High temperature capture of low concentration CO2 by Na/Ca-doped lithium orthosilicate with KIT-6 as precursor

Using KIT-6 as the silica source, a series of Li 4 SiO 4 adsorbents (KIT-6-Li 4 SiO 4 ) were synthesized by impregnation precipitation method for high temperature CO 2 capture. Then, the KIT-6-Li 4 SiO 4 -800–4 (KL-800–4) material, was selected to analyze the improvement of the adsorption performance by Ca 2+ /Na + eutectic doping modification. These adsorbents were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and low temperature N 2 adsorption/desorption, and the CO 2 adsorption capacity of them was explored. At 600 °C and under 15 vol% CO 2 , KL-Ca0.03 and KL-Na0.06 sorbents resulted in a CO 2 uptake of 29.17 wt% and 35.35 wt% (close to the theoretical maximum), respectively，which are much higher than that of KL-800–4 (14.73 wt%). After 10 adsorption/desorption cycles, the adsorption capacity of KL-Na0.06 increased by 1.35 wt%. We found that KL-Na0.06 has more advantages compared with traditional lithium orthosilicate and undoped adsorbents, including lower energy consumption, higher CO 2 adsorption capacity and better cycling ability. Finally, the double exponential model had a high degree of fit for the adsorption of CO 2 by Li 4 SiO 4 .