High pressure multiphase equilibria in aqueous systems of carbon dioxide, a hydrophilic organic solvent and biomolecules

Abstract

A binary mixture of water and a water-soluble organic solvent which at atmospheric pressure reveals no miscibility gap, can be forced to split into two liquid phases by pressurization with a `near-critical' gas. Since both coexisting liquid phases are water-rich, the liquid phase split might be used, for example, for the recovery of delicate, high value products by means of extraction in biotechnology. An overview is given on the phase behavior of ternary systems water–hydrophilic organic solvent–carbon dioxide, focusing on the high pressure three phase equilibrium LLV. Exemplary experimental results for such phase equilibria are presented, discussed and compared with predictions from an equation of state. Furthermore, new experimental results for the partitioning of vanillin and caffeine to the coexisting liquid phases in high pressure three-phase LLV equilibrium in water–acetone–carbon dioxide at 313 and 333 K are presented together with a simple method for correlating these results.