CO2 sorption kinetic study and modeling on doped-Li4SiO4 under different temperatures and CO2 partial pressures

Abstract The present study investigated the CO2 sorption mechanism on lithium orthosilicate (Li4SiO4) doped with potassium carbonate (K2CO3) in form of powders and macroporous pellets. The CO2 sorption performance was studied under different temperatures (540–580 °C) and CO2 partial pressures (0.04–0.50 atm). The results showed that the addition of K2CO3 improved the CO2 uptake rate and capacity, mainly at low-moderate CO2 partial pressures, owing to an increase of diffusion rate through the product layer. Moreover, a modified shrinking core model was developed to explain the mechanisms that occur during the sorption introducing a CO2 diffusion coefficient through the product layer depending on the Li4SiO4 conversion. The results showed an excellent fitting of the modified shrinking core model to the experimental data obtained in the tested sorption temperature and CO2 partial pressure range, both for the sorbent in powder and pellet form. Thus, the proposed model could be employed to well simulate the CO2 sorption kinetic behavior on K2CO3 doped Li4SiO4-based sorbents.