An Up Side to Humidity

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Science  14 May 2010:
Vol. 328, Issue 5980, pp. 793
DOI: 10.1126/science.328.5980.793-c

Concerns over the climatic impact of rising CO2 levels in the atmosphere have led to a flurry of research activity directed toward capturing the gas as it's released from power plants and ultimately burying it in the ground. An efficient process along these lines would require a sorbent that attracted CO2 vigorously and quickly, yet formed a weak enough bond to facilitate release into a concentrated stream bound for the sequestration well. Sayari and Belmabkhout show in this context that humidifying a CO2 stream helps to maintain the robustness of amine-bearing solid sorbents. Through solid-state nuclear magnetic resonance spectroscopy, the authors found that dry CO2 can react with two amine sites, forming a urea [N−(C=O)−N] linkage with concomitant loss of water that traps the carbon too tightly and inhibits regeneration of the free sorbent. Adding water restricts the binding motif to a single N-C bond, which is more easily broken on heating, allowing more than 700 sorption/desorption cycles without substantial efficiency loss. Moreover, deactivated sorbents could be regenerated by day-long heating under humid N.

J. Am. Chem. Soc. 132, 10.1021/ja1013773 (2010).

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