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.
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