Examination of the Excess Thermodynamic Properties of <i>n</i>-Alkane Binary Mixtures:  A Molecular Approach

Ramos, dos; Blas, Felipe J.

doi:10.1021/jp0507142

Cited by 17 publications

(23 citation statements)

References 97 publications

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“…1 , and V c 2 are, respectively, the critical temperatures and critical volumes of the pure fluids) it can be observed that the temperature at which H E (x ) 0.5) becomes negative falls within 0.57 and 0.59 for all systems (Figure 1b). Following our suggestions, 9, 10 Blas and dos Ramos 11 were able to reproduce this universal behavior using the soft-SAFT equation. The reduced temperature at which H E (x ) 0.5) becomes negative was predicted by theory as 0.51-0.52.…”

Section: Introductionmentioning

confidence: 69%

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

et al. 2010

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The solubility of xenon in liquid n-pentane and n-hexane has been studied experimentally, theoretically, and by computer simulation. Measurements of the solubility are reported for xenon + n-pentane as a function of temperature from 254 to 305 K. The uncertainty in the experimental data is less than 0.15%. The thermodynamic functions of solvation such as the standard Gibbs energy, enthalpy, and entropy of solvation have been calculated from Henry's law coefficients for xenon + n-pentane solutions and also for xenon + n-hexane, which were reported in previous work. The results provide a further example of the similarity between the xenon + n-alkane interaction and the n-alkane + n-alkane interactions. Using the SAFT-VR approach we were able to quantitatively predict the experimental solubility for xenon in n-pentane and semiquantitatively that of xenon in n-hexane using simple Lorentz-Berthelot combining rules to describe the unlikely interaction. Henry's constants at infinite dilution for xenon + n-pentane and xenon + n-hexane were also calculated by Monte Carlo simulation using a united atom force field to describe the n-alkane and the Widom test particle insertion method.

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Section: Introductionmentioning

confidence: 69%

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

et al. 2010

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“…It is also worth noting that an extrapolation of the high temperature regime of the H m E curves for both systems may lead to small and positive values of H m E at the lowest temperatures, which are much closer to the experimental estimations. Vega 34 and Blas 22,35 have shown that for mixtures of n-alkanes, the experimentally observed positive values of H m E at low temperatures were due to conformational changes in the molecules when they are mixed. Although conformational changes are included in the TraPPE model used in the present simulations, it is nevertheless a united atom model.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, if the same data are plotted against the reduced temperature of the mixtures, it is found that the temperature at which H m E (x = 0.5) becomes negative is practically the same for all systems, falling within 0.57À0.59. 21 Blas and dos Ramos 22 were able to theoretically reproduce this universal behavior using the soft-SAFT equation and suggested that the same trends should exist for other excess properties (e.g., excess molar volume, V m E ) and compositions. Checking the existence of that universal behavior for mixtures of xenon with the lightest n-alkanes is the main goal of this work and an interesting fundamental challenge.…”

Section: Introductionmentioning

confidence: 87%

Excess Thermodynamic Properties of Mixtures Involving Xenon and Light Alkanes: A Study of Their Temperature Dependence by Computer Simulation

et al. 2011

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As a natural extension of a previous work, excess molar enthalpies and excess molar volumes as a function of composition in a wide range of temperatures have been obtained for binary mixtures of xenon with ethane, propane, and n-butane by Monte Carlo computer simulation. Xenon was modeled by a simple spherical Lennard-Jones potential, and the TraPPE-UA force field was used to describe the n-alkanes. One of the main goals of this study is to investigate the temperature dependence of the excess properties for mixtures of xenon and n-alkanes and, if possible, to supplement the lack of experimental data. For all three systems, the simulation results predicted excess volumes in good agreement with the experimental data. As for the excess enthalpies, in the case of (xenon + ethane), the simulation results confirm the negative experimental result and the weak temperature dependence. In the case of (xenon + propane) and (xenon + n-butane), however, the simulation predicts negative excess enthalpies, but those estimated from experimental data are positive. Both excess volumes and enthalpies display a complex dependence on temperature that in some aspects resembles that found for mixtures of n-alkanes.The structure of the liquid mixtures was also investigated by calculating radial distribution functions [g αβ(r)] between each pair of interaction groups for all the binary systems at all temperatures. It is found that the mean distance between xenon and CH2 groups is systematically higher than the distance between xenon and CH3. In addition, the number of groups around xenon in the first coordination sphere was calculated and seems to be proportionally more populated by methyl groups than by methylene groups. The results seem to reflect a preferential and stronger interaction between xenon and CH3, in agreement with previous findings.

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“…Properties such as the excess volume 145 at a pressure of p = 0.10132 MPa. The continuous curves represent the predictions with SAFT-γ Mie group contribution approach, and the dashed curves the corresponding description with SAFT-γ SW. 66,67 and enthalpy have been the subject of numerous studies, 115 including among others the seminal work of Flory and coworkers [138][139][140] and more recently the work of Blas and coworkers [141][142][143] within the SAFT framework. An example of the performance of the SAFT-γ Mie approach is illustrated in Figure 15, where the predictions of the theory are compared to experimental data for the excess speed of sound (u E ) of selected n-hexane + n-alkane binary mixtures 144 (cf.…”

Section: Binary Systemsmentioning

confidence: 99%

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments

Papaioannou

Lafitte

Avendaño

et al. 2014

The Journal of Chemical Physics

248

429

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A group contribution method for associating chain molecules based on the statistical associating fluid theory (SAFT-) The Journal of Chemical Physics 127, 234903 (2007) (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH 3 , CH 2 , and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of compounds not included in the development of group parameters are demonstrated. The performance of the theory is also critically assessed with predictions of the fluid-phase behavior (vapor-liquid and liquid-liquid equilibria) and excess thermodynamic properties of a variety of binary mixtures, including polymer solutions, where very good agreement with the experimental data is seen, without the need for adjustable mixture parameters.

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Examination of the Excess Thermodynamic Properties of n-Alkane Binary Mixtures: A Molecular Approach

Cited by 17 publications

References 97 publications

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

On the Behavior of Solutions of Xenon in Liquid n-Alkanes: Solubility of Xenon in n-Pentane and n-Hexane

Excess Thermodynamic Properties of Mixtures Involving Xenon and Light Alkanes: A Study of Their Temperature Dependence by Computer Simulation

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments

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