Adsorption of CO2 on silica dioxide catalyst impregnated with various alkylamine

Silica dioxide catalyst (SiO2) can be modified by impregnating amine-containing compounds to improve the CO2 adsorption capacity. Four type of amines, i.e., monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA) and octadecylamine (ODA) were supported on silica dioxide particles. The amine-modified samples were characterized using FTIR, BET and FESEM. All the prepared solid sorbents exhibited type IV isotherm with hysteresis loop. Specific surface areas of the sorbents were significantly reduced due to blocking of micropores and mesopores by the amine compounds. Reactivity of solid sorbents towards CO2 was evaluated using isothermal CO2 adsorption by BET. CO2 adsorption capacity increased with the weight percent of amine compounds loaded onto the SiO2. 15 and 25 wt % MEA/SiO2 and 25 wt % ODA/SiO2 sorbents showed greater CO2 adsorption capacities compared to the virgin sample (SiO2). This study shows that the order of adsorption capacity for the four types of amines was MEA (4.05 wt % CO2/adsorbent) > ODA (2.45 wt % CO2/adsorbent) > DEA (1.71 wt % CO2/adsorbent) > TEA (0.91 wt % CO2/adsorbent). CO2 uptakes by ODA/SiO2 sorbents were higher than DEA/SiO2 and TEA/SiO2 is mainly due to their smaller pore volume and pore width of the adsorbent, therefore, greater interactions of CO2-ODA in pores. MEA/SiO2 has the highest ability in capturing CO2 because of the increasing steric hindrance of long chain ODA and alkyl substituent on DEA and TEA.