Phase equilibria measurements of ternary mixtures (sulfolane + a carboxylic acid + pentane) at 303.15 K

doi:10.1016/j.fluid.2015.06.029

Fluid Phase Equilibria

Volume 404, 25 October 2015, Pages 26-31

https://doi.org/10.1016/j.fluid.2015.06.029 Get rights and content

Highlights

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The liquid–liquid equilibrium for (sulfolane + acetic or propanoic or butanoic or 2-methylpropanoic or pentanoic or 3-methylbutanoic acid + pentane) at 303.15 K were measured.
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Selectivity values for solvent separation efficiency were calculated from the tie-line data and show that separation of carboxylic acids from pentane is feasible by extraction with acetonitrile.
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Three parameter equations have been fitted to the binodal curve data.
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The NRTL and UNIQUAC models were used to correlate the experimental data.

Abstract

The Liquid–liquid equilibrium (LLE) data for the mixtures of {sulfolane (1) + a carboxylic acid (2) + pentane (3)} at 303.15 K are reported, where a carboxylic acid refers to acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid. The shape of the binodal curves show that the solubility of pentane in (sulfolane + a carboxylic acid) is very much dependent on the carbon number and the type of carboxylic acid. The area of the two phase heterogeneous region for the carboxylic mixtures decreases in the order of acetic acid > propanoic acid > 2-methylpropanoic acid ∼ butanoic acid > pentanoic acid ∼ 3-methylbutanoic acid. Three parameter equations have been fitted to the binodal curve data. The NRTL and UNIQUAC models were used to correlate the experimental data. The NRTL model fitted the experimental data better than the UNIQUAC model with the average mean square deviation of 0.072 mole fraction as compared to 0.359 mole fraction for UNIQUAC model.

Introduction

The design and evaluation of industrial units for separation processes requires reliable phase equilibria data of the different mixtures involved in a given process. Especially, ternary liquid–liquid equilibrium (LLE) data are essential for a proper understanding of the solvent extraction process. Sulfolane is used widely in the chemical industry for the extraction of aromatic hydrocarbons [1], [2], [3], [4] and many investigators [5], [6], [7], [8], [9], [10], [11], [12], [13], [14] have studied liquid–liquid equilibria for the ternary systems containing {sulfolane + alkanes (C₅–C₈) + (benzene, toluene, or xylene)}. The main purpose of this study is to generate new LLE data for (sulfolane + acetic acid/propanoic acid/butanoic acid/2-methylpropanoic acid/pentanoic acid/3-methylbutanoic acid + pentane) at 303.15 K and to correlate data using the NRTL model of Renon and Prausnitz [15] and the UNIQUAC model of Abrams and Prausnitz [16]. These results provide information to design and evaluation of industrial units for separation processes. Best of our knowledge, there are no data available in open literature on the systems investigated in this work. The present work is a part of our comprehensive investigation on liquid–liquid equilibrium (LLE) data of ternary mixtures containing organic solvents which are useful in the chemical industry [14], [17], [18].

Section snippets

Chemicals

The carboxylic acids, namely acetic acid, propanoic acid, butanoic acid, 2-methylpropanoic acid, pentanoic acid and 3-methylbutanoic acid sulfolane and pentane were obtanied from Fluka Chemicals with mole fraction purities of ≥0.99. Analysis by Karl–Fischer technique showed that the water content was less than 0.001 mass percent for all the chemicals. Pure component specifications: suppliers, specified purity and GC purity are given in Table 1. The physical properties of the chemicals used in

Results and discussion

This paper presents the experimental LLE data for six ternary systems of {sulfolane (1) + acetic acid (2) + pentane (3)}, {sulfolane (1) + propanoic acid (2) + pentane (3)}, {sulfolane (1) + butanoic acid (2) + pentane (3)}, {sulfolane (1) + 2-methylpropanoic acid (2) + pentane (3)}, {sulfolane (1) + pentanoic acid (2) + pentane (3)} and {sulfolane (1) + 3-methylbutanoic acid (2) + pentane (3)} at 303.15 K. The measured compositions of equilibrium liquid phase of the ternary system, {sulfolane (1) + a carboxylic acid (2) +

LLE data correlation

The standard deviations, σ, of the three fitted equations to the binodal curves, namely the modified Hlavatý [22], beta and logγ have been used in this work. The three equations have been fitted to the data following the work of Hlavatý, 1972 [22].

The coefficient A_i relate to a modified Hlavatý equation: $x_{2} = A_{1} x_{A} ln x_{A} + A_{2} x_{B} ln x_{B} + A_{3} x_{A} ln x_{B}$

The coefficient B₁ relate to β function equation: $x_{2} = B_{1} {(1 - x_{A})}^{B 2} {x_{A}}^{B 3}$

The coeffiecient C₁, relate to the log γ equation: $x_{2} = C_{1} {(- ln x_{A})}^{C 2} {x_{A}}^{C 3}$ where $x_{A} = (x_{1} + 0.5 x_{2} - x_{2} - {x_{1}}^{0}) / ({x_{11}}^{0}$

Conclusions

The experimental LLE results for the six ternary mixtures of {sulfolane (1) + acetic or propanoic or butanoic or 2-methylpropanoic or pentanoic or 3-methylbutanoic acid (2) + pentane (3)} were determined at 303.15 K. Fig. 1(a–f) shows that the area of two-phase heterogeneous region for the carboxylic mixtures increases in the order: 3-methylbutanoic acid ∼ pentanoic acid < 2-methylpropanoic acid ∼ butanoic acid < propanoic < acetic acid. The mutual solubility of the components is increased as the carbon chain

Acknowledgements

The authors acknowledge funding from Department of Science, Technology and the National Research Foundation (DST/NRF) and Durban University of Technology South Africa for financial support.

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Cited by (3)

Liquid-liquid equilibria for toluene/heptane + phenol/cresols + ethylene glycol system
2017, Journal of Chemical Thermodynamics
Citation Excerpt :
The slopes of the tie lines presented in Figs. 2–7 show that phenols are more soluble in ethylene glycol than in toluene/heptane. The similar conclusion has been obtained in the mixtures of sulfolane + acarboxylic acid + pentane system [18]. The authors concluded that the carboxylic acids were more soluble in pentane-rich than in sulfolane-rich mixture according to the slopes of the tie lines.
Liquid-liquid equilibria data for the mixture of toluene/heptane + phenol, o-, m- or p-cresol + ethylene glycol were studied at 323.15 K and at 101.3 kPa. The tie lines in ternary phase diagrams indicate phenols are more soluble in ethylene glycol than in toluene/heptane. The distribution coefficient and selectivity were calculated according to the LLE data. The calculation results suggest that ethylene glycol is an available solvent for the extraction application. The root-mean-square deviation (RMSD) values of the NRTL and UNIQUAC models demonstrate that both of the two models can fit the experimental data very well.
(Liquid + liquid) equilibria measurements for ternary systems (sulfolane + a carboxylic acid + n-heptane) at T = 303.15 K and at 0.1 MPa
2016, Journal of Chemical Thermodynamics
Citation Excerpt :
Sulfolane as a solvent is a versatility due to their unique properties such as high polarity, chemically and thermally stable, recyclable, ease to handle and its low hazard characteristic [1–3]. ( Liquid + liquid) data for sulfolane with other solvents have been reported by several researchers [2,4–7]. Sulfolane is highly polar hence allowing it to be highly soluble in water, while the four carbon rings provide non-polar stability.
In the present work, new (liquid + liquid) equilibrium (LLE) values are reported for ternary systems {sulfolane(1) + acetic acid, or propanoic acid, or butanoic acid, or 2-methylpropanoic acid, or pentanoic acid, or 3-methylbutanoic acid (2) + n-heptane (3)} at T = 303.15 K and at p = 0.1 MPa. The mutual solubility of carboxylic acid in sulfolane is dependent on the length and structure of the alkyl chain of the carboxylic acid; it progressively increases with an increase in the alkyl chain of the carboxylic acid. The single phase homogenous region increases as the alkyl chain of the carboxylic acid increases. The n-heptane is most soluble in the carboxylic acid mixtures with long alkyl chain, that is, (3-methylbutanoic acid + sulfolane) and (pentanoic acid + sulfolane) systems and least soluble in the carboxylic acid with short alkyl chain (acetic acid + sulfolane) system. Carboxylic acid together with many other oxygenates and hydrocarbons are produced by SASOL Company in South Africa using the Fischer–Tropsch process. The details about this process are given in introduction section. The NRTL and UNIQUAC models were used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems. It was found that the NRTL model fits the experimental values significantly better than the UNIQUAC model.
Liquid Phase Equilibria of Aqueous Mixtures of Carboxylic Acids (C<inf>1</inf>-C<inf>4</inf>) with Ethylbenzene: Thermodynamic and Mathematical Modeling
2016, Journal of Chemical and Engineering Data

View full text

Phase equilibria measurements of ternary mixtures (sulfolane + a carboxylic acid + pentane) at 303.15 K

Highlights

Abstract

Introduction

Section snippets

Chemicals

Results and discussion

LLE data correlation

Conclusions

Acknowledgements

J. Chem. Thermodyn.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

J. Chem. Thermodyn.

Seventh World Pet. Congr. Proc.

Chem. Eng.

Handbook of Petroleum Refining Processes

J. Chem. Eng. Data

Ind. Eng. Chem. Res.

J. Chem. Eng. Data

Chem. Eng. Commun.