Novel Na-silicates CO₂ sorbents from fly ash

Despite the very good CO₂ uptake of lithium based silicates at high temperature, this material is expensive and not very abundant. Therefore, there is the need to develop high temperature sorbents based on low-cost and widely available materials. In this work, Na-silicates prepared by mixing sodium carbonate with fly ash (FA) in the molar ratio of Na₂CO₃:SiO₂ of 1:1 and 4:1 were evaluated for their capacity to chemisorb CO₂ at 700°C. This temperature was chosen as it is compatible with post-combustion technologies. Pure Na-FA sorbent (NaCO₃:SiO₂ molar ratio of 1:1) was able to adsorb 1.8 mmol CO₂/g sorbent. The CO₂ uptake capacity increased to 2mmol CO₂/g sorbent in presence of 20% Li₂CO₃ as additive. Therefore, this work suggests that Na-silicate materials with acceptable CO₂ uptake can be developed as high temperature sorbents for post-combustion technologies.