Measurement and modeling for solubility of 3-hydroxybenzaldehyde and its mixture with 4-hydroxybenzaldehyde in supercritical carbon dioxide

• Solubility of 3-HBA and its mixture with 4-HBA was measured in SCCO2.
• The effect of relative position of functional groups on solubility was analyzed.
• The maximum separation factor and separation efficiency of mixture are obtained.
• A new model was proposed and tested by 636 group solute mixture solubility data.

To understand the phase behavior of 3-hydroxybenzaldehyde (3-HBA) and the solubility effect of 3-HBA and 4-hydroxybenzaldehyde (4-HBA) on each other in supercritical carbon dioxide (SCCO2), the equilibrium solubility of 3-HBA and its mixture with 4-HBA, was measured in SCCO2 binary system (comprising of a solute and SCCO2) and ternary system (comprising of two solutes and SCCO2) at temperature and pressure given in range of 308–328 K and 11.0–21.0 MPa respectively. Comparing the solubility of 3-HBA and 4-HBA between in the binary system and ternary system, it was found that the equilibrium solubility of both 3-HBA and 4-HBA was enhanced in the ternary system due to the molecular interaction. The experimental data were correlated by Chrastil, Mendez-Santiago and Teja (M-S-T), Sovova, their modified models, and Zhu et al. model. Also a new model was deduced and established based on the Chemistry Association Theory and was verified by 636 groups of solubility data. The correlated results indicated that the new model obtained a less deviation than other models, including the modified Chrastil model, the modified M-S-T model, the modified Sovova model, and Zhu et al. model, all of which have same adjustable parameters.

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