Investigation Of The Phase Equilibria For CO₂-methanol And CO₂-ethanol Binary Mixtures

A cross-association model was proposed for CO₂-alcohol mixtures based on the statistical associating fluid theory (SAFT). CO₂ was treated as a pseudo-associating molecule and both the self-association between alcohol hydroxyls and the cross-association between CO₂ and alcohol hydroxyls were considered. The equilibria properties from low temperature-pressure to high temperature-pressure were investigated using this model. The calculated p–x and p–ρdiagrams of CO₂-methanol and CO₂-ethanol mixtures agreed with the experimental data. The results showed that when the cross-association was taken into account for Helmholtz free energy, the calculated equilibrium properties could be significantly improved, and the error prediction of the three phase equilibria and triple points in low temperature regions could be avoided.