Multiphase high pressure equilibria in ternary aqueous systems

Experimental phase equilibrium measurements for the ternary system carbon dioxide - n-butanol - water are presented at 313 and 333 K and pressures from 2 to 15 MPa. The system exhibits extensive three-phase equilibrium regions. Equilibrium between four fluid phases was observed at 313 K and 8.25 MPa total pressure. A new density-dependent mixing rule with a cubic equation of state is proposed for modelling the experimental results. The model reproduces quantitatively many features of the experimentally observed behavior.