Phase behavior of (CO2 + H2) and (CO2 + N2) at temperatures between (218.15 and 303.15) K at pressures up to 15 MPa

Vapor–liquid equilibrium data are reported for the binary systems (CO2 + H2) and (CO2 + N2) at temperatures between (218.15 and 303.15) K at pressures ranging from the vapor pressure of CO2 to approximately 15 MPa. These data were measured in a new analytical apparatus which is described in detail. The results are supported by a rigorous assessment of uncertainties and careful validation measurements. The new data help to resolve discrepancies between previous studies, especially for the (CO2 + H2) system. Experimental measurements of the three-phase solid–liquid–vapor locus are also reported for both binary systems.

The vapor–liquid equilibrium data are modeled with the Peng–Robinson (PR) equation of state with two binary interaction parameters: one, a linear function of inverse temperature, applied to the unlike term in the PR attractive-energy parameter; and the other, taken to be constant, applied to the unlike term in the PR co-volume parameter. This model is able to fit the experimental data in a satisfactory way except in the critical region. We also report alternative binary parameter sets optimized for improved performance at either temperatures below 243 K or temperatures above 273 K. A simple predictive model for the three-phase locus is also presented and compared with the experimental data.