Elsevier

Fluid Phase Equilibria

Volume 466, 25 June 2018, Pages 14-18
Fluid Phase Equilibria

Isobaric vapor-liquid equilibrium for chloroform + ethanol + 1,3-dimethylimidazolium dimethylphosphate at 101.3 kPa

https://doi.org/10.1016/j.fluid.2018.03.015Get rights and content

Abstract

In this study, isobaric vapor-liquid equilibrium (VLE) data for ternary systems of chloroform + ethanol + 1,3-dimethylimidazolium dimethylphosphate ([MMim][DMP]) were measured with a modified Othmer still at 101.3 kPa. VLE data were correlated with the nonrandom two-liquid (NRTL) model and the fitted results showed that [MMim][DMP] produced a crossover effect between salting-in and salting-out on chloroform. Moreover, the minimum concentration of [MMim][DMP] needed to break the azeotrope of the chloroform + ethanol system was 0.058 (mole fraction). In the current work, the effects of [MMim][DMP] were analyzed and compared with that of other ionic liquids (ILs), and [MMIM][DMP] found to be an effective candidate entrainer.

Introduction

In recent years, the separation of binary azeotropic systems containing low-carbon alcohol has become a hot topic. Chloroform and ethanol are important organic solvents, with wide applications in the pharmaceutical and chemical industries [1]. The mixture of chloroform and ethanol at 101.3 kPa can form an azeotrope, which is difficult to efficiently separate by ordinary distillation. At present, common methods for separating azeotropes include azeotropic, extractive, and pressure distillation, among which extractive distillation is a generally applied method for breaking the azeotropic point of azeotropes. In addition, organic solvents and solid salts are commonly used as entrainers [2].

Ionic liquids are potential entrainers for separating azeotropes [[3], [4], [5], [6], [7], [8]]. As a new type of green solvent, ILs have wide temperature ranges, low vapor pressure, and good thermal stability [[9], [10], [11], [12]]. These advantages have identified ILs as potential entrainers as substitutes for organic solvents and solid salts. As ILs are widely applied in extractions and azeotrope separations, VLE data regarding ILs are essential for understanding the separation rule regarding ILs as well as for developing a thermodynamic model of VLE [[13], [14], [15], [16]].

In this work, the VLE data for the binary system chloroform + ethanol and ternary systems containing [MMim][DMP] were obtained at 101.3 kPa. The effects of [MMim][DMP] on the chloroform + ethanol system were discussed and its separation ability discussed compared with other recently studied ILs.

Section snippets

Chemicals

The chemicals used in this study included chloroform, ethanol and [MMim][DMP] (Table 1). Both chloroform and ethanol (>99.9%, mass fraction) were obtained from Beijing Chemical Works (Beijing, China) and purity checked by gas chromatography (GC). The IL [MMIM][DMP] (>99%, mass fraction) was supplied by Shanghai Cheng Jie Chemical Co. Ltd.(Shanghai, China) and also purity checked by GC analysis. The water mass fractions, assessed using the Karl Fischer titration (KF), for chloroform, ethanol,

Experimental data

The activity coefficient (γi) and relative volatility (α12) was introduced to explore the effects of different ILs on chloroform + ethanol azeotropes. Considering the vapor phase ideal, the equations of γi and α12 are shown as follows:γi=yiPxiPiSα12=y1/x1y2/x2=γ1P1Sγ2P2Swhere xi and yi represents the component i mole fraction in the liquid and vapor phase, respectively, Pis the component i vapor pressure, which was calculated by Antoine equation [22,23], and P the system pressure (101.3 kPa).

Conclusion

VLE data for the binary system chloroform + ethanol and the ternary system of chloroform + ethanol + [MMim][DMP] were measured at 101.3 kPa. Addition of [MMim][DMP] broke the azeotrope, which removed the azeotropic point at a mole fraction of 0.058. Using the NRTL model, the results were correlated, which were in good agreement with the experimental results. At the same time, the NRTL model parameters of the ternary system were obtained, which had a certain reference value for process

Acknowledgements

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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