Effect of Sodium Ortho and Pyrosilicates (Na4SiO4-Na6Si2O7) Mixture during the CO2 Chemical Capture Performance

A novel CO2 sorbent composed of sodium orthosilicate (Na4SiO4), sodium pyrosilicate (Na6Si2O4), and sodium carbonate (Na2CO3) was successfully synthesized through the solid-state method. This sorbent was evaluated as CO2 captor (theoretical capture capacity of 4.08 mmol of CO2 per gram of material) under CO2-saturated and partial pressure conditions, using dynamic and isothermal approaches. Results evidenced that the sorbent was sensitive to the CO2 partial pressure, although significant CO2 capture efficiencies were observed between 100 and 830 degrees C, at any CO2 partial pressure. The characterization of the isothermal products showed a complex CO2 chemisorption process, where sodium metasilicate (Na2SiO3), produced as the secondary phase, participated in the CO2 capture in the low temperature range, while the initial presence and in situ generation of Na6Si2O7 played an important role during the whole process. The positive effect of Na6Si2O7 was confirmed through the synthesis and evaluation of a pyrosilicate-based sorbent. Kinetic analysis was performed showing comparable and favorable results in comparison to previous studies using alkaline ceramics for CO2 capture. Furthermore, the sorbent was able to cycle 10 times, at least, maintaining an efficiency of similar to 70%. Hence, the combination of Na4SiO4-Na6Si2O7 leads to high CO2 capture in a wide temperature range.

Automated summary

A novel CO2 sorbent composed of sodium orthosilicate, sodium pyrosilicate, and sodium carbonate was successfully synthesized and evaluated for CO2 capture. The sorbent showed sensitivity to CO2 partial pressure and exhibited high capture efficiency in a wide temperature range. Additionally, it demonstrated good cycling stability with maintained capture efficiency.