Phase Equilibria of Glycerol Tristearate and Glycerol Trioleate in Carbon Dioxide and Sulfur Hexafluoride

Abstract

Phase equilibria of 1,3-di(octadecanoyloxy)propan-2-yl octadecanoate (glycerol tristearate) and 2,3-bis[[(Z)-octadec-9-enoyl]oxy]propyl (Z)-octadec-9-enoate (glycerol trioleate) in carbon dioxide and sulfur hexafluoride have been investigated. Compositions of the equilibrated phases have been determined experimentally at pressures up to 51 MPa in a variable-volume view cell. The solubility of glycerol tristearate in CO2 and SF6 was determined at temperatures (333, 343, and 363) K and over a pressure range from (1.6 to 45.1) MPa for CO2 and (1.6 to 31.0) MPa for SF6. The solubility of glycerol trioleate in CO2 and SF6 was measured at (333, 343 and 363) K and pressures up to 51 MPa. For the systems of triglyceride in CO2, the experimental data are in a good agreement with literature data. For glycerol tristearate-SF6 and glycerol trioleate-SF6 systems, the phase inversion was visually observed at all temperatures. Furthermore, the solid–liquid (S-L) phase transition of glycerol tristearate in CO2 and SF6 was investigated by using a high-pressure view cell. For both systems the three-phase solid–liquid–vapor (S-L-V) line with a temperature minimum in the p–T diagram was observed. High-pressure differential scanning calorimetry (HP DSC) was used to measure and compare the melting point of glycerol tristearate in CO2 with the results obtained by observation in a view cell.