Determination and correlation of liquid–liquid equilibria for the (water + carboxylic acid + dimethyl maleate) ternary systems at T = 298.2 K

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Abstract

(Liquid–liquid) equilibrium (LLE) data for the ternary systems of {water + carboxylic acid (formic, acetic, propionic or butyric acid) + dimethyl maleate} were measured at T = 298.2 K and atmospheric pressure. Selectivity values for solvent separation efficiency were derived from the tie-line data. A comparison of the extracting capabilities of the solvent was made with respect to distribution coefficients, separation factors, and solvent-free selectivity bases. The reliability of the data was ascertained from Othmer–Tobias plots. The experimental data were correlated using the UNIQUAC and NRTL (α = 0.2) equations, and the binary interaction parameters were reported. The phase diagrams for the ternary mixtures including both the experimental and calculated tie-lines were presented.

Introduction

The efficient separation of organic acids from aqueous solutions is of economic importance in the chemical industry, for example, in the fermentation industry and many solvents have been tried and tested to improve such recovery [1], [2], [3], [4], [5], [6], [7], [8]. In this work, dimethyl maleate is used as a solvent in the separation of carboxylic acids from water. Phase equilibrium data of the aqueous mixtures with solvent are fundamentally important for simulation and design of the separation processes.

The phase compositions of the two coexistent liquid-phases were measured at 298.2 K. The objective of this work is to determine LLE data of {water (1) + formic or acetic or propionic or butyric acid (2) + dimethyl maleate (3)} at 298.2 K and atmospheric pressure. Complete phase diagrams were obtained by solubility and tie-line data simultaneously for each acid. No data on these ternary systems have been found in the literature. The experimental data have been correlated by means of the UNIQUAC [9] and NRTL [10] equations.

Section snippets

Chemicals

All chemicals used in this work (mass fraction purity > 0.99) were supplied by Merck and were used without further purification. The purity of these materials was checked by gas chromatography. Deionised water was further distilled before use. The densities and refractive indices of pure components were measured and compared with the literature [11] at 298.2 K and atmospheric pressure.

The densities were measured using a temperature controlled Anton Paar DMA 4500 density meter with an accuracy of ±1

Results and discussion

The compositions of mixtures on the binodal curve, as well as the mutual binary solubilities of water and dimethyl maleate at T = 298.2 K are given in Table 2, in which xi denotes the mole fraction of the ith component. Also, the experimental tie-line data of (water + formic acid + dimethyl maleate), (water + acetic acid + dimethyl maleate), (water + propionic acid + dimethyl maleate), and (water + butyric acid + dimethyl maleate) at T = 298.2 K were reported in Table 3, in which xiI and xiII refer to mole fraction

Conclusion

The experimental LLE data of (water + formic acid + dimethyl maleate), (water + acetic acid + dimethyl maleate), (water + propionic acid + dimethyl maleate), and (water + butyric acid + dimethyl maleate) are determined at T = 298.2 K and atmospheric pressure. Each ternary system exhibits type-1 behavior of LLE. Acetic acid has higher separation factors, compared to other three acids. The separation factors (S) and slopes of tie-lines indicated that dimethyl maleate used in this study, may serve as adequate

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