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

Highly efficient K2CO3-doped lithium orthosilicate (Li4SiO4) sorbents were synthesized using acid treatment to overcome the typical kinetic limitations of sorbents at low CO2 concentrations. The effects of K2CO3 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 K2CO3 greatly affected the physical-chemical properties and absorption kinetics of the sorbents. On one hand, K2CO3 formed a solid solution with Li4SiO4 and generated favorable characteristics (a smaller crystal size, corrugated morphology, larger surface area and higher surface concentration of Li2O), significantly facilitating the chemisorption processes. On the other hand, a higher amount of doped K2CO3 was located on the surface, which induced molten phases during CO2 absorption, remarkably decreasing the diffusion processes. Therefore, 0.1 M K2CO3 doped sorbent obtained noticeable absorption capacity and good regenerability in 15 vol.% CO2.