Post-combustion CO2 capture using supported K2CO3: Comparing physical mixing and incipient wetness impregnation preparation methods

Abstract

CO2 capture performance of 50wt.%K2CO3/alumina was investigated using various types of alumina supports such as γ-Alumina, Boehmite and Aerogel. Physical mixing and incipient wetness impregnation were used for preparing sorbents. Physically mixed K2CO3/γ-Alumina was the most efficient sorbent, with a maximum CO2 capture capacity of 5.5mmol CO2/g K2CO3. γ-Alumina displayed the lowest, and Aerogel the highest, hydrophilicity and surface area. Increasing hydrophilicity and surface area also increased water adsorption capacity, which adversely affected the CO2 capture capacity of the physically mixed sorbents. The excess water adsorption capacity converted K2CO3 to an almost inactive precursor of K2CO3·1·5H2O. BET and SEM results showed that recrystallization of K2CO3 from water had an adverse impact on the physical structure of the impregnated sorbents which affected their CO2 capture performance. The kinetic behavior of the samples was analyzed using the Avrami kinetic model. K2CO3/γ-Alumina prepared by physical mixing and impregnation methods showed the highest carbonation rates with K-values of 0.1168 and 0.2260, and n-values of 1.1257 and 1.2004, respectively. K2CO3/Aerogel and K2CO3/Boehmite prepared by the physical mixing method exhibited higher performance than the respective impregnated sorbents in terms of carbonation rate and CO2 capture capacity.