Renormalization group theory for fluids including critical region. II. Binary mixtures

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, 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 temperature. 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 theories, applicable to the whole phase equilibrium region of binary mixtures.