Detection and measurements of high pressure VLE and LLE - PvT data of binary mixtures through the vibrating tube densitometer technique

In this work we analyze the feasibility of detecting equilibrium states and measuring, simultaneously, saturated liquid densities and equilibrium pressures at fixed temperature, of "Type V" binary mixtures in state regions where both VLE and LLE are present. The employed technique is the Synthetic Indirect PvT Method through a single vibrating tube densitometer setup. The detection of phase equilibrium is performed by analyzing the topology of near continuous isothermal data acquisitions in the vicinity of the discontinuous phase transition at a saturation point. Close to the estimated equilibrium pressure, a flow rate of about 0.0002 MPa/s is set within the measuring instrument preserving the temperature stability, and the periods of vibration of the densitometer are sampled and registered every 3s. The collected data are analyzed by means of mathematical interpolations, and the data corresponding to the location of a change in the slope or in the curvature of the isothermal behavior is pointed out. We present examples of the topologies and data analysis obtained for synthetic mixtures of Ethane + n-Propan-ol at different temperatures in the region where they present liquid-liquid in-miscibility encompassing LLE and VLE at near critical conditions. The equilibrium data are discussed and compared with those available in the literature.