(320e) Influence of Metal Contaminants on Solid Amine Sorbents for Direct Air Capture

Direct Air Capture (DAC) of CO₂ from the air via adsorption is a promising technology to address current and historic CO₂ emissions. Amine-containing sorbents have demonstrated potential for capturing CO₂ from ambient air due to their high CO₂ adsorption selectivity. However, existing research on amine-based DAC adsorbents has been primarily conducted under ideal conditions with clean feed streams, neglecting the influence of impurities present in real-world applications. Contaminants may strongly interact with the surface functional groups of adsorbents, affecting their performance and structural integrity. Metal ion species are of particular importance as potential impurities, as even trace amounts may catalyze amine oxidation. This study aims to explore the influence of transition metal species such as Cu²⁺, Fe²⁺, and Ni²⁺ on the CO₂ uptake performance and oxidative degradation of an aminopolymer-impregnated silica sorbent (30 wt.% poly(ethyleneimine) (PEI)/SBA-15). Our ongoing research investigates the effect of various metal-loading concentrations on the CO₂ adsorption capacity of both fresh and oxidized adsorbents, employing IR spectroscopy to gain deeper insights into the catalytic effect of the metals on amine oxidation. We observe that metals can deactivate the adsorbent by poisoning the available amine sites. Moreover, exposure of the adsorbent to air at elevated temperatures demonstrates that the presence of metals significantly accelerates amine oxidative degradation that seems to follow a radical-initiated autoxidation mechanism.