Elsevier

Fluid Phase Equilibria

Volume 491, 1 July 2019, Pages 35-44
Fluid Phase Equilibria

Density of biofuel mixtures (Dibutyl ether + Heptane) at temperatures from (298.15–393.15) K and at pressures up to 140 MPa: Experimental data and PC-SAFT modeling

https://doi.org/10.1016/j.fluid.2019.02.028Get rights and content

Abstract

Density has been reported to binary mixtures (552 points) of dibutyl ether (DBE) + heptane in the composition range (4 compositions; 0.325 ≤ dibutyl ether mole fraction x ≤ 0.85), between 298.15,393.15 K, and for 23 pressures ranging from 0.1 MPa to 140 MPa.

These experimental measurements were carried out using an apparatus, comprising a vibrating tube densimeter Anton Paar, calibrated with an uncertainty of about 0.7 kg· m-3.

The volumetric behavior and excess molar volume of DBE + heptane were modeled using PC-SAFT equation. The PC-SAFT parameters of DBE and heptane were optimized using experimental density data at atmospheric pressure. The density of the mixture was reasonably well predicted, with a mean relative difference between 0.0009% and 1.99%. Whereas the excess molar volume not satisfactorily predicted.

A Tait equation was used to adjust the experimental density data. In addition, from this equation the isobaric thermal expansion and the isothermal compressibility were derived.

Introduction

Transport is an extremely energy-intensive sector. Dependent on petroleum products, it is also the area where research to produce alternative fuels is intensifying. In fact, transportable energy sources include fossil fuels, biomass and renewable or even nuclear energy (via electricity generation) [1].

This extreme petroleum dependency of the modes of transport poses environmental problems. As the carbon content of petroleum products, greenhouse gas emissions and local pollution associated with refining and combustion activities in engines are major issues. Moreover, these issues are becoming increasingly important in a context in which sustainable development is taking center stage. However, the extreme dependence of the transport sector on oil is more relevant than ever [2].

Reducing greenhouse gas emissions has become an issue of global importance. In this context, the search for less polluting alternative fuels has become both an environmental and an economic requirement [3].

The formulation of a new gasoline, taking into account environmental constraints, carries to use ethers and alcohols as additives to gasoline because of their reducing properties of polluting emissions and their ability to increase the octane rating [4].

Among the promising compounds that can be used as additives with conventional gasolines and as a source of energy, we mention the case of dibutyl ether because of their high-energy power [5].

DBE can be obtained as a value-added additive for second-generation biofuels and has been included in recent international regulations to promote the use of renewable energy sources for transport [6].

The study of the behaviors of liquid hydrocarbon and ether presents today a great interest for the thermodynamics. In fact, the experimental studies on the properties of the binary mixtures became indispensable to provide valuable information on fluid behavior under different temperature and pressure conditions. One of these properties is density and its derivatives. .This work is a continuation of the other previous works by our group on the density of binary dibutyl ether (DBE) mixtures with 1-butanol, 1-propanol, 1-hexanol and 2-propanol at high temperature and high pressure [[7], [8]].

The purpose of this research is to study binary dibutyl ether (DBE) mixtures with heptane and to examine intermolecular interactions during the mixing process. For that, we presented the experimental densities of DBE + heptane at pressures 0.1 MPa up to 140 MPa and between 298.15 K and 393.15 K over the whole the composition range (4 DBE molar ratio composition, x1 = 0.325, 0.500, 0.675, 0.850. However, the densities, the excess molar volumes, the isobaric thermal expansion coefficient and the isothermal compressibility coefficient have been medeled using equation of state (Eos) based on Perturbed-Chain Statistical Associating Fluid Theory (PC SAFT).

Section snippets

Materials

Dibutyl Ether (C8H18O, molar mass 130.228 g mol−1, CAS. 142-96-1) and heptane (C7H16, molar mass 100.201 g mol−1, CAS. 142-82-5) were given from Sigma-Aldrich with mole fraction purity of respectively 0.993 and 0.995. The pure component properties are reported in Table 1. These chemicals component are directly injected, into the high-pressure cell as soon as the bottles were open and were subject to no further purification.

Measurement technique. Experimental procedure

The density is measured as a function of the pressure p (up to 140 MPa)

PC-SAFT

PC-SAFT model was developed by Gross and Sadowski [[16], [17]], by considering the hard chain fluid as the reference system and applying the perturbation theory of Barker and Henderson [[18], [19]].

This model is applied to mixtures of small spherical molecules such as gases, non-spherical solvents and polymers. The initial PC-SAFT model of Gross and Sadowski assumes the limited association and models the interaction between the components with only a dispersion contribution.

PC-SAFT equation is

Density

The densities of binary mixtures of x dibutyl ether + (1-x) heptane (4 DBE molar ratio composition, x1 = 0.325, 0.500, 0.675, 0.850) were measured as a function of the temperature from (298.15–393.15) K and at pressures up to 140 MPa (23 isobars). The results are listed in Table 3. No data were found in the literature for the same binary mixtures at high pressure or high temperature. The density of pure DBE and heptane has been already determined with a comparative study and reported in Ref. [

Conclusion

522 experimental density data for the compressed liquid phase of the binary system DBE + heptane have been measured at 298.15, 313.15, 333.15, 353.15, 373.15 and 393.15 K and at pressures up to 140 MPa (23 isobars), with an absolute uncertainty of 0.7 kg m−3. However, from these density values, derived properties, αp, and κT, and excess molar volumes were calculated. Tait-type equation is used to correlated the experimental density.

Concerning modeling, the PC-SAFT equation was used to correlate

References (28)

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