Isothermal (vapor + liquid) equilibria and excess enthalpy data of {1-hexene + methyl butyl ether (MBE)} and {1-hexene + methyl tert-butyl ether (MTBE)} binary systems at several temperatures

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Abstract

The vapor pressures of {1-hexene + methyl butyl ether (MBE)} and {1-hexene + methyl tert-butyl ether (MTBE)} binary mixtures and of the three pure components were measured by means of a static device at temperatures between (263 and 333) K. The data were correlated with the Antoine equation. From these data, excess Gibbs functions were calculated for several constant temperatures and fitted to a third-order Redlich–Kister equation using the Barker’s method. Additionally, molar excess enthalpies, HE, for the two binary systems have been measured at 303.15 K using an isothermal flow calorimeter.

Highlights

Vapor pressures of (1-hexene + methyl butyl ether) or (1-hexene + methyl tert-butyl ether) are reported between (263 and 363) K. ► The two mixtures exhibit positive GE. ► Additionally, molar excess enthalpies, HE, for the two binary systems have been measured at 303.15.

Introduction

Formulation of new gasolines, according to the environmental restrictions, means the use of ethers and alcohols as blending agents for enhancing the octane number and a modification of the refinery planning. Simulation of the processes is the first step in the design or optimization of any stage of the plant. The accuracy of a process simulation depends strongly on the thermodynamic models used to describe the physical behavior of the involved components. Very accurate (vapor + liquid) equilibrium (VLE) data are needed to improve the interaction parameters of the predictive models that are used in process simulation packages.

The present paper is part of a research program on VLE and excess enthalpies (HE) in mixtures containing oxygenated polar compounds and different types of hydrocarbons (paraffins, cycloparaffins, aromatics, and olefins) in order to better understand and model these reformulated gasolines. VLE data for binary mixtures containing (1-hexene + tetrahydrofuran) and (1-hexene + tetrahydropyran) have been reported previously [1].

The purpose of the present work is to investigate VLE and HE of {1-hexene + methyl butyl (MBE)} or {1-hexene + methyl tert-butyl ether (MTBE)} binary mixtures with a view to use the results to determine interaction parameters for predictive group contribution methods.

A survey of the literature [2], [3], [4], [5], [6] shows that, for the (1-hexene + MBE) binary mixture, no VLE data are available where, for the (1-hexene + MTBE) binary mixture, there is one data set reported at 313.15 K [7], [17] in the open literature. For HE, there is only one data set available for the (1-hexene + MTBE) binary mixture at 298.15 K [8].

Section snippets

Experimental section

The substances were supplied by Across Organics (Geel, Belgium), Riedel-de-Haen (Hannover, Germany), and Fluka (Buchs, Switzerland). Except for MBE, the two other compounds were fractionally distilled. The purities, tested by GLC, were as follows: 1-hexene (Across, >99%), MBE (Riedel-de-Haen, >99%), and MTBE (Fluka, >99%).

The experimental vapor pressure, P, data were obtained with an apparatus described in detail by Blondel-Telouk et al. [9], [10] as a function of the temperature, T, for

Results and discussion

The experimental vapor pressure data were fitted to the Antoine equation:log10P(mm Hg)=A-BC+t(°C).The objective function Q was the sum of the squared relative deviations in pressure:Q=Pcalc-PexpPexp2.The overall mean relative deviation in pressure is:δPP%=100NPcalc-PexpPexp,where N is the total number of experimental values.

Table 1 lists the experimental vapor pressures of pure 1-hexene, MBE, and MTBE where table 2 lists, for the pure components, the temperature range, the coefficients A, B, C

Summary

VLE data for the two binary mixtures of (1-hexene + MBE), or (1-hexene + MTBE) were measured at several temperatures using a static device. Deviations from Raoult’s law are positive and relatively small. Additionally, excess enthalpy HE was measured for the same binary mixtures at T = 303.15 K.

Acknowledgements

One of the authors (R.H.) gratefully acknowledges a grant from the Algerian Ministry of High Education and Scientific Research (MESRS).

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