Thermodynamics Research Center / ThermoML | Fluid Phase Equilibria

ABSTRACT

A continuous flow apparatus with a camera system was modified for high-pressure gas liquid equilibrium measurements. The continuous flow method is suitable for phase equilibrium measure- ments of heat-sensitive materials, such as heavy oils and bio-based feedstocks, which are refined in hydroprocesses at high temperatures and pressures. Benefits of the modified apparatus are a short residence time of a sample in the heated zone and no sampling is required. In contrast, the static method is usually impractical with the heat-sensitive materials due to the long residence time of sample in the equilibrium cell. In this study, the continuous flow apparatus and the measurement method was adopted and validated. The validation was conducted by measuring hydrogen solubility in toluene and nhexadecane at high temperatures and pressures (T = 461 to 575 K, P = 5 to 10 MPa) and comparing the results with the literature values. Relative average pressure deviation was found to be 3.8% for measurements of this work when the PC-SAFT equation of state was optimized against literature values while the relative average pressure deviations for the literature data sets varied from 0.9% to 4.7%. Thus, the quality of measurements was shown to be excellent. In addition, hydrogen solubility was also measured in noctadecane in order to obtain new data for this system. All measured systems were modeled with the PCSAFT and the original and modified Peng Robinson equations of state in order to simplify the validation of the measurement method and to compare the performance of the selected models. PC-SAFT was found to predict phase behavior of the systems precisely whereas the predictions of the Peng Robinson modifications were less precise.