Elsevier

Fluid Phase Equilibria

Volume 258, Issue 2, 15 September 2007, Pages 131-139
Fluid Phase Equilibria

Vapor–liquid equilibria for binary and ternary mixtures of ethanol, 2-butanone, and 2,2,4-trimethylpentane at 101.3 kPa

https://doi.org/10.1016/j.fluid.2007.06.005Get rights and content

Abstract

Vapor–liquid equilibrium (VLE) at 101.3 kPa have been determined for the ternary system ethanol + 2-butanone + 2,2,4-trimethylpentane (isooctane) and its constituent binary systems: ethanol + 2,2,4-trimethylpentane, ethanol + 2-butanone, and 2-butanone + 2,2,4-trimethylpentane. Minimum boiling azeotropes were observed for all these binary systems. No azeotropic behavior was found for the ternary system. Thermodynamic consistency tests were performed for all VLE data. The activity coefficients of the binary mixtures were satisfactorily correlated with the Wilson, NRTL, and UNIQUAC models. The models with their best-fitted binary parameters were used to predict the ternary vapor–liquid equilibrium.

Introduction

Certain oxygenated compounds are usually added to gasoline in order to improve the octane number and reduce pollution. This work has been carried out as part of a project to study the thermophysical behavior of liquid mixtures including oxygenated compounds and hydrocarbon liquids. The present paper is concerned with an experimental determination of vapor–liquid equilibrium (VLE) for a system formed by two oxygenated compounds as well as a hydrocarbon liquid. Such data of oxygenated mixtures are important for predicting the vapor phase composition that would be in equilibrium with different hydrocarbon liquids.

For these reasons, we measured VLE data for the ternary system (ethanol + 2-butanone + 2,2,4-trimethylpentane) and its constituent binary systems at 101.3 kPa. Ethanol was chosen for the present study because except for its elevated octane number, it is an important blending agent in the formulation of gasoline. 2-Butanone is used as solvent and is a possible candidate as a blending agent for reformulated gasoline. The third added compound, 2,2,4-trimethylpentane, represents the hydrocarbons in the gasoline. In the open literature there is isobaric equilibrium data for the binary systems: ethanol + 2-butanone (at 760 mmHg or atmospheric pressure) [1], [2] and ethanol + 2,2,4-trimethylpentane at 101.3 kPa [3]. As far as we know, no isobaric VLE data are available for the binary system 2-butanone + 2,2,4-trimethylpentane and the ternary system ethanol + 2-butanone + 2,2,4-trimethylpentane.

Section snippets

Chemicals

The chemicals used were of analytical grade. 2,2,4-Trimethylpentane (>99.5 mass%) was obtained from Tedia (U.S.A.). Ethanol (>99.9 mass%) and 2-butanone (>99.9 mass%) were obtained from Merck (Germany). All chemicals were used without further purification after gas chromatography failed to show any significant impurities. Before measurements the liquids were dried over molecular sieves (Merck, type 0.3 nm pellets). The purity of solvents was further ascertained by comparing their boiling points,

Experimental results

The VLE data for three binary systems of ethanol + 2-butanone, ethanol + 2,2,4-trimethylpentane, and 2-butanone + 2,2,4-trimethylpentane at the pressure of 101.3 kPa are presented in Table 2, Table 3, Table 4, respectively. The activity coefficients of pure liquid i (γi) were calculated from the equality of component fugacity in both liquid and vapor phase under the assumptions of an ideal vapor phase and an unity in the Poynting factor, i.e.γi=yiPxiPi°where xi and yi are the liquid and vapor mole

Conclusion

Isobaric VLE data were determined experimentally for the systems composed of ethanol, 2-butanone, and 2,2,4-trimethylpentane at 101.3 kPa. All systems exhibited a positive deviation from ideal behavior. A minimum boiling azeotrope occurred for all three binary systems. Azeotropic behavior was not found for the ternary system and this was confirmed by the azeotropic rule of Dorherty and Perkins. The activity coefficients of pure liquids were derived from the modified Raoult's law.

The

Acknowledgements

The authors wish to extend their deep gratitude for the support by the National Science Council of Republic of China under grant NSC 92-2214-E126-001.

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