Reversible Ionic Liquid Stabilized Carbamic Acids: A Pathway Toward Enhanced CO2 Capture
2013
Switzer, Jackson R. | Ethier, Amy L. | Flack, Kyle M. | Biddinger, Elizabeth J. | Gelbaum, Leslie | Pollet, Pamela | Eckert, Charles A. | Liotta, C. L. (Charles Leonard)
Capturing CO₂ from flue gas streams under near ambient conditions—e.g. coal-fired power plants—has traditionally involved the use of aqueous alkanol amine solutions. Aqueous solvent-based processes are energy intensive, as solvent regeneration can be costly. With growing concern over climate change, alternative CO₂ capture technologies that are energy and cost efficient are required. We have established that nonaqueous silylamines can be used to efficiently and reversibly capture and release CO₂ via the formation of reversible ionic liquids. We now report their unique, enhanced CO₂ uptake at room temperature under 1 atm of CO₂, as silylamines exhibit CO₂ capture capacities greater than that expected from the conventional stoichiometry of a 2:1 amine to CO₂ mole ratio. Experimental evidence is presented supporting the formation of a carbamic acid species in equilibrium with an ionic liquid network of ammonium–carbamate ion pairs to give a 3:2 amine to CO₂ mole ratio. This is the first report of the stabilization of carbamic acid by reversible ionic liquids. Stabilization of carbamic acid leads to a significant increase in CO₂ capacity (30% on average) over conventional amine solutions for CO₂ capture.
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