(255a) Solvent Effects in Ionic Liquid Production in Conventional and Dense-Phase C O2 Systems
Ionic liquids have been touted as the next great class of environmentally-friendly solvents due to their lack of vapor-pressure and molecularly ?tunable? properties. New applications are being developed at a rapid pace. However, reports of their synthesis almost always include the very solvents that they will purportedly replace. Moreover, ionic liquids are currently too costly to utilize them as an alternative solvent in large-scale industrial processes. This is primarily due to small batch production and nearly non-existent kinetic and thermodynamic data of their synthesis which has resulted in no emphasis on reactor engineering and process intensification. For ionic liquids to be truly ?green? and to be used ubiquitously, they themselves must be made in a corresponding benign way in potentially large quantities and for low cost. This study will illustrate how molecular level understanding of the synthesis of ionic liquids in conventional solvents and environmentally-benign compressed CO2 can lead to optimized production strategies. The bimolecular rate constants of several classes of cations have been determined and shown to be highly solvent dependent. Solvatochromic probes have been used to characterize the ?polarity? of these solutions. Compressed CO2 has been shown to be an attractive tunable reaction/separation medium. By understanding the phase behavior, the kinetics and separations can be simultaneously optimized in this environmentally-benign medium.