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Modeling vapor–liquid equilibria for the 1- pentanol + hydrocarbon system using the CPA and PC-SAFT equations of state

Saadia Ghellai


Background: The aim of this work,  on one hand, is to characterize the vapor-liquid equilibria of binary mixtures of 1-pentanol (1) with hydrocarbons (2) using  thermodynamic models such as equations of state and on the other hand to test the capability of these models to represent the isothermal or isobaric phase diagrams (P, x, y ) or (T, x, y) over a wide range of composition .

1-pentanol is considered as one of the most important compound of the second generation of biofuels derived from biomass and wich has a lot of advantages while fuels are repesented by hydrocarbons. The major application of this kind of mixtures is the prediction of the phase behavior of alcohol-gasoline blends, to better understand and model the new formulated gasolines.

Material and Methods:

Different binary systems were selected in this work. A total of nine binary mixtures comprising 1-pentanol and hydrocarbons (n-hexane, n-heptane, n- nonane, cyclohexane,1-hexene, benzene, toluene ). Two equations of state Cubic Plus Association (CPA) and Perturbed-Chain for Statistical Associating Fluid Theory (PC-SAFT) were used to predict or correlate the vapor–liquid equilibria of these mixtures. Two association sites were considered for 1-pentanol, while hydrocarbon was treated as an “inert” compound. For all calculations of the VLE, binary interaction parameter kij was used and an attention is focussed on the values of this one.

Experimental data of VLE for the investigated binary mixtures is collected from literature and is used for the evaluation of two models and the adjustement of the binary interaction parameters kij.

Results: The studied Systems show non-ideal phase behavior and in some cases, azeotropic behavior can be obtained.

Based on the calculated results, it can be established that the two selected equations are able to describe the VLE of 1-pentanol/hydrocarbons type mixtures accurately with a small binary interaction parameter.

Conclusion : Correlation or prediction show good agreement with experimental data for almost investigated systems thus Cubic Plus Association (CPA) and Perturbed-Chain for Statistical Associating Fluid Theory (PC-SAFT) can be used as thermodynamic models to represent this kinds of mixtures.


Modeling, VLE, 1-pentanol, hydrocarbons, equation of state, CPA, PC-SAFT.

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