(88f) Recovery Of Organic Compounds From Ionic Liquids By Anti-Solvent Crystallization With Carbon Dioxide

A relatively unexplored option that can be used to recover organic compounds from ionic liquids (ILs) is crystallization. So far, most crystallizations from ILs were carried out in combination with a reaction step, where the product precipitates upon reaction, as the reactants have a higher solubility in the IL than the product. Another method to crystallize a product from an IL described previously is the use of an additional co-solvent that increases the solubility of the product in the IL and is evaporated in a second step in order to induce crystallization. Here, we show that it is also possible to recover organic compounds from ILs by anti-solvent crystallization using carbon dioxide (CO2) as anti-solvent. As an example, the crystallization of the organic compound methyl-(Z)--acetamido cinnamate (MAAC) from the IL 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim+][BF4-]) using supercritical CO2 as anti-solvent is studied experimentally. It was found that MAAC can be recovered from [bmim+][BF4-] by either using a shift to higher CO2 concentrations at equal temperature (anti-solvent crystallization) or by using a shift to lower temperatures at equal CO2 concentration (thermal shift).