Polymer-Supercritical Fluid Calculations

When dealing with mixtures it is necessary to define combining rules for Emix, Vmix, and to use the equation of state to calculate properties of a mixture. In this development we again use the so-called van der Waals-1 rules. These assume random mixing of the components, as they did for small 

The fit of P-x data for the acetone-propane binary system (Gomez-Nieto and Thodos, 1978) is shown in figure 5.9. The best fit of the Sanchez-Lacombe 

The calculated cloud point curve for the EMAgg/aj-propane system is shown in figure 5.10. The best fit of the experimental data was obtained with kjj = 0.023 and i7,y = -0.002. If kij becomes more positive, the curve shifts to higher pressures if 17,y becomes more positive, the curve shifts to lower pressures. But the shift in the curve and its slope are more sensitive to changes in 17,y than A ,y. 

It is not possible to determine values for the two mixture parameters for the EMAf,y/3i-acetone mixture because there are no binary data available in the literature for these mixtures. To minimize the number of adjustable parameters, 77,y is set equal to zero. Since EMA g/ai is slightly soluble in 

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The use of supercritical fluids to extract the cyclic ethers from the polymerizate is described. In one example it is related that a charge of THF-ethylene oxide polymerizate containing 8% cyclic ethers is contacted in batch continuous mode with propylene at 100 °C and 83 atm. The residual polymerizate contains 2% cyclic ether content. No gas volume is given in this example or in the three other examples with other polymers and copolymers extracted using supercritical ethylene and propylene. Thus, no distribution coefficients can be calculated to determine the potential industrial value of this patent. 

Adidharma and Radosz provides an engineering form for such a copolymer SAFT approach. SAFT has successfully applied to correlate thermodynamic properties and phase behavior of pure liquid polymers and polymer solutions, including gas solubility and supercritical solutions by Radosz and coworkers Sadowski et al. applied SAFT to calculate solvent activities of polycarbonate solutions in various solvents and found that it may be necessary to refit the pure-component characteristic data of the polymer to some VLE-data of one binary polymer solution to calculate correct solvent activities, because otherwise demixing was calculated. GroB and Sadowski developed a Perturbed-Chain SAFT equation of state to improve for the chain behavior within the reference term to get better calculation results for the PVT - and VLE-behavior of polymer systems. McHugh and coworkers applied SAFT extensively to calculate the phase behavior of polymers in supercritical fluids, a comprehensive summary is given in the review by Kirby and McHugh. They also state that characteristic SAFT parameters for polymers from PVT-data lead to... 

In our investigation into the chemical modification of swollen polymer particles in supercritical fluids, PBT with 44 mmol kg carboxyHc acid end groups was modified with 1,2-epoxybutane in supercritical CO2 or in a supercritical or sub-critical mixture of CO2 with 10 mol% 1,4-dioxane. The critical pressures (Pc) and temperatures (TJ of CO2, and the Pc and Tc values for mixtures of CO2 with 10 mol% 1,4-dioxane, calculated using Ka/s rule [79], have been given in Section 13.3.1. 

Saeki, S. (1997) Calculation of the phase diagram of polymer solution over supercritical fluid region based on the Patterson-Delmas theory of corresponding state. Fluid Phase Equilib. 136,87-92. 

There is a similar expression for polymer activity. However, if the fluid being sorbed by the polymer is a supercritical gas, it is most useful to use chemical potential for phase equilibrium calculations rather than activity. For example, at equilibrium between the fluid phase (gas) and polymer phase, the chemical potential of the gas in the fluid phase is equal to that in the liquid phase. An expression for the equality of chemical potentials is given by Cheng (12). 

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