A SAFT equation of state (EOS) combined with eight mixing rules was used to evaluate the capability of the SAFT approach for modeling the solubility of solids in supercritical fluids (SCFs). The results show that the SAFT approach gives good correlative accuracy in general, and the results are satisfactory when the three-parameter mixing rules are used, where the average absolute deviation of solid solubility in the SCF phase is normally smaller than 10%. The present work shows that the SAFT approach can be used to model solid-SCF equilibria, which gives slightly better correlative accuracy than the cubic EOSs.

In our previous work [J. Mi, C. Zhong, Yi.-G. Li, J. Chen, Chem. Phys., 305 (2004) 37-45], an equation of state (EOS) based on the combination of renormalization group theory (RG) and the statistical associating fluid theory (SAFT) was proposed for describing pure fluid thermodynamic properties both inside and outside critical region, which was extended to binary mixtures in this work. A variety of binary systems were considered in this work, including nonpolar/nonpolar, /polar, nonpolar/associating and associating/associating mixtures. Two adjustable parameters are required by the new EOS for each binary system, which are obtained by fitting the vapor-liquid equilibria (VLE) data at one emperature. The calculated results show that the new EOS gives satisfactory predictions for critical properties as well as the VLE at other temperatures, both inside and outside critical region. This work demonstrates that RG theory is a very useful tool for accurately describing fluid properties inside critical region, and a combination of it with SAFT EOS can lead to a new EOS possessing the advantages of both heories, applicable to the whole phase equilibrium region of binary mixtures.

Based on White s renormalization group (RG) theory and the statistical associating fluid theory, a new equation of state (EOS) is derived, which can be used for a variety of fluids, including non-polar, polar and associating chain fluids both inside and outside the critical region. The new EOS, with the advantage of not introducing any additional adjustable parameter to the RG transform for real fluids, yields satisfactory critical exponent, vapor-liquid coexistence densities and vapor pressures, pVT isotherms, and isobaric specific heats for pure fluids. Especially, much better results are obtained than the original EOS in the nearest vicinity of the critical point.

The open-cell model equation of state (OCM EOS) proposed in the preceding paper by the authors has been extended to polymer-solvent and polymer blend systems, covering a variety properties, including P-V-T relations, the excess volume and enthalpy, the activity of solvents, and phase diagrams. Compared with the well-recognized Simha and Somcynsky EOS, the OCM EOS presents a better description of P-V-T relations and phase diagrams. Besides, through a set of proper binary interaction parameters, good correlation of the excess properties can be achieved. In conclusion, as an improvement over the existing hole theory EOSs, the OCM EOS is capable of describing liquid mixture properties with satisfactory accuracy.

An open-cell model equation of state has been proposed, which relaxes the restrictions of the cell theory and allows more flexibilities in describing the structure of liquids. To test its capability, this equation has been applied to a variety of liquids, including 17 heavy molecular weight hydrocarbons, 10 organic solvents, and 15 polymers, in particular. The calculated density grand average AADp for the equation proposed here are 0.062, 0.057, and 0.054 per cent against the results for the equation of state by Simha and Somcynsky, 0.081, 0.093, and 0.072 percent for the above three groups of liquids, respectively. Good agreement between our calculated results and experimental data indicates that our model is an improvement over the Simha and Somcynsky equation of state, which has been evaluated as one of the best equations. Moreover, this equation can be easily extended to describe the properties of polymer solutions and polymer blends, which will be addressed in our subsequent paper.