Exploring the Acid Gas Sorption Properties of Oxidatively Degraded Supported Amine Sorbents

Amine-supported mesoporous oxide materials have proven to be effective acid gas sorbents. While the primary application of these supported amine species has been CO ₂ capture, they have also shown to be proficient at adsorbing other damaging flue gas impurities such as SO _x and NO _x . The precise nature of the amine (primary, secondary, or tertiary) is known to dictate the gas-amine interactions, with tertiary amines of particular interest due to their inability to adsorb dry CO ₂ , favoring SO _x and NO _x species. The different amine sites also provoke differences in oxidative stability, when exposed to temperatures similar to those used for thermal desorption procedures. Herein we focus on the structural and chemical changes that occur in a range of class 1 (amine-impregnated) and class 2 (amine-grafted) sorbents upon oxidation and correlate these with their variation in acid gas (CO ₂ , NO ₂ , and SO ₂ ) uptakes, as a function of the oxidation temperature. These studies suggest that oxidatively degraded or "spent" supported amine materials may have possible uses as NO _x or SO _x sorbents. Specifically, despite oxidative degradation these aminopolymer species maintain a reasonable level of NO ₂ uptake, despite losing the ability to capture SO ₂ or CO ₂ , offering unique possibilities in selective NO ₂ capture.