Template-assisted synthesis of CaO-based sorbent for carbon capture

DOI: 10.1038/s41467-018-04794-5

“Recently, template-assisted synthesis approaches have been adopted to realize hollow microspheres and nanospheres for a plethora of applications, including catalysis, energy storage, drug delivery etc.^40,41. These templates, being either hard (e.g., silica, carbon) or soft (e.g., micelles, emulsions), are coated via techniques that typically involve the precipitation of inorganic precursors onto their surface or the layer-by-layer assembly of inorganic particles^42,43. The final structure, obtained after the selective removal of the template via dissolution, etching or thermal decomposition, is composed of a hollow interior that is contained by an often mesoporous shell⁴⁴. To limit the complexity and to increase the throughput of the synthesis procedure, a favorable approach would involve the simultaneous formation of the template and the precipitation of the compound(s) of interest.”

“Herein, we report a facile, template-assisted synthesis approach to yield a highly effective, MgO-stabilized, CaO-based CO₂ sorbent that relies on environmentally benign precursors. The synthesis protocol adopted here features the aforementioned desirable one-pot characteristics. Carbonaceous spheres, formed in situ from a xylose precursor during hydrothermal synthesis, act hereby as a template and encapsulates compounds of Ca and Mg that are precipitated simultaneously via the hydrolysis of urea. Thermal removal of the template yields hollow microspheres with highly porous shells. The resultant structures contain all of the key features that are essential to yield a CaO-based sorbent with a high and cyclically stable CO₂ uptake. After 30 cycles of calcination and carbonation under “harsh” operating conditions, the CO₂ uptake of the materials synthesized is 0.50 g_CO2/g_sorbent (equivalent to a capacity retention of 83%), exceeding the capacity of the benchmark limestone by almost 500%.”