Molten K2CO3-promoted high-performance Li4SiO4 sorbents at low CO2 concentrations

Highly efficient K 2 CO 3 -doped lithium orthosilicate (Li 4 SiO 4 ) sorbents were synthesized using acid treatment to overcome the typical kinetic limitations of sorbents at low CO 2 concentrations. The effects of K 2 CO 3 on the structure and absorption properties were characterized using various morphological characterization techniques, differential scanning calorimetry (DSC) and thermogravimetric analysis (dynamic and isothermal). The results showed that different amounts of K 2 CO 3 greatly affected the physical-chemical properties and absorption kinetics of the sorbents. On one hand, K 2 CO 3 formed a solid solution with Li 4 SiO 4 and generated favorable characteristics (a smaller crystal size, corrugated morphology, larger surface area and higher surface concentration of Li 2 O), significantly facilitating the chemisorption processes. On the other hand, a higher amount of doped K 2 CO 3 was located on the surface, which induced molten phases during CO 2 absorption, remarkably decreasing the diffusion processes. Therefore, 0.1   M K 2 CO 3 doped sorbent obtained noticeable absorption capacity and good regenerability in 15   vol.% CO 2 .