(154i) Engineering Reactions with Ionic Liquids

Ionic liquids are salts with low melting points. They are attractive as solvents for gas separations due to their low volatility, wide liquid operating range, extremely low vapor pressures and thermal stability. More importantly, their structure and, therefore, affinity for various gases can be tuned almost limitlessly by judicious choice of anion, cation and substituents. While the solubility of CO2 in many ionic liquids is significantly higher than other gases, the capacity is not sufficient for post-combustion CO2 separation due to the low CO2 partial pressures available. Therefore, we have incorporated amine functionality into the ionic liquids to react with CO2. By putting the amine in the anion, we show that high capacities, up to one mole of CO2 per mole of ionic liquid, are possible. Unfortunately, when many amine-functionalized ionic liquids react with CO2, they exhibit a dramatic increase in viscosity. Here we show how this problem can be ameliorated by careful choice of the anions. Finally, we present results for the rates of reaction of amine-functionalized ionic liquids with CO2.