Properly designed amine-modified materials exhibit high CO2 adsorption capacity, fast adsorption and desorption, low energy requirement for recycling as well as excellent tolerance of water vapor in the gas feed. However, despite the utmost importance of the long term stability of such materials, no studies addressed this issue through extensive recycling. The lifetime of adsorbents, which determines the frequency of their replacement, is a critical property of equal importance as adsorption capacity, selectivity and kinetics, with direct impact on the economics of commercial scale operations. Here, we used two classes of amine-containing adsorbents for CO2 removal, namely (i) materials with surface-anchored amine species prepared by aminosilane grafting [1-3], and (ii) polyethylenimine-impregnated mesoporous silica . We showed that under dry CO2 adsorption-desorption cycling, amine-containing materials ultimately deactivate even under very mild conditions. We also established that deactivation occurs via the formation of urea groups, and provided a method to dramatically enhance the stability of such materials, using moisture-containing gaseous streams. Furthermore, it was demonstrated that deactivated materials may be fully regenerated via urea hydrolysis. The current findings provide a straightforward strategy to using amine-containing CO2 adsorbents under conditions of unprecedented stability .
References 1. Harlick, P. J. E.; Sayari, A. Ind. Eng. Chem. Res. 2007, 46, 446 2. Belmabkhout, Y.; Sayari, A. Adsorption 2009, 15, 318. 3. Belmabkhout, Y.; Serna-Guerrero, R.; Sayari, A. Ind. Eng. Chem. Res. 2010, 49, 359. 4. Ma, X.; Wang, X.; Song, C. J. Am. Chem. Soc. 2009, 131, 5777. 5. Sayari, A.; Belmabkhout, Y. J. Am. Chem. Soc. 2010 DOI: 10.1021/Ja.1013773