Thermodynamics of fuels with a biosynthetic component (III): Vapor–liquid equilibrium data for the ternary mixture ethyl 1,1-dimethylethyl ether, n-heptane and 1-hexene at T = 313.15 K

doi:10.1016/j.fluid.2007.12.005

Fluid Phase Equilibria

Volume 265, Issues 1–2, 25 March 2008, Pages 12-16

https://doi.org/10.1016/j.fluid.2007.12.005 Get rights and content

Abstract

Accurate vapor–liquid equilibria were measured for the ternary system ethyl 1,1-dimethylethyl ether + n-heptane + 1-hexene using an isothermal total pressure cell. The experimental data were well correlated using Wohl expansion and Wilson, NRTL and UNIQUAC models. The system shows a slight positive deviation from the ideality. A comparison with similar ternary systems containing other ethers is also discussed in the paper.

Introduction

Ethyl 1,1-dimethylethyl ether (better known as ethyl tert-butyl ether or ETBE) is being used as blending agent in the formulation of gasolines for enhancing the octane number. ETBE can be produced from bioethanol and the use of ETBE in biofuels will contribute to a sustainable society. The knowledge of accurate thermodynamic properties of ETBE containing mixtures is important to improve the thermodynamic models used in the design, simulation and production processes.

This work is part of a research project to obtain new high quality experimental thermodynamic data to develop a model which is able to predict the properties of a synthetic gasoline with a considerable number of components as function of temperature and pressure. Some first results have been already published [1], [2], [3].

In this paper, isothermal vapor–liquid equilibria data for the ternary system (ethyl 1,1-dimethylethyl ether + n-heptane + 1-hexene) at T = 313.15 K are reported.

Section snippets

Materials and experimental method

Ethyl 1,1-dimethylethyl ether was supplied by La Coruña Refinery of REPSOL-YPF, it was purified by rectification at atmospheric pressure. The intermediate fraction was collected and rectified again to a purity >0.997 as determined by gas chromatography (GC).

The hydrocarbons were purchased from Fluka Chemie AG and were of the highest purity available, chromatography quality reagents with a purity >0.98 (GC) for 1-hexene and >0.995 (GC) for n-heptane.

These components were degassed under vacuum

Results

Data reduction was done by Barker's method according to well-established procedures [8], [9] and the pressure deviations are minimized. The non-ideality of the vapor phase was taken into account using the virial equation of state, truncated after the second term. The second virial coefficients are calculated by the Hayden–O’Connell method [10] using the coefficients given by Dymond and Smith [11], these values are given in Table 1.

The Wilson [12], NRTL [13] and UNIQUAC [14] models have been

Discussion

In the literature only isobaric VLE data for (ethyl 1,1-dimethylethyl ether + n-heptane + 1-hexene) at 94 kPa are available [17]. So it is not possible to compare our data with literature data at the same conditions.

The system is quite good correlated using all the models. The root mean square deviation between experimental and calculated pressure is between 21 and 25 Pa with a maximum deviation between 47 and 52 Pa, the highest values are obtained by the Wohl expansion.

The mixtures exhibit a slight

Acknowledgements

Support for this work came from the Spanish Ministry of Education project ENE2006-13349 and from Junta de Castilla y León project VA048/A05.

List of symbols

A_ij, A_ji

adjustable parameters of the correlation models

B_ij, B_ji, B_ii

second virial coefficients

C₀, C₁, C₂

parameters in Eq. (1)

value of G^E/RT

G^E

molar excess Gibbs energy

i,j

constituent identification: 1, 2 or 3

lit

literature value

max

maximum value of the indicated quantity

total pressure

p_{i}^{s}

vapor pressure of pure constituent i

universal gas constant

rmsd

root mean

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Second virial coefficients (Bii, Bij) were calculated by Hayden and O'Connell method [16] using the parameters given by Dymond and Smith [17]. Average values of the experimental vapor pressures (Pis) of pure compounds, molar volumes of pure liquids (ViL) and second virial coefficients (Bii, Bij) are given in Table 2, where vapor pressures are compared with the literature values [18–29]. In Table 3, the experimental values of total pressure, liquid phase composition and vapor phase composition, calculated by Margules equation, are shown for all the binary systems at T = 313.15 K. Also, the sets of data are represented in Fig. 3.
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Accurate experimental data of vapor–liquid equilibria (VLE) are reported for the ternary system (1-pentanol + 2,2,4-trimethylpentane + heptane) and the binary system (2,2,4-trimethylpentane + heptane) at T = 313.15 K.
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Citation Excerpt :
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 of the Antoine equation and the overall mean relative deviation in pressure. For pure 1-hexene, our vapor pressure data agree to within 0.7% with those reported in the literature [7,12–24] in the temperature range (289 to 324) K. As shown in figure 1, for pure MBE our vapor pressure data agree to within ∼3% with those reported in the literature [20,25–28] in the temperature range (263 to 333) K. For MTBE, our vapor pressure data are in good agreement to within 0.9% with those reported in the literature [7,17–19,26–46] in the temperature range (263 to 333) K.
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, H^E, for the two binary systems have been measured at 303.15 K using an isothermal flow calorimeter.

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Thermodynamics of fuels with a biosynthetic component (III): Vapor–liquid equilibrium data for the ternary mixture ethyl 1,1-dimethylethyl ether, n-heptane and 1-hexene at T = 313.15 K

Abstract

Introduction

Section snippets

Materials and experimental method

Results

Discussion

Acknowledgements

List of symbols

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

J. Chem. Eng. Data

J. Chem. Eng. Data (je-2007-005488)

Ind. Eng. Chem. Fundam.

Ind. Eng. Chem. Fundam.

J. Chem. Eng. Data