(Invited) 20 Years of CO2 Capture By Ionic Liquids, Molecular Liquids, and Liquids in-between

Abstract

In 2002 we reported the first synthesis and use of a functionalized ("task-specific") ionic liquid for the reactive but reversible capture of CO2. Our original application target was the use of these salts in natural gas purification. However, in succeeding years considerable fervor grew up around us focused on accomplishing large-scale CO2 capture due to concerns about its contribution to global climate change, and that has since supplanted the former application as a major driver of our research. Recognizing that our early materials were likely prohibitively expensive for large scale use, we then spent five years devising new ones which could be made inexpensively from bulk commodity chemicals. In the time since, work with that class of salts, including the edible-in-principle salt choline taurate, has continued apace. These efforts have now resulted in systems which are being actively assessed by the Navy and NASA for closed-system removal of CO2 from breathing air, and which are being tested at pilot plant scale, in collaboration with Norton Engineering, for industrial emissions gas CO2 capture, as well as CO2 capture from ambient air. A brief discussion of the timeline of these developments will be presented, as will details about the ionic liquids currently being used in these tests and our results to date. In addition, we will briefly discuss the potential for using in-situ electrochemical reduction of CO2 in the 'loaded' ILs as a means to convert them into value-added products. Finally, we will also briefly comment on terminology as it relates to ionic liquids, molecular liquids, and liquids "in-between." Figure 1