Potassium Silicate as Low-Temperature Binder in 3D-Printed Porous Structures for CO₂ Separation

Activated carbon sorbents were directly 3D-printed into highly adaptable monolithic/multi-channel systems by using potassium silicate as a low-temperature binder. By employing emerging 3D-printing technologies, monolithic structured sorbents were printed and fully characterized using N₂, Ar, and CO₂-sorption and Hg-intrusion porosimetry. The CO₂-capture performance and the required temperature for active-site regeneration were evaluated by thermogravimetric analysis-looping experiments. A mechanically stable activated carbon sorbent was developed with an increased carbon capture performance, even when a room-temperature regeneration by N₂ purging was applied. Although the CO₂ uptake slightly dropped after several cycles due to incomplete recovery at room temperature, a capacity increase of 25% was observed in comparison with the original activated carbon powder. To improve the recovery of the active sorbent, an optimization of the desorption step was performed by increasing the regeneration temperature up to 150 °C. This resulted in a CO₂ uptake of the composite material of 0.76 mmol/g, almost tripling the working capacity of the original activated carbon powder (0.28 mmol/g). An in situ X-ray diffraction study was carried out to confirm the proposed sorption mechanism, indicating the presence of potassium bicarbonates and confirming the combination of physisorption and chemisorption in our composites. Finally, the structured adsorbent was heated homogeneously by applying a current through the monolith. These results describe the development of a new type of 3D-printed regenerable CO₂ sorbents by using potassium silicate as a low-temperature binder, providing high mechanical strength, good chemical and thermal stability, and improving the total CO₂ capacity. Moreover, the developed monolith is showing a homogeneous resistivity, leading to uniform Joule heating of the CO₂ adsorbent.