THERMODYNAMIC PROPERTIES OF MIXING FOR SNCL4 DISSOLVED IN SUPERCRITICAL CO2 - A COMBINED EXPERIMENTAL AND MOLECULAR-DYNAMICS STUDY

Enthalpies and volumes of mixing were measured as a function of composition for mixtures of SnCl4 in supercritical CO2 at two temperatures (313.15 and 348.15 K) above the critical temperature of pure CO2 and at four pressures (6.29, 8.36, 10.44 and 12.50 MPa) spanning the critical pressure of CO2. Molecular dynamics simulations were performed at the same conditions, modeling SnCl4 as a Lennard-Jones fluid and CO2 as a two-site fluid interacting with Lennard-Jones potentials. Quite simple molecular interaction models are capable of reproducing the large pressure dependence observed in both the mixing volume and enthalpy data in the critical region of pure CO2. Additionally, Widom's method was used to obtain the excess free energies of the mixtures. Simulated vapor-liquid equilibrium for conditions below the mixture critical locus is in qualitative agreement with phase boundaries obtained from the experimental heat of mixing data.