CO2 Absorption/Release Properties of Lithium Silicate (Li2SiO3) Powders Prepared by the Sol-Gel Process

Abstract

The sol-gel synthesized powder was a single phase Li2SiO3. This synthesized powder was reacted with CO2at temperatures ranging from the ambient temperature to 511 K, and the products can reverted reversibly to Li2SiO3above 511 K. The degree of absorption was defined as the value obtained by dividing the fractional mass gain of Li2SiO3after absorption by the fractional mass gain corresponding to a 100% reaction. Consequently, the degrees of absorption of the sol-gel synthesized powders were determined to be 9.6%, 13.9%, 16.1% and 20.4% under the absorption condition at 313 K, 333 K, 353 K and 373 K for an exposure time of 115.2 ks, respectively. The specific surface area of synthesized powder was measured as 40 m2/g, higher than that of Li2SiO3synthesized by solid state reaction of 30 m2/g. After CO2absorption, the specific surface area of synthesized Li2SiO3was increased with the increase of absorption degree because of the volume expansion. Compared with Li2SiO3synthesized by solid state reaction, Li2SiO3powder synthesized by sol-gel process possessed bigger specific surface areas and higher micro pore volumes. Through the measurement of FE-SEM and BET, the average diameter of micro pores was decreased after CO2absorption, because of the generation of Li2CO3. The absorption behavior could be best explained by an intraparticle diffusion mechanism, that is, the diffusion of CO2gas through the reaction product with an apparent activation energy of 28 kJ∙mol-1was a rate-determining step of the absorption reaction.