The development of effective CaO-based CO₂ sorbents via a sacrificial templating technique

Abstract

A carbon-based sacrificial templating approach was employed to realize single-pot synthesis of cyclically stable CaO-based CO sorbents. The sacrificial carbonaceous template was formed through resorcinol-formaldehyde polymerization reaction. The resultant sorbents following the thermal decomposition of the carbonaceous template featured an inverse opal-like macrostructure composed of a highly porous nanostructured backbone. In addition to pure CaO, sorbents supported with AlO, MgO, YO, and ZrO were synthesized. SEM and XRD were utilized to characterize the morphology and the chemical composition of the synthetic CO sorbents, respectively. The cyclic CO uptake performance of the synthetic sorbents was assessed by TGA and compared to limestone. All of the synthetic sorbents exhibited an improved CO uptake performance when compared to limestone. The performance enhancement became more pronounced in the case of supported sorbents. The sorbent with the best CO uptake performance was supported by a mixture of AlO and YO, and exhibited a CO uptake of 0.61 g CO/g CaO after 10 cycles of calcination and carbonation under practically relevant operating temperatures, which exceeded the CO uptake of limestone by more than 350%.

Self-activated, nanostructured composite for improved CaL-CLC technology

“…9 shows the TEM images of the as-synthesized CaO/CuO matrix composites and CuO*, respectively. The CaO/CuO matrix composites synthesized by SCS were nanostructured with grain sizes below 200 nm, which is highly advantageous since this reduces the diffusion path lengths of CO 2 in the sorbent, leading in turn to high rates of CO 2 uptake [31]. This is mainly due to the formation of various gases during SCS process, which inhibits particle size growth and favours synthesis of nano-structure materials with high specific surface area [24,25].…”

CO2 Uptake and Cyclic Stability of MgO-Based CO2 Sorbents Promoted with Alkali Metal Nitrates and Their Eutectic Mixtures

“…Indeed, deactivation in the range of 30-60% of the initial uptake has been reported 23,33,34 . Previous studies have attributed the decay in the CO2 uptake of MgO largely to sintering, however without providing experimental evidence 23,27,28 , assuming instead an analogy to the behavior of CaO-based sorbents 10,11,37,38 . Only recently, Zhao et al 31 provided evidence that the surface area and pore size of a NaNO3-promoted mesoporous MgO sorbent decreased after carbonation and subsequent regeneration.…”

Optimization of the structural characteristics of CaO and its effective stabilization yield high-capacity CO2 sorbents

“…Yet, the majority of these works have fallen short of ensuring a structure that meets all of the essential characteristics outlined above. An additional concern is that some works that have reported an attractive CO 2 uptake, have tested the materials under unrealistic operating conditions (e.g., regeneration in pure N 2 at temperatures <900 °C) 36 , or are based on synthesis protocols that rely on environmentally harmful precursors 17 , 37 – 39 .…”