Elsevier

Fluid Phase Equilibria

Volume 296, Issue 1, 15 September 2010, Pages 42-45
Fluid Phase Equilibria

Liquid–liquid equilibrium of (water + 1-propanol + 1-pentanol) system at 298.15 and 323.15 K

https://doi.org/10.1016/j.fluid.2010.02.026Get rights and content

Abstract

Liquid–liquid equilibrium data for the ternary system water + 1-propanol + 1-pentanol have been determined experimentally at 298.15 and 323.15 K using “static–analytic” apparatus involving ROLSI™ samplers. The experimental data are correlated considering both NRTL and UNIQUAC activity coefficient models. The results obtained show the ability of both models for the determination of liquid–liquid equilibrium data of the studied system. The reliability of the experimental tie-line data is determined through the Othmer–Tobias and Bachman equations.

Introduction

Liquid–liquid equilibria (LLE) investigations for a wide variety of systems are still topics of great interest. The development of effective methods for the correlation or prediction of equilibrium data is essential for the design of separation units and the optimization of working conditions [1]. In fact many research works [2], [3], [4], [5] have considered multi-component systems in order to understand their phase behavior, calculate their thermodynamic properties and hence represent the equilibrium state.

Just in recent years there has been a growing interest in the separation of compounds which form a minimum boiling azeotrope such as the mixture of 1-propanol and water [6], [7] which is considered again in the present study. A good separation of 1-propanol from aqueous solutions can rather be achieved by means of a liquid–liquid extraction which is one of the most important operation unit used in chemical engineering. Thus ternary phase diagrams containing (water + 1-propanol) with solvent are needed to design the liquid–liquid contactor and to find the optimized operating conditions.

The aim of the present work is to measure LLE for the ternary system: water + 1-propanol + 1-pentanol at two different temperatures (298.15 and 323.15 K) in order to estimate the effect of this parameter change and then correlate the obtained data using NRTL [8] and UNIQUAC [9] models. Also, the new LLE data are correlated with the Othmer–Tobias [10] and Bachman [11] equations to test their reliability.

Section snippets

Chemicals

The chemicals used in this work were supplied as follows: 1-propanol by Prolabo with stated purity higher than 98 vol.%, 1-pentanol by Sigma Aldrich with a stated purity higher than 99 vol.%. Chemicals have been used without further purification, ultra pure water was prepared locally in the laboratory using commercial equipment (Millipore™, model: direct Q5). The densities and refractive indices of pure components were measured at 293.15 K and atmospheric pressure and compared to literature data

Experimental “liquid–liquid” equilibrium data

The experimental LLE data of the ternary system (water + 1-propanol + 1-pentanol) at 298.15 and 323.15 K are compiled in Table 3. The superscripts ‘I’ and ‘II’ represent the aqueous and the organic phases, respectively. Fig. 2 in which these experimental data are plotted shows that the immiscibility region shrinks slightly as temperature rises from 298.15 to 323.15 K.

Empirical treatment of data

The reliability of the obtained experimental tie-line data can be ascertained by applying the Othmer–Tobias and Bachman correlations

Conclusion

An experimental study of the LLE data of the ternary system composed of water + 1-propanol + 1-pentanol was carried out at different temperatures of 298.15 and 323.15 K using “static-analytic” method. Experimental uncertainties on the mole fractions were estimated to be within ±2.5%.

The technique with pressurization and use of ROLSI™ sampler-injector was validated for further works at higher temperatures and mixtures with at least one component having very high volatility.

The equilibrium data of the

List of symbols

    a, b

    parameters of the Othmer–Tobias and Bachman correlations

    A

    interaction parameters of NRTL and UNIQUAC models/cal mol−1

    F

    objective function

    N

    number of tie-lines

    q

    area surface parameter in UNIQUAC equation

    r

    volume parameter in UNIQUAC equation

    R2

    sample correlation coefficient

    RMSD

    root-mean square deviation

    T

    Temperature/K

    x

    mole fraction

    Greek letter

    α

    non-randomness parameter in the NRTL model

    Subscripts

    1

    water

    2

    1-propanol

    3

    1-pentanol

    i

    component

    j

    phase

    k

    tie-line

    ij

    interaction of ij pair

    ji

    interaction of ji pair

    Superscripts

    I

    aqueous phase

    II

    organic

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