Solubility of 4-Hydroxybenzaldehyde in Supercritical Carbon Dioxide with and without Cosolvents

The operating conditions of measuring the equilibrium solubility of 4-hydroxybenzaldehyde in supercritical carbon dioxide (SCCO2) were chosen at temperatures of (308, 318, and 328) K and five pressure points from (11.0 to 21.0) MPa, while the solubility data in SCCO2 with three different cosolvents (ethanol, ethyl acetate, and acetone) at 0.04 (mol.mol(-1)) were obtained at 318 K and the aforementioned pressure. The solubility of 4-hydroxybenzaldehyde revealed that the presence of cosolvents could greatly improve the dissolving ability of solvent. The solubilities of solutes with five kinds of functional groups substituted for the formyl group (-CHO) of 4-hydroxybenzaldehyde have been investigated on the aspects of melting point and intermolecular force. The data of 4-hydroxybenzaldehyde in pure SCCO2 were successfully correlated with three semiempirical models (Chrastil, Mendez-Santiago, and Teja (M-S-T) and Bartle models) for a deviation of (6.82 to 8.50) %, while the data with cosolvents were calculated by three different models (modified Chrastil, modified M-S-T, and Sovova models) for a deviation of (2.98 to 8.87) %. The thermodynamic properties of 4-hydroxybenzaldehyde were investigated.