Particle size dependence of CO₂ absorption rate of powdered Li₄SiO₄ with different particle size

Abstract

Particle size dependence of CO₂ absorption rate of powdered Li₄SiO₄ with four kinds of particle sizes was studied by SEM observation, particle size distribution measurement, and thermogravimetry. Average particle sizes of the powdered single phase Li₄SiO₄ samples were estimated about 26 μm, 34 μm, 53 μm, 70 μm, respectively by the particle size distribution measurement and SEM observation. The measurement of apparent rate constant k for the CO₂ absorption reaction showed that k values of all the powdered Li₄SiO₄ samples increase with the increasing measurement temperature T, following the Arrhenius equation in the region of 620-660°C, while the k values abruptly increase deviating the Arrhenius equation over 670°C. It was also noted that the k values seem to depend on the particle size of the powdered Li₄SiO₄ samples, that is, the k values increase with the decreasing particle size. Moreover, difference between the k values of all the powdered samples at same temperature was found small in the region of 620-660°C, while the difference was found large over 670°C. For Li₄SiO₄ with smaller particle size, Δk = k_700°C - k_660°C was found larger, vice versa, the Δk was found smaller for Li₄SiO₄ with larger particle size. The values seem to correspond with reaction mechanism for CO₂ absorption of Li₄SiO₄ particle.