Elsevier

Fluid Phase Equilibria

Volume 373, 15 July 2014, Pages 1-19
Fluid Phase Equilibria

Volumetric and viscometric behavior of the binary systems ethyl lactate + 1,2-propanediol, +1,3-propanediol, +tetrahydrofuran and +tetraethylene glycol dimethyl ether. New UNIFAC–VISCO and ASOG–VISCO parameters determination

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Abstract

Densities, refractive indices and viscosities of four binary systems consisting of ethyl lactate with 1,2-propanediol or 1,3-propanediol or tetrahydrofuran (THF) or tetraethylene glycol dimethyl ether (TEGDME) were measured at eight temperatures (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K and atmospheric pressure. From these data, excess molar volumes, deviations in refractive indices and viscosity deviations were calculated and fitted to the Redlich–Kister equation. The obtained results have been analyzed in terms of specific molecular interactions between mixture components and the influence of temperature on them. The modeling of VE binary data was performed with the Peng–Robinson–Stryjek–Vera cubic equation of state (PRSV CEOS) coupled with the van der Waals (vdW1) and CEOS/GE mixing rule introduced by Twu, Coon, Bluck and Tilton (TCBT). The refractive indices of binary mixtures were predicted by various mixing rules and compared with experimental data. The viscosity modeling was done by two types of models: predictive UNIFAC–VISCO and ASOG–VISCO and correlative Eyring–UNIQUAC, Eyring–NRTL, Teja–Rice, Grunberg–Nissan and McAlister equations. In addition, due to the high importance of models for viscosity prediction, the experimental data were used to determine the interaction parameters of several functional groups for their application in the UNIFAC–VISCO and ASOG–VISCO models.

Introduction

The knowledge of physical properties of pure substances and mixtures of commonly used fluids is very important for design and operation of industrial processes. In addition, excess thermodynamic properties, especially excess molar volume can provide valuable information on molecular interactions present in the mixture and lead to better understanding of possibilities for commercial application of the investigated systems.

Ethyl lactate, the most common lactic acid ester, is biodegradable and has excellent solvent properties since it has the ability to dissolve a wide range of chemicals. It finds the use as powerful solvent for varnishes, paints, nitro and ethyl cellulose, gums, oils, dyes, etc., but it is also used in pharmaceutical preparations, food additives and fragrances [1], [2].

The diols, 1,2-propanediol and 1,3-propanediol, are both environmentally friendly, biodegradable and of very low human toxicity [3], [4]. 1,2-Propanediol is generally recognized as safe by the U.S. Food and Drug Administration, approved as food additive and used as a humectant (E1520) [5], but is also used as solvent in the pharmaceutical and cosmetic industry [3]. 1,3-Propanediol has found commercial application in chemical industry, mainly in the production of polymers, composites, adhesives, laminates and coatings [6].

Tetrahydrofuran (THF) is one of the most polar ethers and its main application is as useful industrial aprotic solvent for PVC adhesives and varnishes [7]. It can dissolve a wide range of nonpolar and polar chemical compounds.

Tetraethylene glycol dimethyl ether (TEGDME, tetraglyme) is a polar aprotic solvent with excellent chemical and thermal stability which in combination with high boiling point of 548 K makes it an ideal candidate for separation processes and high temperature reactions [8].

In this paper, densities, refractive indices and viscosities are reported for binary mixtures containing ethyl lactate and diols (1,2-propanediol and 1,3-propanediol) or ethers (THF and TEGDME) at eight temperatures (T = 288.15 K, 293.15 K, 298.15 K, 303.15 K, 308.15 K, 313.15 K, 318.15 K and 323.15 K) and atmospheric pressure. Experimental data were used to calculate excess molar volumes (VE), deviations in refractive index ΔnD and deviations in viscosity Δη correlated afterwards with the Redlich–Kister equation [9].

To the best of our knowledge, volumetric properties, refractive indices and viscosities of selected binary systems have not been previously reported.

Modelling of volumetric properties, refractive index and viscosity of investigated binary systems was also performed. The VE binary data were correlated with the Peng–Robinson–Stryjek–Vera cubic equation of state (PRSV CEOS) [10] coupled with the van der Waals (vdW1) [11] mixing rule and CEOS/GE mixing rule introduced by Twu et al. (TCBT) [12]. The refractive indices were calculated by different equations (Lorentz–Lorenz, Dale–Gladstone, Eykman, Arago–Biot, Newton, and Oster [13]). The predictive UNIFAC–VISCO [14], [15] and ASOG–VISCO [16] models were used for modelling the viscosity with new interaction parameters established on our experimental data. The other models used to calculate viscosity data are correlative Eyring–UNIQUAC [17], Eyring–NRTL [18], Teja–Rice [19], [20], Grunberg–Nissan [21] and McAlister models [22].

Section snippets

Chemicals

For the investigation of thermophysical properties the following chemicals were used: ethyl lactate (98.0 mass%), 1,2-propanediol (99%) and 1,3-propanediol (98%) supplied by Merck, THF (99%) supplied by Sigma Aldrich and TEGDME (99.0 mass%) supplied by Acros Organics (Table 1). Chemicals were kept in dark bottles in an inert atmosphere, used without further purification and degassed just before a sample preparation. In Table 2 densities, dynamic viscosities and refractive indices of pure

Results and discussion

The experimental data of density, refractive index, viscosity, as well as the calculated values of excess molar volume, deviation in refractive index and viscosity deviation, for four binary systems (ethyl lactate + 1,2-propanediol/or +1,3-propanediol/or +THF/or +TEGDME) at eight temperatures T = (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, 318.15 and 323.15) K and at atmospheric pressure are reported in Table 3.

The excess molar volumes VE were calculated from the density data using the

Conclusion

Experimental data on density (ρ), refractive index (nD) and viscosity (η), as well as the excess molar volumes (VE), deviations in refractive indices (ΔnD) and viscosity deviations (Δη), calculated from these data for binary mixtures consisting of ethyl lactate and 1,2-propanediol, or 1,3-propanediol, or THF, or TEGDME, in temperature interval from 288.15 K to 323.15 K and at atmospheric pressure, are presented in this paper. Redlich–Kister equation was used for correlation of excess

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