With kaolin-SiO2 as silicon source

lithium orthosilicate sorbents were prepared by impregnation- precipitation method. The crystal structures and morphologies were characterized by XRD and SEM

respectively. The CO2 absorption performance was studied by a thermogravimetric analyzer. The results indicated that the adsorbing capacity of kaolin-Li4SiO4 was higher than SiO2-Li4SiO4 at 350-700℃ in comparison with Li4SiO4 prepared with commercial SiO2. The high purity Li4SiO4 can be prepared by the impregnation-precipitation method successfully. The maximum adsorption of Li4SiO4 made by impregnation-precipitation method got up to 35.7% (mass) (704℃)

which was 5.9% (mass) higher than Li4SiO4 made by solid method. The CO2 chemisorption produced directly over the Li4SiO4 particles was the limiting step of the whole reaction process when the temperature was lower than 600℃. The CO2 chemisorption process controlled by diffusion process was the limiting step of the whole reaction process when the temperature was higher than 650℃. The lithium diffusion rate of samples made by impregnation-precipitation method was nearly double for samples made by solid method. The rate of CO2 chemisorption produced directly over the Li4SiO4 particles made by impregnation-precipitation method was higher.