Effect of Na-doping on CO₂ absorption of Li₄SiO ₄

Sodium-doped lithium silicate as CO₂ absorbent at 500 °C to 750 °C was prepared by high-temperature solid-state reaction. The influence of sodium doping on the crystal structure of the absorbent was studied by X-ray diffraction (XRD). The microscopic morphologies of the absorbents were observed by scanning electron microscopy (SEM). The COrabsorption capacities were measured by a thermogravimetric analyzer, which showed that sodium doping could improve the CO₂-absorption ability of lithium silicate. It was found that the absorbent possessed the best performance when n(SiO₂): n(Li₂CO₃):n(Na₂CO₃)=1: 1.96:0.04. The maximum amount of CO₂ absorption arrived at (46± 0.6)%(w) in CO₂ atmosphere at 700 °C within 15 min. Moreover, the CO ₂ concentration in gas phase influenced the rate of CO₂ absorption.