Direct air capture (DAC) of CO₂ has garnered significant attention as a promising net-negative emission technology to combat global climate change. DAC's deployment-location flexibility enables integration with various CO₂ utilization or storage processes, facilitating on-site CO₂ production tailored to specific industrial or geographic needs. Amine-functionalized solid adsorbents are particularly advantageous for DAC applications due to their high affinity to CO₂, enabling efficient capture even at low atmospheric concentrations and regeneration at moderate temperatures (<100°C). Recent developments have introduced structured sorbent configurations, including fiber, honeycomb monolith, and laminate sheet form factors. These designs optimize air-flow distribution and minimize pressure drop, thereby enhancing the gas-solid contact area and reducing energy consumption during the adsorption-desorption cycle. Deployment of such structured sorbents enables rapid processing of large air volumes, offering substantial reductions in energy consumption and operational costs, making DAC a scalable solution for achieving significant CO₂ removal at industrial scale, contributing to global net-negative emission targets.
We developed structured sorbents from expanded PTFE (ePTFE) with embedded aminosilica particles to create unique structured contactors [1] that show promising CO₂-capture performance. To simulate global environmental conditions, we evaluated performance of low, medium, and high PEI-loading ePTFE/silica samples over a broad temperature range of -20°C to 35°C and varying relative humidity between 0-80%. When humidity was increased to 50% RH at sub-ambient temperatures of -20°C and 5°C, CO₂ adsorption capacity significantly increased from 0.7–1.0 mmol CO2/gsorbent to 2.5–3.0 mmol CO2/gsorbent, whereas the humidity effect was minimal at higher temperatures, such as 35°C. CO₂ uptake and sorption kinetics were found to vary depending on the PEI loading. These results suggest the importance of selecting appropriate sorbents based on environmental conditions for optimal DAC performance.
References:
[1] Y.J. Min. A. Ganesan, M.J. Realff, C.W. Jones, ACS ACS Appl. Mater. Interfaces, 14 (36), (2002) pp.40992-41002.
