CO capture by LiCaSiO and enhancement with alkali carbonates

• Published in: Physical chemistry chemical physics : PCCP 2023-08, Vol.25 (33), p.21944-21956
• Main Authors: Wang, Zhen, Sun, Chenteng, Xu, Qian, Zou, Xingli, Cheng, Hongwei, Lu, Xionggang
• Format: Article
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d3cp02338a

Alkali and alkali earth oxides show good CO 2 capture performance for carbonation, while their regeneration occurs at high temperatures, leading to a high energy penalty. When alkali oxides and alkali earth oxides combine with SiO 2 to form oxysalts, the regeneration temperatures can be reduced, and the CO 2 adsorption capacity is maintained. In this study, the reaction between CO 2 and Li 2 CaSiO 4 , composed of stoichiometric CaO, Li 2 O, and SiO 2 , was evaluated thermodynamically by DFT. The synthesized Li 2 CaSiO 4 with and without alkali carbonates was used as CO 2 sorbents, and their CO 2 adsorption performances were examined using thermal analyses. The phase and morphology of Li 2 CaSiO 4 before and after CO 2 adsorption were characterized by XRD and SEM. According to the thermodynamic evaluation and the XRD results, Li 2 CaSiO 4 could adsorb CO 2 and form CaCO 3 and Li 2 SiO 3 . The thermal analyses showed that the regeneration of Li 2 CaSiO 4 started from 575 °C, at which it was difficult to realize the CO 2 diffusion through the solid CaCO 3 product layer. The mixed alkali carbonates can improve the kinetics and facilitate the CO 2 adsorption of Li 2 CaSiO 4 . Alkali carbonates were effective in reducing the activation energy of the reaction and CO 2 diffusion at low temperatures and improving the cyclic stability because of the dispersing carbonation products. Cyclic stability of P-Li 2 Ca (a), 10(LiNa)Li 2 Ca (b), and 10(LiNaK)Li 2 Ca (c) (carbonation: 550 °C, two hours, 80% CO 2 ; regeneration: 590 °C, one hour, 100% N 2 ).