Vapour–liquid equilibrium and extractive distillation for separation of azeotrope isopropyl alcohol and diisopropyl ether

https://doi.org/10.1016/j.jct.2018.11.013Get rights and content

Highlights

  • 2-Ethoxyethanol and butyl acetate were selected as extractants to separate IPA and DIPE.

  • The VLE data for IPA and DIPE with extractants were measured.

  • The VLE data were correlated by the NRTL, UNIQUAC and Wilson models.

  • An extractive distillation process for separating azeotrope IPA and DIPE is proposed.

Abstract

For separation of the azeotrope isopropyl alcohol and diisopropyl ether by extractive distillation, 2-ethoxyethanol and butyl acetate were adopted as extractive solvents, and the vapour–liquid equilibrium data for the binary systems of isopropyl alcohol + 2-ethoxyethanol, isopropyl alcohol + butyl acetate, diisopropyl ether + 2-ethoxyethanol and diisopropyl ether + butyl acetate were measured at 101.3 kPa by a modified Rose type recirculating still. The Herington and van Ness consistency method were used to check the thermodynamic consistency of the VLE data. Meanwhile, the VLE data were correlated using the NRTL, UNIQUAC and Wilson models, and the binary interaction parameters of the three models were regressed. The correlation results indicate that the three models can correlate the experimental data with the root-mean-square deviation value of vapour phase mole faction less than 0.0062. Finally, an extractive distillation process for separating the azeotrope of isopropyl alcohol and diisopropyl ether is explored in this work.

Introduction

Isopropyl alcohol (IPA) is an important chemical, which is widely applied as good solvent and raw material for preparation of pharmaceuticals [1], [2], [3], [4]. Generally, isopropyl alcohol can be produced by hydration of propylene catalysed by acids [5]. During the production, diisopropyl ether (DIPE) is obtained as a byproduct, which can be used as a gasoline additive and as a solvent to extract nicotine in tobacco production [6], [7], [8], [9]. Therefore, it is of significance to separate IPA and DIPE from the reaction product. Since IPA and DIPE can form a homogeneous azeotrope at atmospheric pressure, it is difficult to separate such an azeotrope by conventional distillation. Recently, some special distillation processes, such as pressure-swing distillation and extractive distillation are adopted to separate azeotropic mixture or close boiling mixture [10].

Luo et al. explored the possibility to separate IPA and DIPE by pressure-swing distillation and extractive distillation and made a comparison [11]. In their work, the extractive distillation process shows better controllability compared with the pressure-swing distillation in maintaining the purities of IPA and DIPE with the feed flow rate disturbances, where 2-methoxyethanol was selected as extractive solvent. In this work, the extractive distillation was adopted to separate the azeotrope IPA and DIPE. Based on the extractive solvent selection criteria proposed by Gmehling and Möllmann [12], 2-ethoxyethanol and butyl acetate were selected as the extractive solvent candidates.

Up to now, the isobaric vapour–liquid equilibrium (VLE) data for the system IPA and DIPE at atmospheric pressure have been reported by Lladosa [13] and Arce [14]. Villamañãn [15] and Chamorro [16] reported the VLE data for IPA and DIPE at different pressures. By retrieving from the NIST [17] and Dortmund Data Bank [18], the isobaric VLE data for the binary systems of (IPA + 2-ethoxyethanol), (IPA + butyl acetate), (DIPE + 2-ethoxyethanol) and (DIPE + butyl acetate) have not been found.

Therefore, in this work, the isobaric VLE data for the systems (IPA + 2-ethoxyethanol), (IPA + butyl acetate), (DIPE + 2-ethoxyethanol) and (DIPE + butyl acetate) were measured at 101.3 kPa. The thermodynamic consistency of the experimental data was validated by the Herington test [19] and van Ness test [20]. The NRTL [21], UNIQUAC [22] and Wilson [23] activity coefficient models were adopted to correlate the VLE data. Based on the above, a conceptual extractive distillation process is proposed to separate the azeotrope of IPA and DIPE.

Section snippets

Chemicals

Analytical reagents IPA, DIPE, 2-ethoxyethanol and butyl acetate were purchased commercially. The purities of the reagents were checked by GC, and the reagents were used directly. The boiling temperature of the reagents were measured and compared with the literature data as listed in Table 1. The detailed information of the reagents is presented in Table 1.

Apparatus and procedure

The isobaric VLE measurements for the systems (IPA + 2-ethoxyethanol), (IPA + butyl acetate), (DIPE + 2-ethoxyethanol) and (DIPE + butyl

Validation of the apparatus

To validate the VLE measurement apparatus, the VLE data for the system {DIPE (1) + IPA (2)} were measured at pressure of 101.3 kPa, which are listed in Table 2. The measured VLE results were compared with the literature data reported by Lladosa et al. [13], Arce et al. [14], Miller et al. [41] and Zhang et al. [30], which are plotted in Fig. 1. As shown in Fig. 1, the measured VLE data agree with the literature data.

Experimental results

The isobaric VLE data for the binary systems for (IPA + 2-ethoxyethanol),

Effects of extractive solvent

Generally, the relative volatility (α12) is used to examine the suitability of the solvent and it is defined as follows [48]:α12y1/x1y2/x2where xi and yi represent the equilibrium mole fraction of component i in the liquid phase and the vapour phase, respectively.

The relative volatility diagram for the systems is presented in Fig. 8. As shown in Fig. 8, the values of relative volatility for the systems (IPA + 2-ethoxyethanol), (IPA + butyl acetate), (DIPE + 2-ethoxyethanol) and (DIPE + butyl

Conclusions

The isobaric VLE data for the systems of (IPA + 2-ethoxyethanol), (IPA + butyl acetate), (DIPE + 2-ethoxyethanol) and (DIPE + butyl acetate) were measured at 101.3 kPa. The Herington and van Ness consistency methods were used to check the thermodynamic consistency for the experimental data. Meanwhile, the NRTL, UNIQUAC and Wilson models were applied to correlate the measured VLE values, and the binary parameter of the thermodynamic models was regressed. The RMSD values of the vapour-phase

Acknowledgements

This work was financially supported by the Shandong Provincial Key Research & Development Project (2018GGX107001), the National Natural Science Foundation of China (Grant 21776145) and Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents.

References (48)

  • J.Y. Wu et al.

    Separation of azeotrope (allyl alcohol + water): Isobaric vapour-liquid phase equilibrium measurements and extractive distillation

    J. Chem. Thermodyn.

    (2018)
  • L.Z. Zhang et al.

    Measurements and correlations of density, viscosity, and vapour-liquid equilibrium for fluoro alcohols

    J. Chem. Thermodyn.

    (2016)
  • Y.C. Dong et al.

    Extractive distillation of methylal/methanol mixture using ethylene glycol as entrainer

    Fluid Phase Equilib.

    (2018)
  • Y.H. Ngo et al.

    Chemically enhanced polymer-coated carbon nanotube electronic gas sensor for isopropyl alcohol detection

    ACS Omega

    (2018)
  • J.E. Logsdon et al.

    Isopropyl alcohol Kirk-Othmer Encyclopedia of Chemical Technology

    (2000)
  • C.R. Chamorro et al.

    J. Chem. Thermodyn.

    (2007)
  • J. Soujanya et al.

    Isobaric ternary vapour-liquid equilibrium of methanol(1) + diisopropyl ether(2) + isopropyl alcohol(3) along with methanol + isopropyl alcohol binary data at atmospheric and sub-atmospheric pressures

    Fluid Phase Equilib.

    (2015)
  • J. Soujanya et al.

    Experimental isobaric vapour–liquid equilibrium at atmospheric and sub-atmospheric pressures, excess molar volumes and deviations in molar refractivity from 293.15 K to 318.15 K of diisopropyl ether with methanol and isopropyl alcohol

    Fluid Phase Equilib.

    (2014)
  • Z. Lei et al.

    Special Distillation Processes

    (2005)
  • H.T. Luo et al.

    Comparison of pressure-swing distillation and extractive distillation methods for isopropyl alcohol/diisopropyl ether separation

    Ind. Eng. Chem. Res.

    (2014)
  • J. Gmehling et al.

    Synthesis of distillation processes using thermodynamic models and the dortmund data bank

    Ind. Eng. Chem. Res.

    (1998)
  • R.M. Villamañãn et al.

    Thermodynamic properties of binary and ternary mixtures containing diisopropyl ether, 2-Propanol, and benzene at T=313.15 K

    J. Chem. Eng. Data

    (2010)
  • The NIST Bank, the National Institute of Standards and Technology, NIST....
  • J. Gmehling, U. Onken. Dortmund Data Bank (DDB), The University of Dortmund....
  • Cited by (0)

    View full text