Solubility of azelaic acid in supercritical carbon dioxide

In this study, the solubility of azelaic acid in supercritical carbon dioxide has been measured at 313.15 K and 333.15 K over a pressure range of 10 MPa to 30 MPa. A flow-type, dynamic apparatus was used, and the solubility was obtained gravimetrically. The solubility ranged from an azelaic acid mole fraction of 0.42 center dot 10(-6) (333.15 K, 10.0 MPa) to 10.12 center dot 10(-6) (333.15 K, 26.7 MPa). The solubility results showed that the crossover point occurred at a pressure between 17 MPa and 20 MPa; at pressures below the crossover pressure, the solubility decreased with increasing temperatures, whereas the opposite was observed beyond the crossover pressure. No solubility data for azelaic acid in any supercritical fluids were found in the literature; thus, there was no reference to compare these results. Two model types were used to correlate the data: density-based models and an equation-of-state (EoS) model. The Chrastil and the modified Mendez-Santiago and Teja (density-based) models were used, and excellent fits were obtained. The Peng-Robinson EoS with standard van der Waals mixing rules was used also with excellent results.