Perturbed Dipolar Chains: A Thermodynamic Model for Polar Copolymers

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We present a predictive model for the saturated water concentration in n-alkanes based on a theoretical equation of state for the hydrocarbon rich phase and a water equation of state for the aqueous phase. By considering a polar or associating component at low concentration in a nonpolar solvent, we can neglect polar or hydrogen bonding interactions in the hydrocarbon rich phase, thus reducing the number of fitted parameters. The approach allows us to determine the intrinsic pure component equation of state parameters independent of polar and associating interactions. As an example, the nonpolar, non-associating equation of state parameters for water are determined by fitting water solubility data in liquid hydrocarbons (carbon numbers (CN) = 4À13, 16) at ambient conditions. Using the PC-SAFT equation of state, a predictive model for the solubility of water in n-alkanes is produced. Comparisons of the model are presented with binary mixture experimental data for methane to decane across a wide range of conditions. Excellent qualitative and good quantitative agreement is exhibited without fitting a binary interaction parameter. The model is then extrapolated to predict water solubility in n-alkanes as a function of temperature, pressure, and carbon number for conditions where experimental data is of questionable validity or unavailable. Implications on the potential model used in molecular simulations are also discussed.

Section: Theory and Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Emborsky

Cox

Chapman

2011

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“…The model constants a ji and b ji are fit to experimental data of n-alkanes and are reported by Gross and Sadowski. 24 The PC-SAFT equation of state has been applied with great success to a wide variety of systems including associating and nonassociating molecules, 24,47,48 polar systems, 47,49,50 and polymer systems, [50][51][52][53] as well as other complex systems. 54,55 The EOS requires few parameters that scale well within a homologous series, making it a powerful tool for systems where little experimental data is available.…”

Section: Pc-saft Equation Outside the Critical Regionmentioning

confidence: 99%

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

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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.

“…Research led by Jog and Chapman showed that the dipolar contribution to the Helmholtz free energy can be added to the sum as in eq 1 without modifying the hard-sphere, chain, and dispersion terms. , Two approaches for expressing the dipolar contribution ( a polar ) are considered in this study; therefore, the basic assumptions and the fundamental equations for both dipolar terms are presented in this section.…”

Section: Theorymentioning

confidence: 99%

Modeling of Polar Systems with the Perturbed-Chain SAFT Equation of State. Investigation of the Performance of Two Polar Terms

and¹,

Chapman²,

and³

et al. 2005

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107

120

The Perturbed-Chain SAFT (PC-SAFT) equation of state is applied to model phase equilibria and the thermodynamic properties of ethers and esters. A systematic study of these two homologous series is conducted, and the performance of two different approaches for including the dipolar interactions in the equation of state is evaluated. Although both Polar PC-SAFT [dipolar contribution due to Jog and Chapman, Mol. Phys. 1999, 97, 307-319] and PC-SAFT + Fischer [dipolar contribution by Saager and Fischer, Mol. Simul. 1991, 6, 27-49] yield similar results for the considered systems, the parameters of Polar PC-SAFT are more physically meaningful than those of PC-SAFT + Fischer. Consequently, Polar PC-SAFT is considered to be more suitable for extrapolations, and for application to components that have multiple polar groups in the chain.