Excess enthalpies of binary and ternary mixtures containing dibutyl ether (DBE), 1-butanol, and heptane at T = 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 + heptane} 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, 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

The use of oxygenated compounds, such as ethers and alcohols, as gasoline-blending agents has been proposed to reduce emissions of new reformulated gasoline. (Ether + alcohol + alkane) are of interest as model mixtures for gasoline in which the alcohol and the ether act as non-polluting, high octane number blending agents [1]. This work continues a study on excess molar enthalpies of mixtures {dibutyl ether (DBE) + 1-butanol + alkane}. 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 [2]. In a previous paper [3], data for the ternary mixture {DBE + 1-butanol + cyclohexane} at T = 298.15 K have been published. Experimental excess molar enthalpies of the ternary system {DBE + 1-butanol + heptane} and the corresponding binary systems at T = 298.15 K and at T = 313.15 K are reported in this work. Excess molar enthalpies have been measured with a quasi-isothermal flow calorimeter. The experimental data have been fitted using a Redlich–Kister [4] equation, the NRTL [5] and the UNIQUAC [6] models. The values of the standard deviation indicate the agreement between the experimental results and those calculated from the equations.

Section snippets

Experimental section

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%. All reagents were checked by gas chromatography, and the values of purity obtained were >99.6% for DBE, >99.8% for heptane and >99.8% for 1-butanol. The water content for 1-butanol was checked to be less than 0.009%.

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

Results and discussion

The experimental excess molar enthalpies obtained in this work for the binary mixtures (DBE + heptane), (DBE + 1-butanol), and (heptane + 1-butanol) at T = 298.15 K and 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, is given by equation (1), in which the Ai coefficients are determined by the unweighted least-squares methodHE=x·(1-x)·i=1nAi·(2x-1)i-1.Binary systems

Conclusions

Isothermal excess enthalpies at the temperatures of 298.15 K and 313.15 K for the ternary system {DBE (1) + heptane (2) + 1-butanol (3)} and its constituent binary systems were determined by using an isothermal flow calorimeter. All the binary systems show endothermic HE behavior at the measured temperatures. The HE behavior is asymmetric in the binary mixtures containing the alkanol, due to the hydrogen bonding association effect of the alkanol. The two binary systems containing 1-butanol show a

Acknowledgements

This article 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.

References (14)

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