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 equilibrium properties from low temperature-pressure to high temperature-pressure were investigated using this model.The calculated p-x and p-p diagrams 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.
FU Dong,YANG Zhuang,LU JianYi & LIU JianMin School of Environmental Science and Engineering,North China Electric Power University,Baoding 071003,China
The excess Helmholtz free energy functional for nonpolar chain-like molecules is formulated in terms of a weighted density approximation （WDA） for short-range interactions and a Weaks Chandler Andersen （WCA） approximation and a Barker Henderson （BH） theory for long-range attraction. Within the framework of density functional theory （DFT）, vapour liquid interracial properties including density profile and surface tension, and vapour-liquid nucleation properties including density profile, work of formation and number of particles are investigated for spherical and chain- like molecules. The obtained vapour liquid surface tension and the number of particles in critical nucleus for Lennard- Jones （L J） fluids are consistent with the simulation results. The influences of supersaturation, temperature and chain length on vapour liquid nucleation properties are discussed.
