Design and Evaluation of Ionic Liquids as Novel CO2 Absorbents. (Quarterly Report, July 1, 2005-September 30, 2005)

摘要

Progress from the fourth quarter 2005 activity on the project Design andEvaluation of Ionic Liquids as Novel CO2 Absorbents is provided. Major activities in three areas are reported: compound synthesis, property measurement and molecular modeling. Two new ionic liquids have been synthesized (1-n-hexy-3-methylimidazolium saccharinate and 1-n-hexy-3-methylimidazolium acesulfumate). Densities and viscosities have been measured for these compounds. A new apparatus for measuring SO2 solubility in ionic liquids was installed, tested and validated. Using this new apparatus, we carried out the first ever measurements of SO2 solubility in an ionic liquid. It was determined that SO2 is remarkably soluble in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluorometha nesulfonyl)imide. We believe this is a general phenomenon and that other ionic liquids will show similar high solubilities. CO2 and N2 solubilities as well as thermal decomposition temperatures were measured in the recently synthesized 1-nhexy- 3-methylimidazolium lactate ionic liquid. This ionic liquid shows some of the highest CO2 solubility of any ionic liquid we have tested. It wasfound, however, that thermal stability may be an issue above 100 oC. To make a better comparison of the performance of the ionic liquids, we have used DOE baseline data for CO2 absorption to compute a relative CO2carrying capacity of the ionic liquids versus MEA. We show that the initial ionic liquids studied likely have too low a capacity to be economically viable, but the new lactate compound is approaching the capacity required. We validated the molecular modeling code for computing absorption isotherms and have results for CO2 absorption in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate.