Closed‐Loops of liquid‐liquid immiscibility in binary mixtures of equal sized molecules predicted with a simple theoretical equation of state

Yelash, Leonid; Kraska, Thomas

doi:10.1002/bbpc.19981020212

Cited by 40 publications

(7 citation statements)

References 30 publications

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“…It has been well documented that the traditional vdW EOS does not predict closed loops and the RK model has a drastically limited capability for predicting such a feature. Also, the Carnahan−Starling−van der Waals model predicts closed loops, , although by means of a mechanism that is completely different from the one discussed in this work …”

Section: Effect Of the Temperature Functionality On The Global Behavi...mentioning

confidence: 60%

Unnoticed Pitfalls of Soave-Type Alpha Functions in Cubic Equations of State

Segura

Kraska

Mejı́a

et al. 2003

Ind. Eng. Chem. Res.

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Empirical thermal cohesion functions, R(T r ), are frequently used in conventional equations of state (EOS) for fitting the vapor pressures of pure fluids. Accurate vapor pressure predictions are required for correlating and/or predicting the phase equilibrium and interfacial tension of multicomponent mixtures. This is the case for the Redlich-Kwong-Soave and Peng-Robinson models, two well-established models for engineering applications. In this work, we demonstrate that, in the case of pure fluids, the R(T r ) function can potentially predict multiple mechanically stable critical points, thus affecting the global topology of phase equilibrium predictions. A detailed analysis, based on the consistency of the prediction of the Joule-Thomson inversion curve, reveals that these predictions are not reliable from a physical point of view. In fact, conventional cubic EOS are able to predict multiple Joule-Thomson inversion curves, a behavior symptomatic of the prediction of multiple stable critical points for pure fluids. Similar pitfalls have been detected in theoretically based EOS such as SAFT and the model proposed by Johnson et al.

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Section: Effect Of the Temperature Functionality On The Global Behavi...mentioning

confidence: 60%

Unnoticed Pitfalls of Soave-Type Alpha Functions in Cubic Equations of State

Segura

Kraska

Mejı́a

et al. 2003

Ind. Eng. Chem. Res.

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show abstract

“…by the SPHCT equation of state Van Pelt et al, 1991 . More recently, the existence of Type VI behavior has been pre-Ž . dicted using the CSvdW Yelash andKraska, 1998 andŽ . Guggenheim Wang et al, 2000 equations of state.…”

Section: Comparison With Experimentsmentioning

confidence: 99%

Equations of state for the calculation of fluid‐phase equilibria

2000

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Progress in de®eloping equations of state for the calculation of fluid-phase equilibria is re®iewed. There are many alternati®e equations of state capable of calculating the phase equilibria of a di®erse range of fluids. A wide range of equations of state from cubic equations for simple molecules to theoretically-based equations for molecular chains is considered. An o®er®iew is also gi®en of work on mixing rules that are used to apply equations of state to mixtures. Historically, the de®elopment of equations of state has been largely empirical. Howe®er, equations of state are being formulated increasingly with the benefit of greater theoretical insights. It is now quite common to use molecular simulation data to test the theoretical basis of equations of state. Many of these theoretically-based equations are capable of pro®iding reliable calculations, particularly for large molecules.

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“…They have also demonstrated that van der Waals' (vdW) equation of state (EOS), which can be derived from the statistical mechanics, is capable of qualitative description of these types of binary phase behavior. Previous studies have established that EOSs with the improved approximation of the hard sphere model may also predict phenomena related to a phase diagram of the sixth type. − These results clearly demonstrate the advantage of theoretically based EOSs over those entirely empirical.…”

Section: Introductionmentioning

confidence: 59%

“…Previous studies have established that EOSs with the improved approximation of the hard sphere model may also predict phenomena related to a phase diagram of the sixth type. [4][5][6][7] These results clearly demonstrate the advantage of theoretically based EOSs over those entirely empirical. Indeed, equations that do not include empirical functionalities can be consistent in the entire thermodynamic phase space.…”

Section: Introductionmentioning

confidence: 61%

About the Relation between the Empirical and the Theoretically Based Parts of van der Waals-like Equations of State

Polishuk

Wisniak

Segura

et al. 2002

Ind. Eng. Chem. Res.

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It is demonstrated that empirical temperature functionalities for the cohesive parameter in van der Waals-like equations can be responsible for prediction of nonphysical results such as fictitious critical points of pure compounds, that can result in prediction of unrealistic phase behavior in the entire thermodynamic phase space. Simple numerical tests for detecting this pitfall are proposed, and the roles played by the empirical and the theoretically based parts in semiempirical engineering equations are investigated. In particular, it is demonstrated that improvement of the accuracy with which equations of state approximate the hard sphere virial coefficients makes the theoretical part more self-sufficient for an accurate description of data. This significantly reduces the contribution of the corresponding empirical part and has a positive effect on the overall robustness and reliability of the model. In addition, an improved theoretical base contributes to the ability of the model so simultaneously and accurately predict both liquid and vapor densities.

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Closed‐Loops of liquid‐liquid immiscibility in binary mixtures of equal sized molecules predicted with a simple theoretical equation of state

Cited by 40 publications

References 30 publications

Unnoticed Pitfalls of Soave-Type Alpha Functions in Cubic Equations of State

Unnoticed Pitfalls of Soave-Type Alpha Functions in Cubic Equations of State

Equations of state for the calculation of fluid‐phase equilibria

About the Relation between the Empirical and the Theoretically Based Parts of van der Waals-like Equations of State

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