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 tolerance to water. 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 sites in many cases.
The benchmark method for CO2 capture from gas streams uses aqueous amine solutions (e.g. ~20-40% monoethanolamine and ~60-80% water) to absorb CO2 and this approach has been suggested for CO2 capture from power plant effluents. From decades of development of this technology, it is known that amine oxidation is an issue that directly impacts of economics of amine-based CO2 absorption processes, and hence, similar issues might be expected to manifest themselves in adsorption processes that use solid-supported amines.
To this end, we describe here a series of tests on all three major classes of supported amine sorbents aimed at assessing the stability of silica-supported amine adsorbents in steaming and oxidative steaming conditions. These include Class 1 adsorbents, based on a porous supports impregnated with monomeric or polymeric amines,  Class 2 sorbents based on amines that are covalently linked to the solid support,  and Class 3 sorbents, which are comprised of porous supports upon which aminopolymers are polymerized in-situ, starting from an amine-containing monomer.  In this work, a highly porous mesocellular foam silica is used as the substrate for sorbents of all three classes described above. The impact of the oxidative steaming conditions on adsorbent structure and CO2 adsorption properties will be reported.
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