Understanding the competition between carbonation and sulfation of Li4SiO4-based sorbents for high-temperature CO2 capture

High-temperature CO2 adsorption is an important method in reducing the excessive CO2 emissions for the mitigation of global climate change. As a potential high-temperature CO2 sorbent, Li4SiO4 attracted extensive concern due to its high CO2 capacity with excellent stability. However, gas impurities in industrial flue gas, especially SO2 affect the CO2 adsorption process, and the competition between SO2 and CO2 during the adsorption process by Li4SiO4 is lack of understanding. This work studied the competitive behavior between carbonation and sulfation through experimental tests, characterizations, and DFT calculations. Results show that carbonation can slightly inhibit the proceeding of sulfation while sulfation almost prevents the occurrence of carbonation for both Li4SiO4 and K-Li4SiO4. In addition, the doping of K2CO3 in Li4SiO4 is observed to significantly promote both the carbonation and sulfation process. Furthermore, stable adsorption structures of CO2 and SO2 on Li4SiO4 were obtained via DFT calculation, which verifies the mutual inhibition between carbonation and sulfation. These results provide a well understanding of the competition between carbonation and sulfation of Li4SiO4-based sorbents, and are helpful for the design and optimization of CO2 adsorption process.