In situ- synchrotron X-ray diffraction on the synthesis and CO 2 capture of Li 8 SiO 6

F. COVA; G. AMICA; M. V. BLANCO

Thessaloniki

Congreso; Euromat 2017; 2017

The emission of greenhouse gases resulting from industrial and energy sources has been identified as one of the major causes of anthropogenic global warming. Because of this, the technology of CO2 capture and storage (CCS) has been recognized as a promising approach to diminish the current releases of CO2 while the energy matrix moves towards clean and renewable energy sources. Among the materials capable of capture and store CO 2 , lithium silicates have shown large CO2 sorption capacity within the temperature range from 400 °C to 650 °C. Recently, it has been reported that Li 8 SiO 6 can chemisorb significant quantities of CO 2 at temperatures equal or higher than 600 °C (11.9 mmol of CO 2 per gram at 650 °C. In this work we study the synthesis and the phases involved in the CO2 capture of lithium oxosilicate (Li8SiO6) using synchrotron X-ray diffraction. Three samples containing Li 8 SiO 6 were synthesized via a solid-state reaction using Li 2 O and SiO 2 as starting materials. Two of them were mechanically milled before the synthesis, while the third one was only mixed. The samples were placed in quartz capillaries and then heated with a temperature ramp of 5 °C.min -1 from room temperature to 770 °C. The synthesis was followed by in situ synchrotron X-ray diffraction using a 2 D detector, at a wavelength of 0.1771 A. According to the results, the formation of Li 8 SiO 6 starts at 500 °C and the sample whose reactants were mixed before heating exhibited a higher purity compared to the milled ones. The CO2 chemisorption of the different samples was evaluated from 50 °C to 770 °C by in situ X-ray diffraction. The identification of intermediate and final phases during the reaction with CO 2 (Li4SiO4, Li2SiO3 and Li2CO3) allowed to gain insight in the reaction mechanism of Li8SiO6 with CO2.