Solubility of hexanoic acid and butyl acetate in supercritical carbon dioxide

The solubility of hexanoic acid (HA) and butyl acetate (BA) in supercritical carbon dioxide in a pressure range of 75–180 bar and a temperature range of 313–353 K were measured. The two compounds have the same molecular weight (116.16 g/mol), but the polarity (i.e. the permanent electric dipole moment) and boiling point of HA was higher than BA (475 K for HA and 399 K for BA). The solubility of HA and BA was also measured at different flow rates of supercritical carbon dioxide and sample loading (i.e. solute) in the equilibrium cell. The solubility of BA in supercritical carbon dioxide was found to be higher than of HA. This is due to its weak intermolecular interactions and high volatility. The trend of the solubility versus temperature was to be found different for the two compounds above 323 K at a pressure of 123 bar.