions

VLLE values for the (propylene + isopropanol + water) system have been measured at T = 313.15 K over the pressure range from (1.381 to 1.690) MPa and $H^{E}$ measurements for the pseudo-binary mixture [propylene + (isopropanol + water)] have been obtained over the temperature range from (313.15 to 353.15) K and pressures from (1.997 to 5.89) MPa.

The ternary mixture was studied starting from the (isopropanol + water) system at the three molar compositions of 0.25, 0.50, and 0.75 in isopropanol. Furthermore, for the

Acknowledgements

The authors are grateful to the European Community Commission for financing this research by supporting Maurizio Grigiante and the Department of Industrial Chemistry of the University of Oldenburg with a Marie-Curie (EIF) fellowship.

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The Journal of Chemical Thermodynamics

(Vapour + liquid + liquid) equilibria and excess molar enthalpies of binary and ternary mixtures of isopropanol, water, and propylene

Abstract

Introduction

Section snippets

Materials

Equilibrium results

Modelling methods

Discussion

Conclusions

Acknowledgements

J. Supercrit. Fluids

Fluid Phase Equilibr.

Fluid Phase Equilibr.

J. Chem. Thermodyn.

Fluid Phase Equilibr.

Azeotropic Data, 3 Parts

J. Chem. Eng. Data

Chem. Eng. (China)

J. Chem. Eng. Data