Correlation and Prediction of Water Content in Alkanes Using a Molecular Theory

Emborsky, Christopher P.; Cox, Kenneth R.; Chapman, Walter G.

doi:10.1021/ie200296e

Cited by 24 publications

(27 citation statements)

References 51 publications

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“…Though the LB rule may not be very accurate, the water-alkane interaction energy here is too high (ξ = 1.67) to be attributed to the inadequacy of the LB rule. Values of LJ parameters close to the ones we find here were obtained in the theoretical work of Emborsky et al 29 when they calculated the solubility of water in alkanes using the PC-SAFT model for alkanes. They found that a value of ε W /k = 207 K was required to match the solubility of water in the different alkanes.…”

Section: Resultssupporting

confidence: 88%

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions

Ballal

Venkataraman

Fouad

et al. 2014

The Journal of Chemical Physics

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Intermolecular potential models for water and alkanes describe pure component properties fairly well, but fail to reproduce properties of water-alkane mixtures. Understanding interactions between water and non-polar molecules like alkanes is important not only for the hydrocarbon industry but has implications to biological processes as well. Although non-polar solutes in water have been widely studied, much less work has focused on water in non-polar solvents. In this study we calculate the solubility of water in different alkanes (methane to dodecane) at ambient conditions where the water content in alkanes is very low so that the non-polar water-alkane interactions determine solubility. Only the alkane-rich phase is simulated since the fugacity of water in the water rich phase is calculated from an accurate equation of state. Using the SPC/E model for water and TraPPE model for alkanes along with Lorentz-Berthelot mixing rules for the cross parameters produces a water solubility that is an order of magnitude lower than the experimental value. It is found that an effective water Lennard-Jones energy ε(W)/k = 220 K is required to match the experimental water solubility in TraPPE alkanes. This number is much higher than used in most simulation water models (SPC/E-ε(W)/k = 78.2 K). It is surprising that the interaction energy obtained here is also higher than the water-alkane interaction energy predicted by studies on solubility of alkanes in water. The reason for this high water-alkane interaction energy is not completely understood. Some factors that might contribute to the large interaction energy, such as polarizability of alkanes, octupole moment of methane, and clustering of water at low concentrations in alkanes, are examined. It is found that, though important, these factors do not completely explain the anomalously strong attraction between alkanes and water observed experimentally.

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Section: Resultssupporting

confidence: 88%

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions

Ballal

Venkataraman

Fouad

et al. 2014

The Journal of Chemical Physics

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“…To minimize the number of variables, we first treat water as a single sphere with a chain length m = 1. Second, we employ the results of Emborsky and Chapman(EC) 23 who obtained the reference system energy εww for water in PC-SAFT by regressing to water solubility in alkane data. As water is dilute in the hydrocarbon phase, their value of reference energy (εww = 209.84 kB) will correspond to   As can be seen, both cases give similar errors in the description vapor pressure; however, case II gives a substantial improvement in the overall description of the liquid densities (see Fig.…”

Section: Iii: Resultsmentioning

confidence: 99%

“… was fit to solubility water solubility in HC data. 23 The test is then, how well does the theory take this information and predict the solubility of HC in the water phase? As can be seen, the new approach (case II) is much more successful.…”

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confidence: 99%

On the cooperativity of association and reference energy scales in thermodynamic perturbation theory

Marshall

2016

The Journal of Chemical Physics

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Equations of state for hydrogen bonding fluids are typically described by two energy scales. A short range highly directional hydrogen bonding energy scale as well as a reference energy scale which accounts for dispersion and orientationally averaged multi-pole attractions. These energy scales are always treated independently. In recent years, extensive first principles quantum mechanics calculations on small water clusters have shown that both hydrogen bond and reference energy scales depend on the number of incident hydrogen bonds of the water molecule. In this work, we propose a new methodology to couple the reference energy scale to the degree of hydrogen bonding in the fluid. We demonstrate the utility of the new approach by showing that it gives improved predictions of water-hydrocarbon mutual solubilities.

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“…These authors have demonstrated that accurate modeling of two and three‐phase equilibria in aqueous systems of various hydrocarbons can be achieved by implementing the APACT EoS with zero and close to zero values of binary parameter k 12 . Later on, further progress in improving the predictive character of estimating phase equilibria in alkane‐water mixtures has been achieved by Emborsky et al who have fitted the nonpolar and non‐associating PC‐SAFT EOS 7 parameters for pure water to its solubility data in liquid alkanes at ambient conditions without additional determination of the binary adjustable parameters. This approach has been successfully extrapolated to predict water solubility in n ‐alkanes at the higher temperatures and pressures.…”

Section: Introductionmentioning

confidence: 99%

Predicting phase behavior in aqueous systems without fitting binary parameters II: Gases and non‐aromatic hydrocarbons

2017

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This investigation continues a series of studies evaluating the capability of the recently proposed CP‐PC‐SAFT and sPC‐SAFT of Liang et al. to estimate the thermodynamic properties of aqueous systems in the entirely predictive manner. Similarly to the previously considered systems, CP‐PC‐SAFT remains a realistic estimator of the available data on critical loci, high pressure‐high temperature phase equilibria and volumetric properties also in the cases of non‐polar gases and non‐aromatic hydrocarbons from argon and nitrogen till n‐eicosane and squalene while keeping zero values of binary parameters. Nevertheless, such application of the model poses certain unavoidable compromises on its accuracy. Inter alia, CP‐PC‐SAFT is a particularly inaccurate estimator of the water‐rich liquid phases away from the critical points. sPC‐SAFT predicts these data in a more reliable manner. Moreover, its predictive capability goes beyond the liquid phases and it exhibits a remarkable accuracy in forecasting various phase equilibria below the critical point of water. © 2017 American Institute of Chemical Engineers AIChE J, 2017

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Correlation and Prediction of Water Content in Alkanes Using a Molecular Theory

Cited by 24 publications

References 51 publications

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions

Isolating the non-polar contributions to the intermolecular potential for water-alkane interactions

On the cooperativity of association and reference energy scales in thermodynamic perturbation theory

Predicting phase behavior in aqueous systems without fitting binary parameters II: Gases and non‐aromatic hydrocarbons

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