Elsevier

Fluid Phase Equilibria

Volume 284, Issue 2, 25 October 2009, Pages 106-113
Fluid Phase Equilibria

Excess enthalpies of ether + alcohol + hydrocarbon mixtures: Binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol and benzene at 298.15 K and 313.15 K

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Abstract

Experimental excess molar enthalpies of the ternary systems dibutyl ether (DBE) + 1-butanol + benzene and the corresponding binary systems at T = 298.15 K and T = 313.15 K at atmospheric pressure are reported. A quasi-isothermal flow calorimeter has been used to make the measurements. All the binary and the ternary systems show endothermic character. The experimental data for the binary and ternary systems have been fitted using the Redlich-Kister equation and the NRTL and UNIQUAC models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.

Introduction

Ether + alcohol + hydrocarbon mixtures are of interest as model mixtures for gasoline in which the alcohol and the ether act as non-polluting, high octane number blending agents. This work continues a study on excess molar enthalpies of dibutyl ether (DBE) + alcohol + hydrocarbon mixtures. In a previous paper [1], data for the ternary mixture DBE + 1-butanol + cyclohexane at T = 298.15 K have been published. DBE is used as blending agent in reformulated gasoline and 1-butanol is a basic component in the synthesis of the ether, and therefore is always contained as an impurity. Though benzene is reduced to a minimum in present fuel regulations, it is of interest because it is a representative of aromatic compounds in group contribution models for fuel mixtures. Experimental excess molar enthalpies of the ternary system DBE + 1-butanol + benzene and the corresponding binary systems at T = 298.15 K and at T = 313.15 K at atmospheric pressure are reported in this work. Excess molar enthalpies have been measured with a quasi-isothermal flow calorimeter. The experimental data have been fitted using polynomial equations and group contribution models. The values of the standard deviation indicate good agreement between the experimental results and those calculated from the equations.

Section snippets

Experimental

All the chemicals used here were purchased from Fluka Chemie AG and were of the highest purity available, chromatography quality reagents (of the series puriss p.a.) with a stated purity >99.5%. The purity of all reagents was checked by gas chromatography, and the values of purity obtained were >99.6% for DBE, >99.9% for benzene and >99.8% for 1-butanol. The water content of 1-butanol was checked to be less than 0.02%.

Excess molar enthalpies have been measured with a quasi-isothermal flow

Results and discussion

The experimental excess molar enthalpies obtained in this work for the binary mixtures DBE + benzene, DBE + 1-butanol and benzene + 1-butanol at T = 298.15 K and T = 313.15 K are listed in Table 1, Table 2.

For binary systems, there are several models and empirical equations proposed to fit the HE measurements. One of them, the Redlich-Kister equation [7], is given by Eq. (1), in which the Ai coefficients are determined by the unweighted least-squares method.HE=x(1x)i=1nAi(2x1)i1

Binary systems have

Conclusions

Isothermal excess molar enthalpies at T = 298.15 K and T = 313.15 K for the ternary system DBE (1) + benzene (2) + 1-butanol (3) and its constituent binary systems were determined by using an isothermal flow calorimeter. All the binary systems show endothermic and strongly asymmetric HE behaviour at the measured temperatures. The two binary systems containing 1-butanol show a decreasing value of HE with increasing temperature, while DBE + benzene shows the opposite behaviour. Intermolecular and association

Acknowledgements

This paper is part of the Doctoral Thesis of F. Aguilar.

Support for this work came from the Dirección General de Investigación (DGI), Ministerio de Educación y Ciencia, Spain, Projects ENE2006-12620 and ENE2006-13349, and from the Consejería de Educación, Junta de Castilla y León, Spain, Project BU021A08.

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