High-pressure phase equilibria for carbon dioxide-methanol-water system: experimental data and critical evaluation of mixing rules

Abstract

Equilibrium phase compositions for the carbon dioxide-methanol-water system were measured at 313.2 K and pressures of 70, 100, and 120 bar. Three-phase equilibria for this system were also measured at 305.15, 308.15, and 311.15 K, temperatures and pressures near the critical point of carbon dioxide. The two- and three-phase equilibrium data were correlated with the Soave-Redlich-Kwong and Patel-Teja equations of state incorporated with various types of the local composition and Huron-Vidal mixing rules. The Huron-Vidal mixing rules were found to be superior to the local composition models in predicting two-phase equilibria. Since the pressure range covering the three-phase region was very narrow, the Huron-Vidal mixing rules could not accurately predict the experimental three-phase equilibria. However, if there were a slight change of pressure in phase calculation, the Huron mixing models could correctly predict the experimental three-phase region and equilibrium compositions