Absorption behaviors study on doped Li4SiO4 under a humidified atmosphere with low CO2 concentration

• Pure Li4SiO4 sorbent exhibits low capacity at low CO2 concentrations.
• K-doped Li4SiO4 exhibits much higher absorption capacity.
• The best sorbent can be achieved by maximized KLi(CO3) and minimum Li2SiO3.
• The optimized sorbent have good stability.

Potassium carbonate was used as a doping agent to improve the absorption properties of Li4SiO4 for CO2 capture during critical sorption-enhanced steam methane reforming (SESMR) under moderate temperature and low CO2 concentration with moisture.The mechanism of CO2 absorption onto pure and K-doped Li4SiO4 under various CO2 concentrations was experimentally and theoretically studied. At 575 °C, pure Li4SiO4 exhibited poor CO2 absorption capacity because of low CO2 diffusion through the solid Li2CO3 shell of the sorbent. By contrast, the K-doped Li4SiO4 sorbent showed excellent performance. K2CO3 and Li2CO3 can form eutectic compounds that facilitate the diffusion of CO2 into the sorbent crystals and enhance the absorption of CO2. The amount of doping agent was further optimized under different operating conditions and numerical analysis. Absorption–desorption cycles were performed under industrial operating conditions and the optimized K-doped Li4SiO4 exhibited satisfactory absorption capacity and stability.