Colloidal Nanoclusters of MgO Coated with Alkali Metal Nitrates/Nitrites for Rapid, High Capacity CO₂ Capture at Moderate Temperature

Abstract

Colloidal nanoclusters of metal oxides constitute a promising new class of building blocks for a range of advanced functional materials. Herein, we report on the development of colloidal nanoclusters of MgO for CO2 capture prepared by a novel nonhydrolytic sol–gel reaction followed by the deposition of alkali metal salts by methanol evaporation-induced surface precipitation. The CO2 uptake exceeded 11.7 mmol g–1 (514.8 mg CO2 per 1 g of adsorbent) in 30 min in the presence of 100% dry CO2 under ambient pressure (1 bar) at 340 °C and reached 15.7 mmol g–1 (690.8 mg CO2 per 1 g of adsorbent) in 4 h. Colloidal nanoclusters possessing multiple inner grain boundaries and rough surfaces allowed for a dramatic increase in active surface area of MgO coated with thin layers of alkali metal salts and enabled the rapid conversion of MgO to MgCO3 with high conversion ratio. It was also discovered that the CO2 uptake loading and the regenerability of the sorbents can be enhanced on introduction of nitrite salts to the coating layer through the formation of magnesium nitro or nitrate species, which increased the critical thickness of product layers and mitigated the degradation of nanoclusters over the repeated sorption/desorption cycles.

Impact of organic interlayer anions on the CO 2 adsorption performance of Mg-Al layered double hydroxides derived mixed oxides

“…However, after coating with 15 mol% (Li-Na-K)NO 3 , the CO 2 uptake slightly increased when the Mg/Al ratio was 5:1 to 9:1, and significantly increased to 2.03 when the Mg/Al ratio was increased to 20:1. Similar results have also been observed by Harada et al [52,53] and Kim et al [51] .…”

“…It is well known that doping with alkali metal carbonates can further promote the LDHs derived CO 2 adsorbents [52] . However, recently Harada et al [52,53] developed (Li-Na-K)NO 3 molten salt coated MgO particles with enhanced CO 2 capture capacity. Kim et al [51] also reported an NaNO 3 promoted LDH with a Mg/Al ratio of 20 and achieved a high CO 2 capture capacity.…”

Mesoporous MgO promoted with NaNO3/NaNO2 for rapid and high-capacity CO2 capture at moderate temperatures

“…Commonly used strategies to improve the CO 2 capture capacity of MgO include enlarging the surface area [19][20][21][22], changing operation conditions [19,23,24], and incorporating promoters [25][26][27][28][29]. Among these strategies, the use of appropriate promoters has been proved to be most effective so far.…”

Nanoparticle Clusters: Assembly and Control Over Internal Order, Current Capabilities, and Future Potential

“…The large active cluster surface area has also been exploited in CO 2 -capture experiments, using clusters formed from MgO NPs. [137] The rapid conversion of MgO to MgCO 3 was reversible, and was further enhanced by coating of the clusters with alkalimetal nitrate salts, opening a potential pathway for flexible CO 2 storage.…”