Elsevier

Fluid Phase Equilibria

Volume 276, Issue 1, 15 February 2009, Pages 53-56
Fluid Phase Equilibria

Isobaric vapor–liquid equilibria for the n-hexane + 2-isopropoxyethanol and n-heptane + 2-isopropoxyethanol systems

https://doi.org/10.1016/j.fluid.2008.09.026Get rights and content

Abstract

Vapor–liquid equilibria (VLE) for the n-hexane + 2-isopropoxyethanol and n-heptane + 2-isopropoxyethanol (at 60, 80, and 100 kPa) systems were measured. Two systems present positive deviations from ideal behavior. And the system n-heptane + 2-isopropoxyethanol shows a minimum boiling azeotrope at all pressures. Experimented data have been correlated with the two term virial equation for vapor-phase fugacity coefficients and the three suffix Margules equation, Wilson, NRTL, and UNIQUAC equations for liquid-phase activity coefficients. Experimental VLE data show excellent agreements with models.

Introduction

Surfactants are industrially important materials because of various applications in the cosmetic, pharmaceutical, and food industries. For successful usages of these materials in the process design and operation, it is essential that phase behaviors for mixtures containing nonionic surfactant systems, such as vapor–liquid equilibria and liquid–liquid equilibria are accurately measured. Ethoxylated alcohol {H-(CH2)i-(OCH2CH2)j-OH or CiEj} surfactants are a particularly interesting class of substances because that they have both ether (O) and hydroxyl (OH) groups in the one molecule. There are many phase equilibrium data for Water + surfactant [1], [2], [3], [4] measured at atmospheric pressure, but few data are available for hydrocarbon + surfactant systems (e.g. C1E1 + n-hexane, n-heptane, cyclohexane [5] or C2E1 + n-hexane, n-heptane, cyclohexane [6]).

In this study, we measured (vapor + liquid) equilibrium data for {n-hexane + 2-isopropoxyethanol (i-C3E1)} and {n-heptane + 2-isopropoxyethanol (i-C3E1)} systems at pressures ranging from 60 to 100 kPa. VLE data of binary systems were found to be thermodynamically consistent. In addition, the experimental data were correlated with using the three suffix Margules [7], Wilson [8], NRTL [9], and UNIQUAC [10] equations for the liquid phase activity coefficients.

Section snippets

Materials

n-heptane and n-hexane were supplied by Junsei Chemical (Japan) with a minimum purity of 99.5% (GC) and stored over a molecular sieve. 2-isopropoxyethanol was supplied by Aldrich (U.S.A.) with a minimum purity of 99.0% (analytical grade). We used these chemicals without further purification, because significant other peaks were not found from gas chromatography analysis.

Apparatus and procedures

Experiments were conducted using the apparatus VLE 602 of the company i-Fischer Engineering GmbH, Waldbuettelbrunn (Germany).

Results and discussion

The isobaric VLE data were measured at 60, 80, and 100 kPa. These data for the system n-hexane (1) + 2-isopropoxyethanol (2) and n-heptane (1) + 2-isopropoxyethanol (2) are listed in Table 1, Table 2. In these tables, boiling temperatures for all isobars were obtained from the Antoine equation with constants A, B and C presented in Table 3. The activity coefficient, γi was calculated byγi=yiPxiPisatexp(BiiviL)(PPisat)+(1yi)2PδijRTδij=2BijBiiBjjwhere xi and yi are the liquid and vapor-phase

Conclusions

The isobaric VLE data for n-hexane + 2-isopropoxyethanol and n-heptane + 2-isopropoxyethanol systems were obtained at 60, 80, and 100 kPa. Four activity coefficient models, namely, three suffix Margules, Wilson, NRTL, and UNIQUAC, were used for correlations. Correlation results are in good agreement with the experimental data. The system n-heptane + 2-isopropoxyethanol shows the azeotropic composition.

    List of symbols

    A

    Antoine equation constant, Eq. (3)

    Ai

    parameters of Legendre polynomial

    Aij

    the three suffix Margules

Acknowledgements

This work was supported by the Brain Korea 21 Program supported by the Ministry of Education and by the National Research Laboratory (NRL) Program supported by Korea Institute of S&T Evaluation and Planning.

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