Evaluation of reaction kinetics of CO 2 and Li 4 SiO 4 by thermogravimetry under various CO 2 partial pressures

Abstract The CO 2 absorption kinetics of Li 4 SiO 4 , which attracted interest as CO 2 absorbent, under P (CO 2 ) of 1.0, 0.1 and 0.03 bar was evaluated using thermogravimetry at fixed temperatures between 460 °C and 600 °C. Reaction rate and saturated reaction ratio increased with increasing temperature and P (CO 2 ). Under P (CO 2 ) of 1.0 bar and 0.1 bar, reaction rate at initial period was enhanced by decreasing particle size and variation of reaction ratio by time could be successfully explained by using Jander model assuming Li + diffusion process induced by difference of CO 2 concentration as rate determining step. Under P (CO 2 ) of 0.03 bar, Jander model assuming superficial reaction between CO 2 gas and Li 4 SiO 4 solid surface as rate determining step was more applicable, indicating change of rate determining step varied from diffusion process to superficial one by decreasing P (CO 2 ) from 0.1 bar to 0.03 bar.