Na/K Binary Synergetic Effect in Lithium Orthosilicate for Enhancing High-Temperature CO2 Capture

Binary liquid doping of Na/K with various molar ratios into lithium orthosilicate (Li3.92NaxKySiO4) were synthesized by citric acid-assisted sol-gel methods. The CO2 sorption capacity of Li3.92NaxKySiO4 was investigated by TG analysis under a gas stream containing 50% CO2 and 50% N2 in a wide range from room temperature to 900 0C. Results indicated the sorption of CO2 for the different Na/K doping lithium orthosilicate occurred between 480-700 0C and the maximum sorption of CO2 was obtained at approximately 700 0C. The optimum ratio of binary doping of Na/K into lithium orthosilicate was determined to be 1:1 (Li3.92Na0.04K0.04SiO4) and the maximum sorption of CO2 may attain up to 30.7% (g/g) under the condition of optimum Na/K doping ratio, implying synergetic enhancement effect of Na and K elements on doping vacancies into the Li4SiO4 lattice may enhance the CO2 sorption capacity.