Carbon dioxide absorption behavior of surface-modified lithium orthosilicate/potassium carbonate prepared by ball milling. (2nd November 2016)

• Record Type: Journal Article
• Authors: Kanki, Kyohei; Maki, Hideshi; Mizuhata, Minoru
• Is Part Of: International journal of hydrogen energy. Volume 41:Number 41(2016)
• Page Start: 18893
• Page End: 18899
• Publication Date: 2016-11-02
• Subjects: CO2 chemisorption -- Ball milling -- Molten salt -- Lithium ceramic -- Thermal analysis; Hydrogen as fuel -- Periodicals; Hydrogène (Combustible) -- Périodiques; Hydrogen as fuel; Periodicals; 665.81
• DOI: 10.1016/j.ijhydene.2016.06.158
• Languages: English
• ISSNs: 0360-3199

Abstract

Abstract: Lithium orthosilicate (Li4 SiO4 ) is a ceramic CO2 absorbent with a large absorptive capacity (36.7 wt.%) and heat resistance properties. Li4 SiO4 has applications as a separator in molten carbonate fuel cells, and as a direct CO2 absorbent in large-scale emission sources such as thermal power stations. The absorption and desorption reaction equilibrium temperature of Li4 SiO4 is around 993 K. This study investigates the CO2 absorption behavior of Li4 SiO4 at lower temperatures. Samples whose surfaces were modified with ball milling under an Ar atmosphere exhibited increased Brunauer–Emmett–Teller surface areas. Electron spin resonance (ESR) spectroscopy indicated an increase in the content of Si dangling bonds upon ball milling. Thermogravimetric-differential thermal analysis indicated two different CO2 absorption processes: chemisorption at the Li4 SiO4 surface at temperatures below 773 K; bulk diffusion at temperatures above 773 K. Isothermal analysis indicated that ball milling and adding K2 CO3 decreased the activation free energy. Graphical abstract: Highlights: CO2 absorption behaviors of Li4 SiO4 at lower temperatures were researched. Effect of surface modification of silicate on CO2 storage phenomena was discussed. Two absorption CO2 processes of the ball-milled Li4 SiO4 samples were observed. Gibbs free activation energy was decreased by the ball milling.