(685f) Steam-Stripping for Regeneration of Supported Amine-Based CO2 Adsorbents

Among the various classes of solid CO2 sorbents being considered for future applications in carbon capture and sequestration, supported amines have many promising features, such as operation at low temperatures (ambient ? 120 °C), high selectivity for CO2, owing to strong CO2:sorbent interactions (50-105 kJ/mol), and the potential for low material costs. In contrast, most other low temperature adsorbents such as zeolites, carbons and (some) MOFs rely on weaker, physisorption interactions, making water, a common component in flue gas, out-compete CO2 for adsorption cites in many cases. Indeed, there are over 70 publications [1] in the open literature that explore the CO2-adsorption properties of supported amine adsorbents.

However, to be a practical CO2 sorbent, the material must be demonstrated to be regenerable in a cost-effective way. Unfortunately, the singular focus of the academic community to date has been on design of high capacity adsorbents, with nearly all published studies focusing entirely on the capture step. Adsorbents are routinely shown to be at least partly regenerable, but almost always via temperature swing with an inert gas purge, which ultimately does not result in a separation. Of course, this regeneration method is entirely impractical in a real process and nearly all previous published research, including our own, has not effectively concentrated the CO2, or performed a useful separation. Thus, a critical missing link in the development of supported amine CO2-adsorbents are studies of potentially practical desorption processes.

We assert here that steam stripping is one of the most promising methods for practical regeneration of supported amine sorbents. Steam stripping provides both (i) a thermal driving force for desorption and (ii) a partial pressure driving force, as in the case of inert gas temperature swing. More importantly, the product stream, containing only CO2 and water, can be easily purified by compression and condensation, removing the water as a liquid to produce a highly concentrated CO2 gas stream, suitable for sequestration or other uses. In this presentation, we will describe a series of tests of all three major classes of supported amine sorbents in cyclic capture-steam regeneration experiments. These include Class 1 adsorbents, based on porous supports impregnated with monomeric or polymeric amines, [2] Class 2 sorbents based on amines that are covalently linked to the solid support, [3] and Class 3 sorbents, which are comprised of porous supports upon which aminopolymers are polymerized in-situ, starting from an amine-containing monomer. [4]

[1] S. Choi, J. H. Drese, C. W. Jones, ChemSusChem 2009, 2, 796-854. [2] X. C. Xu, C. S. Song, J. M. Andresen, B. G. Miller, A. W. Scaroni, Energy Fuels 2002, 16, 1463-1469. [3] T. Tsuda, T. Fujiwara, J. Chem. Soc.-Chem. Comm. 1992, 1659-1661. [4] J. C. Hicks, J. H. Drese, D. J. Fauth, M. L. Gray, G. G. Qi, C. W. Jones, J. Am. Chem. Soc. 2008, 130, 2902-2903.