Minimizing the effect of oxygen on supported polyamine for direct air capture

Direct air capture (DAC), as a typical technology of negative emission technologies, is indispensable to neutralizing mobile carbon emissions. The polyamine-loaded adsorbent with high CO₂ capacities at extremely low CO₂ concentration while maintaining mild regeneration conditions is a promising choice for actual DAC systems. This work comprehensively investigated the effect of oxygen in the air on the selectivity of polyamine-functionalized adsorbents towards CO₂ in the adsorption process and the oxidative stability in the desorption process. Results indicate high selectivity toward CO₂ and oxidative resistance of adsorbents can be realized by accurately controlling the operating temperature. The oxidation of supported polyamine follows a three-phase mechanism. The oxidative stability of adsorbents varied at oxidation phases distinguished by different operating temperatures. Instructed by that three-phase oxidation mechanism, the optimal regeneration temperature of 80 °C was suggested for supported PEI and TEPA adsorbents. This optimal regeneration temperature can achieve favorable CO₂ capture performance and maintain superior oxidative stability. Based on these findings, an air-assisted temperature swing adsorption DAC system was proposed to collect CO₂ from the air for agricultural greenhouse.