Synergistic enhancement of direct air capture by dual-amine functionalized γ-Al2O3 and high gravity adsorption in a rotating adsorption bed

[Geoengineering News]

https://www.sciencedirect.com/science/article/pii/S1383586626027206

Authors: Keju An, Dylan Wald, Kejun Chen, Ryan King

Abstract 

Direct air capture (DAC) is fundamentally constrained by the extremely low concentration of atmospheric CO 2 , which leads to slow adsorption kinetics and poor utilization of adsorption sites. While considerable efforts have been devoted to developing high-capacity amine sorbents, the role of process intensification in overcoming mass-transfer limitations remains insufficiently explored. In this work, a dual-amine PEI-TEPA functionalized γ-Al 2 O 3 adsorbent was coupled with a rotating adsorption bed (RAB) to simultaneously optimize sorbent properties and gas–solid mass transfer for DAC applications. The optimized PEI-TEPA-Al 2 O 3 adsorbent achieved a CO 2 uptake of 52.83 mg۰g −1 , outperforming the corresponding PEI- and TEPA-functionalized adsorbents. High gravity operation substantially accelerated CO 2 capture, and the best adsorption performance was obtained at a high gravity factor(β) of 4.17. Further increases in β resulted in a slight performance decline, indicating a balance between mass-transfer enhancement and gas–solid contact time. Compared with conventional fixed-bed operation, the RAB significantly improved adsorption kinetics, while kinetic analysis showed that the Avrami model provided the best description of the adsorption process. Moreover, the adsorbent retained 87.6% of its initial adsorption capacity after ten adsorption–desorption cycles using steam regeneration at 105 °C. The enhanced DAC performance is attributed to the synergistic integration of dual-amine functionality, preserved mesoporous transport pathways, and high gravity intensified gas–solid mass transfer. This work demonstrates that coupling rational sorbent design with process intensification is a more effective strategy than material optimization alone for atmospheric CO 2 capture, providing a promising route toward compact and high-efficiency DAC systems.

Source: ScienceDirect