Supercritical fluid carbon dioxide: Reagent solubility, phase behavior and purification studies

Supercritical fluid carbon dioxide (SCF CO2 is an attractive alternative for traditional solvents in green chemistry. However, commercial exploitation of SCF CO2 technology has been relatively limited due to the lack of fundamental data on SCF CO2 solute systems. The purpose of this research was to investigate single and multicomponent SCF CO2 solute systems and to present an application of SCF CO 2 extraction.; A reliable experimental method was developed to measure solubilities of solutes. Benzoic acid, salicylic acid and acetylsalicylic acid were chosen as model polar solutes and their solubilities in SCF CO2 were investigated in binary, ternary and quaternary systems over a range of temperatures (308 K--318 K) and pressures (101--280 bars). Mixed polar solute systems demonstrated solubility enhancements consistent with the entrainer effect. A study on benzoic acid + salicylic acid + fluoranthene quaternary system demonstrated that solute-solute interactions can be specific and can result in an increase in the solubility of solutes and the selectivity of SCF CO 2.; Solubilities of selected industrially important substituted phenols (2,3-dimethyl phenol, 2,5-dimethyl phenol, 2,3,5-trimethyl phenol, 2,4,6-trimethyl phenol, 4-tert-butyl phenol, and 4-phenyl phenol) were investigated in binary and ternary systems in the pressure range of 101--280 bar at 308 K.; In order to ensure that only solid-fluid equilibrium existed under the experimental conditions used for solubility studies, phase behavior of all the systems was investigated using a view cell apparatus. For all solute systems, lower critical end point (LCEP) was determined and the possible depression in melting point was checked. Under the conditions investigated, the majority of the systems exhibited solid-fluid equilibrium with no liquid phase present.; Purification of a colored 2,3-DMP commercial reagent using SCF CO 2 extraction has been investigated at different temperatures and pressures. Extraction at 328 K and 91 bar gave a white 2,3-DMP product with high purity. Purification was possible due to the differential solubility of the 2,3-DMP and the impurities in SCF CO2. The less soluble dark colored impurities were found to be high molecular weight compounds. Two major impurities have been isolated and identified using GC-MS, IR, 1D, and 2D NMR spectroscopy.