“…Furthermore, the theory of critical phenomena has progressed so that it has become possible to formulate scaled equations of state for the thermodynamic properties of mixtures in a broad region of thermodynamic states around the critical locus [5][6][7][8][9][10][11]. One interesting mixture is that of carbon dioxide and ethane, since this mixture exhibits critical azeotropy [5].…”
This note presents an update of an evaluation of the critical parameters of mixtures of carbon dioxide and ethane, previously reported by Abbaci et al. (Int. J. Thermophys. 13, 1043 (1993)).
“…Furthermore, the theory of critical phenomena has progressed so that it has become possible to formulate scaled equations of state for the thermodynamic properties of mixtures in a broad region of thermodynamic states around the critical locus [5][6][7][8][9][10][11]. One interesting mixture is that of carbon dioxide and ethane, since this mixture exhibits critical azeotropy [5].…”
This note presents an update of an evaluation of the critical parameters of mixtures of carbon dioxide and ethane, previously reported by Abbaci et al. (Int. J. Thermophys. 13, 1043 (1993)).
“…There are few crossover models of mixtures formulated in terms of the chemical potential that incorporate scaling laws in the critical region and transform into an analytical EOS far away from the critical region. Examples include the six-term crossover model developed by Sengers and co-workers, − the crossover Leung−Griffiths model developed by Belyakov et al, , and the more extensive parametric crossover model developed by Kiselev and Rainwater . The Helmholtz free energy in the latter model was represented in a universal parametric form, which does not depend on the details of the intermolecular interaction and is equally valid for any pure fluid and binary mixture in the critical region, including ionic and aqueous solutions.…”
Section: Introductionmentioning
confidence: 99%
“…Therefore, if the critical locus of the mixture is known, all other thermodynamic properties can be predicted. So far, the computer program CREOS97, based on the parametric crossover model developed by Kiselev and Rainwater, has been successfully applied to the prediction of the vapor−liquid equilibrium (VLE) surface and thermodynamic properties for more than 20 binary mixtures. − However, most of these applications were restricted to type I binary mixtures, according to the Van Konynenberg−Scott specification, and the question of the application of the theoretical crossover models to other types of binary mixtures remains open. Few attempts were made to extend the nonclassical crossover approach to the binary mixtures near the liquid−liquid critical points, types V and II binary mixtures.…”
In this paper, we report new PVTx measurements for water + toluene binary mixtures at 11 near-critical and supercritical isotherms T ) 623, 627, 629, 631, 633, 643, 645, 647, 649, 651, and 673 K and pressures up to 39 MPa at a fixed concentration of x ) 0.0287 mole fraction of toluene. Using these PVTx data together with data obtained earlier by other authors, we developed a crossover Helmholtz free-energy model (CREOS) for pure toluene and dilute aqueous toluene solutions in a wide range of the parameters of state around the vapor-liquid critical points. In the temperature range 593 K e T e 680 K and density range 100 kg‚m -3 e F e 500 kg‚m -3 , the CREOS reproduces the PVT data for pure toluene with an average absolute deviation (AAD) of about 0.5%, the C P data with an AAD of about 1%, and the sound velocity data with an AAD of about 2.6%. In water + toluene mixtures, the CREOS yields an adequate description of all available experimental data in the region bounded by 0.35F c (x) e F e 1.65F c (x) and 0.98T c (x) e T e 1.15T c (x) at x e 0.04 mole fraction of toluene. The possibility of extrapolating the CREOS model to lower temperatures, 0.93T c e T eT c , and higher densities and concentrations, up to F ) 2F c and x ) 0.12, is also discussed.
“…Therefore, we were not able to reproduce with the HRX-SAFT EOS experimental data asymptotically close to the critical point. However, it is important to note that, because of the complexity of this mixture, a simultaneous representation of the P − x and P − ρ VLE data have not been achieved even with the field-variable formulated crossover Leung-Griffiths model, and the results presented in Figures −7 look rather impressive. 5 Pressure−composition (a) and pressure−density (b) VLE isotherms for carbon dioxide + methanol mixture.…”
Section: Comparison With Experimental Datamentioning
In this work, we extend the pure fluid crossover statistical associating fluid theory (HRX-SAFT) equation of
state (EOS) (Kiselev et al., Fluid Phase Equilib.
2001, 183−184, 53) to fluid mixtures of polar and associating
components. HRX-SAFT incorporates non-analytic scaling laws in the critical region and is transformed into
the analytical, classical HR-SAFT EOS far away from the critical point. Pure CO2, H2O, and CH3OH are
modeled as associating chain molecules with two association sites (i.e., model 2B). For all three pure substances,
the HRX-SAFT EOS reproduces the vapor pressure data from the triple point to the critical temperature with
an average absolute deviation (AAD) of about 1%, the saturated liquid and vapor densities with an AAD of
about 1−3%, and the single-phase pressures in the one-phase region with an AAD of about 2−3%. Using
classical composition-dependent mixing rules, we have also applied the HRX-SAFT EOS to binary mixtures.
For the non-association terms in the classical HR-SAFT, we used the vdW1 mixing rules with one constant
binary interaction parameter (k
ij
). For the mixture association term, we assumed that there is cross association
between the carbon dioxide oxygens and the hydrogens in methanol and water. The HRX-SAFT mixture
model was tested against extensive experimental data for VLE, PVTx, and excess properties in carbon dioxide
+ water, carbon dioxide + methanol, and water + methanol mixtures.
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