AIChE Journal, Vol.52, No.1, 342-353, 2006
Prediction of global VLE for mixtures with improved renormalization group theory
The recently proposed renormalization group (RG) theory is reformulated within the context of density functional theory and applied to predicting global vapor-liquid equilibria (VLE) of Lennard-Jones chain pure fluids and fluid mixtures. An accurate equation based on the solution of the first-order mean-sphere approximation (FMSA) is adopted outside the critical region. Inside the critical region, the direct correlation function of FMSA is incorporated into the new RG transformation to describe the long-range fluctuation, which is conformal to general inhomogeneous studies. The new RG theory is applied to correcting real mixture phase envelopes, as well as corresponding phase diagrams of pure compounds for the critical region. The calculated results are in substantial agreement with those from experiment and molecular simulation both inside and outside the critical region. The new method is highly predictive because no adjustable parameters and no mixing rule are needed for both model and real fluid mixtures. (c) 2005 American Institute of Chemical Engineers.