Experimental and modeling investigation on CO2 sorption kinetics over K2CO3-modified silica aerogels

K 2 CO 3 -modified silica aerogels (K 2 CO 3 /SG) were synthesized by the two-step sol-gel and wet impregnation method using K 2 CO 3 and tetraethoxysilane (TEOS) as starting materials and ethanol as solvent. CO 2 sorption behaviors of the sorbent were tested under ultra-dilute flue gas conditions of 20–60   °C, 1%CO 2 , 2%H 2 O and balanced N 2 with gas hourly space velocity (GHSV) of 4000   h −1 using a modified fixed-bed reactor. Experimental CO 2 uptakes of the sorbent under different temperatures were correlated to several kinetics models to study the kinetics performances. The effects of temperature, K 2 CO 3 loading, GHSV, H 2 O:CO 2 molar ratio and H 2 O pretreatment time on CO 2 sorption capacity and kinetics performances of the sorbent were further demonstrated. It is found that the two-step sol-gel and wet impregnation method could benefit the sorbent improved physical properties, superior surface characteristics and enhanced CO 2 sorption performances. Amongst various kinetics equations, the modified Avrami fractional kinetics model could well describe the CO 2 sorption process over K 2 CO 3 /SG. CO 2 sorption capacity decreases with the increase of temperature. With the increasing K 2 CO 3 loading, GHSV, H 2 O:CO 2 molar ratio and H 2 O pretreatment time, CO 2 sorption capacity increases first and then decreases. CO 2 sorption kinetics increases with the increasing temperature and H 2 O pretreatment time, while it decreases with the increasing K 2 CO 3 loading. CO 2 sorption kinetics keeps rather stable and then increases significantly with the increasing GHSV and H 2 O:CO 2 molar ratio.