Mesoporous Al2O3 materials as the support for K2CO3

https://doi.org/10.1016/j.ccst.2021.100011

“Mesoporous Al₂O₃ has been widely utilized for supporting K₂CO₃ as solid CO₂ adsorbents. The broad pore size distribution, especially the enriched mesoporous and macroporous structures, enable more K₂CO₃ being accommodated in Al₂O₃. Moreover, its high surface area offers opportunities for the uniform dispersion of K₂CO₃ on the support. CO₂ adsorption capacities of the Al₂O₃-supported K₂CO₃ adsorbents ranged from 1.45 to 2.88 mmol CO₂/g. The loss-in-capacity of the adsorbents over repeated cycles fluctuated remarkably in the 6.1-62.4% range (Bararpour et al., 2019; Cho et al., 2018; Durán-Guevara et al., 2015; Esmaili and Ehsani, 2014; Lee et al., 2014a; Lee et al., 2006a; Lee et al., 2011b; Qin et al., 2014; Zhao et al., 2009b). Physicochemical properties and carbonation capacities of the Al₂O₃-supported adsorbents depended on the alumina phases. Lee et al. identified the phase change of the alumina precipitate derived from Al(NO₃)₃•9H₂O and NaOH (Lee et al., 2014a). As calcination temperature increased in the 300-1200°C range, the alumina precipitate decomposed to form various phases: γ-AlOOH (300°C)→γ-Al₂O₃ (600°C)→δ-Al₂O₃ (950°C)→α-Al₂O₃ (1200°C). The deactivation issue of K₂CO₃/Al₂O₃ in repeated cycles could be well addressed by employing α-Al₂O₃ as support, while δ-Al₂O₃ support was conducive to improving regeneration capacities (Lee et al., 2014a). A novel alumina-aerogel support with an extraordinarily high BET surface area of 2019 m²/g was prepared, which enabled 50 wt.% K₂CO₃ being loaded for highly efficient CO₂ capture (2.88 mmol CO₂/g) (Bararpour et al., 2019).”