Prediction Methods for the Critical Temperature of n -Alkanes

Amorós, J.

doi:10.1080/0031910021000004856

Cited by 4 publications

(7 citation statements)

References 18 publications

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“…The previously given correlations (eqs –) for ϕ, L , and ξ, coupled with the correlations given by Gross and Sadowski for m , σ, and ε, are tested for select heavy n -alkanes (C 20 , C 24 , C 30 , and C 36 ). Table and Figure elucidate the remarkable ability to predict the critical behavior for the heavy members using these correlations, when compared with simulation data and available experimental data. ,, Figures and show the critical temperature T c , and critical pressure, P c , as a functions of carbon number before and after renormalization corrections.…”

Section: Resultsmentioning

confidence: 92%

“…For low molecular weight n -alkanes (up to C 9 H 20 ) the critical properties are well-known from experiment. However, for heavier n -alkanes, critical property measurements are impeded since the critical temperatures exceed the temperature of the onset of thermal decomposition . Teja and co-workers , and Nikitin et al , represent the few to successfully make critical property measurements for heavier alkanes, but the experimental error of these critical values can be quite large.…”

Section: Resultsmentioning

confidence: 99%

“…However, for heavier n-alkanes, critical property measurements are impeded since the critical temperatures exceed the temperature of the onset of thermal decomposition. 60 Teja and co-workers 61,62 and Nikitin et al 63,64 represent the few to successfully make critical property measurements for heavier alkanes, but the experimental error of these critical values can be quite large. For these reasons, in this work the crossover parameters were fit, using the procedure described above, for C 2 -C 8 and for C 12 and C 16 .…”

Section: Improving Pc-saft + Rgmentioning

confidence: 99%

“…Table 3 and Figure 8 elucidate the remarkable ability to predict the critical behavior for the heavy members using these correlations, when compared with simulation data 65 and available experimental data. 60,61,66 Figures 9 and 10 show the critical temperature T c , and critical pressure, P c , as a functions of carbon number before and after renormalization corrections.…”

Section: Improving Pc-saft + Rgmentioning

confidence: 99%

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Renormalization-Group Corrections to a Perturbed-Chain Statistical Associating Fluid Theory for Pure Fluids Near to and Far from the Critical Region

Bymaster

Emborsky

Dominik

et al. 2008

Ind. Eng. Chem. Res.

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A perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state has been extended to include a crossover correction, based on White's work with renormalization-group (RG) theory, that accounts for the contributions of long-wavelength density fluctuations in the critical region. In the critical region, the improved crossover equation of state provides the correct nonclassical critical exponents. Away from the critical region, the crossover equation reduces to the original PC-SAFT equation, therefore maintaining the accuracy of PC-SAFT in this region. No modifications to the original PC-SAFT molecular parameters are necessary, therefore allowing for an accurate description of thermodynamic properties from the triple point to the critical point. Excellent agreement with vapor-liquid equilibrium experimental data for the n-alkane family is obtained inside and outside the critical region, and all critical constants T c , P c , and F c are calculated within their respective experimental errors. The extrapolative abilities of the RG parameters are demonstrated for higher molecular weight chains. Finally, the present results are contrasted with results from other groups using alternative interpretations of White's theory.

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Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Section: Improving Pc-saft + Rgmentioning

confidence: 99%

Section: Improving Pc-saft + Rgmentioning

confidence: 99%

See 2 more Smart Citations

Renormalization-Group Corrections to a Perturbed-Chain Statistical Associating Fluid Theory for Pure Fluids Near to and Far from the Critical Region

Bymaster

Emborsky

Dominik

et al. 2008

Ind. Eng. Chem. Res.

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show abstract

“…In the long chain limit, P c tends to zero and the prediction of SPEAD11+RG EOS for critical temperature ( T c ∞ ) is around 1300 K, which is in acceptable agreement with available predictions. Amoros reviewed several empirical correlations for critical temperature of n -alkanes and proposed T c ∞ ≈ 1020 K. Nikitin suggested that critical temperature for n -alkanes scales as NC –0.5 with T c ∞ ≈ 1257 K while Pamies and Vega estimated T c ∞ for n -alkanes to be around 1320 K using soft-SAFT EOS.…”

Section: Resultsmentioning

confidence: 99%

Renormalization Group Adaptation to Equations of State From Molecular Simulation

Ghobadi

Elliott

2013

Ind. Eng. Chem. Res.

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We have previously demonstrated how combination of Discontinuous Molecular Dynamics (DMD) and Thermodynamic Perturbation Theory (TPT) can be employed to characterize the entire phase diagram from molecular simulations. Nevertheless, the precision of that characterization in the (nonanalytic) critical region is unavoidably limited by the analytic behavior inherent in TPT. In the present work, we adapt White’s Renormalization Group (RG) methodology to address this deficiency. We applied the DMD/TPT/RG methodology to n-alkanes ranging in molecular weight to 1122 (C80) with emphases on the asymptotic behavior in the long chain limit. Critical properties were estimated in the approach to the long chain limit whereas experimental measurements become sparse at molecular weights above 506 (C36). For example, the critical temperature of polyethylene is estimated at roughly 1300 K and we are able to speculate that the critical compressibility factor is lower than previous estimates of Z c = 0.2. Where experimental data for T c are available, deviations of the RG correlations are roughly 4 K, compared to 20 K for the classical implementation of TPT. Although White’s RG theory has a robust physical background, a number of limitations were noted during its adaptation to DMD/TPT, some of which are inherent in the method and unavoidable. To begin, the methodology is not readily adapted to the transferable site-based perspective implicit in molecular simulation models. Therefore, a procedure for translating from a site-based perspective to a segment-based perspective was developed. Second, it was noted that previous implementations resulted in binodal curves that were excessively “flat” in the critical region as chain length increased. An adaptation was made in the “t” exponent to eliminate anomalous behavior of long chains in the transition from the critical to the liquid regime. Regarding the implicit limitations, we note that White’s method alters the van der Waals loop inside the binodal in a destructive way, it requires at least three adjustable parameters that must be predicted for its implementation when experimental data are not available and it suffers from numerical limitations that hinder its application to compounds with relatively low critical pressure and density such as long chain n-alkanes.

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Phase‐Transition Regularities in Critical Constants, Fusion Temperatures and Enthalpies of Chemically Similar Chainlike Structures

Balaban¹,

Klein²,

March³

et al. 2005

ChemPhysChem

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Prediction Methods for the Critical Temperature of n -Alkanes

Cited by 4 publications

References 18 publications

Renormalization-Group Corrections to a Perturbed-Chain Statistical Associating Fluid Theory for Pure Fluids Near to and Far from the Critical Region

Renormalization-Group Corrections to a Perturbed-Chain Statistical Associating Fluid Theory for Pure Fluids Near to and Far from the Critical Region

Renormalization Group Adaptation to Equations of State From Molecular Simulation

Phase‐Transition Regularities in Critical Constants, Fusion Temperatures and Enthalpies of Chemically Similar Chainlike Structures

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