Carbon nanotube-assisted self-assembly of monolithic CO2 adsorbent: Evaluating the optimum pellet diameter for enhanced mass transfer

초록

Shaping fine particles into pelletized CO2 adsorbents is critical for practical CO2 capture applications. This study presents a scalable carbon nanotube-assisted self-assembly for fabricating CO2 adsorbent pellets with optimized diameter for enhanced mass transfer. At 4 vol% CO2, the resulting pellets exhibit high performance, with only an 8.5 % reduction in total CO2 uptake (from 2.55 mmol g−1 to 2.33 mmol g−1) and a 22.7 % decline in peak adsorption rate (from 15.9 μmol g−1 s−1 to 12.3 μmol g−1 s−1) compared to their powdered counterparts. Remarkably, the pellets maintain a total CO2 uptake of 2.01 mmol g−1 even under dilute CO2 concentrations of 0.04 vol%. The pellets also demonstrate exceptional mechanical properties, achieving a compressive strength of 5.5 MPa and an attrition resistance of 3.6 %, ensuring durability during cyclic operations. These properties are achieved without the need for binders or mechanical pressing, simplifying the fabrication process while maintaining structural integrity. Moreover, a three-step mass transfer model is employed to investigate how variables, including mass flow rate, CO2 concentration, temperature, and pellet size, influence the CO2 adsorption performance of pellet adsorbents. The model reveals that the optimal size of the pellet adsorbents depends on target CO2 concentrations and application-specific conditions. The pellet radius should not increase beyond 0.075 cm and 0.05 cm under 4 vol% and 0.04 vol% CO2 conditions, respectively, as performance declines sharply with further increases. This adaptability underscores the versatility of the proposed method, paving the way for more efficient and practical CO2 capture technologies. © 2025 Elsevier B.V.

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