Influence of impregnation and calcination conditions on K2CO3 sorbents for CO2 capture

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

“Impregnation and calcination parameters are important factors that need to be considered when the wet impregnation method was employed for preparing potassium-based adsorbents. Chalermsinsuwan et al. prepared the K₂CO₃/γ-Al₂O₃ adsorbent using the wet impregnation method and they reported that the structure and basicity of the adsorbent depended on several factors including basic solution (NaOH, Ca(OH)₂, and Na₂CO₃), basicity (pH=8∼12) and shaking time (12-24 h). NaOH solution with a high pH as solvent for K₂CO₃ impregnation would benefit the adsorbent uniform K₂CO₃ dispersion and smaller grain size, and the desired adsorbent exhibited a high CO₂ uptake of 4.34 mmol CO₂/g (Charoenchaipet et al., 2020). Esmaili et al. reported that increasing the initial solution concentration and extending the impregnation time could promote the carbonation capacity of K₂CO₃/Al₂O₃, while its CO₂ adsorption capacity increased first and then decreased with the elevating calcination temperature and prolonging time. The desired adsorbent prepared under optimized parameters showed a high carbonation capacity of 1.75 mmol CO₂/g (Esmaili and Ehsani, 2013). The structure-performance relationships of potassium-based adsorbents also relied on the calcination temperature and atmosphere. Lee et al. reported that the increase in calcination temperature from 300°C to 700°C adversely affected the CO₂ adsorption capacity of K₂CO₃/TiO₂ calcined under N₂ and air atmospheres. This was due to the formation of K₂Ti₂O₅, K₂Ti₆O₁₃ and K₂Ti₄O₉ phases at higher calcination temperatures. Compared to the air atmosphere, inert N₂ stream could be more suitable for adsorbent preparation (Lee et al., 2010). Obvious decline in CO₂ uptake had been observed for K₂CO₃/SiO₂ calcined at high temperatures, due to the formation of inactive K₂Si₂O₅ and K₂Si₄O₉ (Cho et al., 2019). Hence, the calcination temperature should be carefully considered to alleviate the interactions between K₂CO₃ and metal oxides supports.”