Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

In-situ quantitative Raman spectroscopy combining with high pressure optical capillary cell was used to measure water solubility in CO2 at pressures from 10 to 50 MPa and temperatures from 313.15 to 473.15 K. To accurately calibrate Raman system for measuring the concentrations of dissolved water in supercritical CO2 at high pressure and elevated temperature, the unsaturated homogenized solution method that we used for measuring the CO2 concentration in aqueous solution previously was modified to obtain the quantitative relationship between composition (the mole fraction of H2O in the homogeneous phase, xH2O) and Raman peak area ratio (PAR). The Raman quantitative factor PAR/xH2O increases linearly with increasing temperature, deceases with increasing pressure, and is not affected by the mole fraction of H2O in the mixture. 45 solubility data points were obtained, and they are generally consistent with previous experimental studies. However, predictions of the thermodynamic models substantially deviate from the new measurements due to the previous lack of accurate experimental data in these P-T ranges. Parameters of the model were then refined, and the solubility data can now be accurately reproduced by the model.