3D-printed activated carbon monoliths for efficient CO₂ capture

In gas-phase adsorption processes, adsorbents are typically used as beads or pellets in a fixed bed. While these shapes permit their application in adsorption processes, they fall short of achieving optimal performance. This limitation can be greatly improved by employing structured materials, which offer reduced pressure drop and enhanced mass and energy transfer, thereby improving the overall process efficiency. Herein, resol-based activated carbons (ACs) are structured using 3D-printed sacrificial water-soluble templates to produce custom-designed monoliths for efficient carbon dioxide (CO2) capture. The influence of activation conditions (time under CO2 flow) on textural properties, CO2 adsorption capacity, and CO2/nitrogen (N2) selectivity are investigated. Prolonging the activation time leads to a progressive increase in surface area and micropore volume, as more carbon is removed through gasification reactions with CO2. The resulting enhancement in porosity improves the CO2 adsorption capacity. However, the AC with the lowest burn-off has the highest selectivity for CO2 over N2 (considering a binary CO2/N2 mixture with 15 mol% of CO2) due to its lower ability to adsorb N2. Overall, this work highlights the potential of a modern 3D-printing fused deposition modeling technique to engineer structured adsorbents with applications in gas separation processes, such as CO2 capture.