Experimental (vapour + liquid) equilibrium data and modelling for binary mixtures of decafluorobutane with propane and 1-butene

doi:10.1016/j.jct.2013.07.020

The Journal of Chemical Thermodynamics

Volume 67, December 2013, Pages 134-142

https://doi.org/10.1016/j.jct.2013.07.020 Get rights and content

Highlights

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Isothermal VLE data for propane + decafluorobutane at (312.92. 327.94 and 342.94) K.
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Isothermal VLE data for 1-butene + decafluorobutane at (312.92, 327.93, and 342.93) K.
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Experimental data correlated with the Peng–Robinson EoS with Wong–Sandler mixing rule.
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Maximum pressure azeotropy observed for both systems.

Abstract

(Vapour + liquid) equilibrium (P–x–y) data are reported at three isotherms for the (propane + decafluorobutane), and (1-butene + decafluorobutane) binary systems. The range of temperatures extended from 312.92 K to 342.94 K. An apparatus based on the “static-analytic” method, which had two electromagnetic ROLSI^TM samplers, for repeatable and reliable equilibrium phase sampling and handling, was used to undertake the measurements. The experimental values were correlated with the “PR–MC–NRTL–WS” model which comprised the Mathias–Copeman alpha function, Wong–Sandler mixing rule, and NRTL local composition model which were incorporated into the Peng–Robinson equation of state. Maximum pressure azeotropy is observed for both systems at all investigated temperatures. Liquid–liquid immiscibility was not observed over the range of temperatures studied.

Introduction

This study forms part of a large research programme, currently being undertaken in the Thermodynamics Research Unit at the University of KwaZulu-Natal, on the thermodynamic properties of fluorocarbons and their mixtures. One of the main objectives of the programme is the development of an extensive experimental property database which would enable the investigation of novel fluorocarbon technologies. Some of the previous studies undertaken have reported pure component saturated vapour pressures and densities for a perfluoroolefin and a perfluoroepoxide [1], [2], and (vapour + liquid) equilibria for binary mixtures involving perfluoroalkanes or perfluoroolefins [3], [4], [5], [6]. The current study involves (vapour + liquid) equilibrium measurements for (perfluorocarbon + hydrocarbon) systems, with this manuscript presenting equilibrium data for binary mixtures involving a hydrocarbon and a perfluoroalkane, viz. (propane + decafluorobutane), and (1-butene + decafluorobutane).

The anomalous behaviour of fluorocarbon solutions has attracted significant research interest [7], [8], [9], [10], [11], [12], [13], [14]. Perfluoroalkane and hydrocarbon mixtures are known to exhibit atypical behaviour for mixtures of non-polar fluids with substantial deviations from ideality and extensive regions of liquid–liquid immiscibility [7], [8], [15]. Such counter-intuitive behaviour has led to numerous and varied applications of fluorocarbon solutions, such as surfactants, elastomers, polymers, water resistant textiles, pesticides, pharmaceuticals, and blood substitutes [14]. In the context of refrigerants, low molar mass fluorocarbons such as R-14 are used for low temperature cascade systems [16], or as constituents in specialty refrigerant mixtures such as R-507 (R-152a/R-218) [17], R-508 (R-23/R-116) [18], and R-509 (R-22/R-218) [19]. Perfluorocarbons are also well known for their high ability to dissolve gases [14]. In this context, fluorocarbons can be investigated as potential enhancing agents in separation processes, in particular for the absorption of common petroleum refinery gases [3].

A convenient tool for the development of chemical and separation technologies is process simulation. Central to most simulations is the calculation of thermodynamic properties at each process condition via a thermodynamic model [20]. Cubic equations of state (EoS) are most commonly used for the design of equilibrium stage separation processes as they provide a good balance between accuracy and simplicity [21]. For any thermodynamic model, the most reliable property estimates are achieved through the fitting of model parameters from reliable experimental “training” data, usually measured at representative process conditions. Considering decafluorobutane, a saturated perfluoroalkane, bibliographic studies indicate a scarcity of phase equilibrium measurements in the open literature. The data of Simons and Mausteller [22] for the (n-butane + decafluorobutane) binary system remains the only reported VLE data outside of the measurements previously reported in this research program [3], [4].

In the present work, novel VLE data for the binary systems (propane + decafluorobutane), and (1-butene + decafluorobutane) are reported over the 312.92 K to 342.94 K temperature range. Saturated vapour pressures for decafluorobutane and propane are also reported over the temperature range of the VLE measurements. The measurements have been conducted on an apparatus based on the “static-analytic” method taking advantage of two electromagnetic ROLSI^TM capillary samplers [23] for reliable equilibrium phase sampling and handling. The experimental data are represented using the “PR–MC–WS–NRTL” model composed of the Mathias–Copeman alpha function [24], Wong–Sandler mixing rule [25], and non-random two-liquid (NRTL) local composition model [26] associated to the cubic Peng–Robinson EoS [27].

Section snippets

Materials

Decafluorobutane (C₄F₁₀, CAS number: 355-25-9) was supplied by Pelchem (South Africa), with a certified purity higher than 0.995 volume fraction. Propane (C₃H₈, CAS number: 74-98-6) was supplied by Messer–Griesheim (France), with a certified purity higher than 0.9995 volume fraction. The 1-butene (C₄H₈, CAS number: 106-98-9) was supplied by Aldrich (Germany), with a certified purity higher than 0.99 volume fraction. Gas chromatographic analysis of each chemical did not reveal any significant

Results and discussion

Experimental saturated vapour pressures of propane and of decafluorobutane are reported in TABLE 2, TABLE 3. The measured vapour pressure data cover the temperature range of the VLE measurements and were used to fit MC parameters for the PR EoS, table 1b. The deviations in pressure for the regression of the alpha function parameters are reported in TABLE 2, TABLE 3. In general, the PR EoS with the implemented MC expression provides a good correlation of the vapour pressure data with absolute

Conclusions

Novel isothermal (P–x–y) VLE data are presented at three temperatures each for the (propane + decafluorobutane), and (1-butene + decafluorobutane) binary systems over the 312.92 K to 342.94 K temperature range. The experimental values were measured on a “static-analytic” type apparatus taking advantage of two electromagnetic ROLSI^TM capillary samplers for repeatable and reliable equilibrium phase sampling and handling. The experimental results are given with the following expanded uncertainties (k =

Acknowledgements

This work is based upon research supported by the South African Research Chairs Initiative of the Department of Science and Technology, and National Research Foundation. Pelchem is acknowledged for the supply of decafluorobutane (R-610).

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Experimental (vapour + liquid) equilibrium data and modelling for binary mixtures of decafluorobutane with propane and 1-butene

Highlights

Abstract

Introduction

Section snippets

Materials

Results and discussion

Conclusions

Acknowledgements

Fluid Phase Equilib.

J. Chem. Thermodyn.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

Int. J. Refrig.

Int. J. Refrig.

Appl. Therm. Eng.

Int. J. Refrig.

Fluid Phase Equilib.

Fluid Phase Equilib.

Fluid Phase Equilib.

Int. J. Refrig.

Int. J. Refrig.

Ind. Eng. Chem. Res.

J. Chem. Eng. Data

J. Chem. Eng. Data

Fluid Phase Equilib.

J. Chem. Eng. Data

J. Chem. Eng. Data