Density Measurements of the H2–CO2–CH4–CO–H2O System by the Isochoric Method at 722–930 K and 15.4–30.3 MPa

The density of the H2–CO2–CH4–CO–H2O system in the supercritical region of water is significant for analyzing the gasification process of organic substances in the supercritical water. We report density measurements of the quinary system by the isochoric method at 722–930 K and 15.4–30.3 MPa. The upper limit of the expanded uncertainty at 95% confidence for temperature is 0.2 K. The upper limits of the expanded relative uncertainties at 95% confidence for pressure and density are 0.0006 and 0.0125, respectively. The density data were compared with those predicted using the GERG-2008 equation of state. The absolute relative deviations between the calculated and experimental densities are not more than 1.79%. Furthermore, the excess volume of the quinary system decreases monotonically with the increase of temperature in the isochoric process at 722–930 K. The thermal expansion coefficients of the quinary system were also determined.