High-pressure phase equilibria and supercritical pVT data of the binary water + methane mixture to 723 K and 200 MPa

The phase equilibria of the binary methane + water mixture are examined at high temperatures and pressures. The experimental molar volumes are reported at temperatures of 653, 673, and 723 K and at pressures from 10 to 200 MPa. Reevaluated data for the critical curve and some binodal coexistence isotherms are reported. The critical curve commences from the critical point of water and rises steeply to high pressures after passing through a temperature minimum. The experimental molar volume and critical points are compared with the values predicted using equations of state. Reasonable agreement between theory and experiment is obtained for the critical pressure-temperature behavior by using only two adjustable parameters. Good agreement is obtained for the analysis of the critical pressure-composition data. Except for calculations at pressures and temperatures in the proximity of the critical point of water, the predicted molar volumes are also in reasonable agreement with experiment. 39 refs., 6 figs., 3 tabs.