Fabrication of Lithium Silicates As Highly Efficient High-Temperature CO2 Sorbents from SBA-15 Precursor

A series of lithium silicates with improved CO 2 sorption capacity were successfully synthesized using SBA-15 as the silicon precursor. The influence of Li/Si ratio, calcination temperature, and calcination duration on the chemical composition and CO 2 capture capacity of obtained lithium silicates was systematically investigated. The correlation between CO 2 sorption performance and crystalline phase abundance was determined using X-ray diffraction and a normalized reference intensity ratio method. Under the optimized condition, Li-SBA15-4 prepared using Li/Si = 4 that contains mainly Li 4 SiO 4 achieved an extremely high CO 2 capture capacity of 36.3 wt % (corresponding to 99% of the theoretical value of 36.7 wt % for Li 4 SiO 4 ), which is much higher than the Li 4 SiO 4 synthesized from conventional SiO 2 sources. It also showed very high cycling stability with only 1.0 wt % capacity loss after 15 cycles. Li-SBA15-10 (Li/Si = 10) that mainly contains Li 8 SiO 6 displayed an extremely high CO 2 uptake of 62.0 wt %, but its regeneration capacity was poor, with only 10.5 wt % of reversible CO 2 capture capacity. The influence of CO 2 concentration on the CO 2 capture performance of Li-SBA15-4 and Li-SBA15-10 samples was also studied. With the decrease in CO 2 concentration, relatively lower temperatures are needed for its maximum CO 2 capture capacity. The CO 2 sorption kinetics and mechanism for Li-SBA15-4 and Li-SBA15-10 samples were explored. Overall, we have shown that the lithium silicates synthesized from SBA-15 possessed much improved CO 2 sorption performance than that attained from conventional SiO 2 .