Chemical Engineering Journal, Vol.356, 81-90, 2019
CO2 absorption property of Li4SiO4 in the presence of water vapor at room temperature
Lithium orthosilicate (Li4SiO4) powders were synthesized by heating a mixture of LiNO3 and amorphous SiO2 at 800 degrees C for 5 h in air. The formed powders were applied to capture CO2 in the presence of water vapor at room temperature (RT). Thermogravimetric (TG) analysis showed that the CO2 absorption reaction of Li4SiO4 was promoted even at RT as the relative humidity increased, whereas little absorption occurred under a dry CO2 flow. X-ray diffraction measurements, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy clarified that an amorphous phase and Li2CO3 were produced on the Li4SiO4 surface after the CO2 reaction in the presence of water vapor. The adsorption of water vapor resulted in the formation of a basic solution on the surface of Li4SiO4 particles. This solution promoted CO2 absorption to Li4SiO4 even at RT. As a result, the CO2 absorption capacity of Li4SiO4 in the presence of water vapor at RT was greater than that of Li4SiO4 in the presence of dry CO2. Gas chromatography and TG revealed that the Li4SiO4 absorbed CO2 in the presence of water vapor and released CO2 over two temperature regions, namely a region below 500 degrees C and one above 600 degrees C. The single phase of Li4SiO4 was regenerated by heating the CO2-absorbed Li4SiO4 at 700 degrees C.