Abstract: Sodium-doped lithium silicate as CO2 absorbent at 500 ℃ to 750 ℃ 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 CO2-absorption 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 arrives at (46±0.6)%(w) in CO2 atmosphere at 700 ℃ within 15 min. Moreover, the CO2 concentration in gas phase influences the rate of CO2 absorption.

Key words: Lithium silicate, Absorption, Carbon dioxide, Doping, TG