Experimental Procedure for Measuring Solid-Liquid-Gas Equilibrium in Carbon Dioxide + Solute

The aim of this work is to report an experimental procedure for measuring solid-liquid-gas phase equilibrium behavior for binary systems constituted by carbon dioxide + solute. Our proposed measuring procedure depends on solid formation detection from fluid phases by a pressure change. The experimental apparatus uses a stainless steel cell where windows are not required. The mixture is slowly cooled while temperature and pressure are decreasing at isochoric conditions. Therefore, the solid-liquid-gas phase equilibrium data are considered when pressure exhibits an abrupt increase while temperature is still decreasing. The studied solutes are lauric acid, myristic acid, palmitic acid, and stearic acid. Besides, additional solid-liquid-gas equilibrium data are included for the same systems using an apparatus recently reported by our working group which is based on the enhanced first freezing point technique. Experimental results are represented using the Peng-Robinson equation of state coupled to the van der Waals one-fluid mixing rules with two adjustable parameters.