Effect of Na-doping on CO2 absorption of Li4SiO4

Sodium-doped lithium silicate as CO2 absorbent at 500C to 750C 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 arrived at (46 0.6)%(w) in CO2 atmosphere at 700 degrees C within 15 min. Moreover, the CO2 concentration in gas phase influenced the rate of CO2 absorption.