CO2 Adsorption Ability and Thermal Stability of Amines Supported on Mesoporous Silica SBA-15 and Fumed Silica

In this study, monoamine 3‐aminopropyl silane (APS) grafted on silica supports were prepared either by post‐modification of mesoporous template‐free SBA‐15 and nonporous fumed silica with 3‐aminopropyl triethoxysilane (APTES) or by direct synthesis using a reaction mixture of APTES, TEOS and organic template P123. The CO2 adsorption capacities and efficiencies of amine (defined as CO2/N ratio) on APS grafted silica adsorbents as well as the thermal stability of grafted APS were analyzed and further compared with those of multiamine, tetraethylenepentamine (TEPA), loaded on mesoporous SBA‐15 and nonporous fumed silica. The TEPA‐loaded silica adsorbents exhibited higher CO2 adsorption capacities but lower thermal stability than the APS‐grafted silica adsorbents. The low cost and commercially available nonporous fumed silica was found to be an appropriate support for amine loading. The TEPA‐loaded fumed silica possessed a CO2 adsorption capacity of 3.97 mmole CO2/(g of adsorbent) and a CO2/N mole ratio of 0.37 under a 15% CO2/N2 mixed gas flow at 75 °C and 1 atm, which were higher than those of the TEPA‐loaded SBA‐15 due to the less CO2 diffusion hindrance. Besides, a high stability of TEPA on fumed silica in cyclic adsorption‐desorption of CO2 over the TEPA loaded on SBA‐15 was observed as well. Fumed silica is a useful support for amines on CO2 capture. The amine efficiency (CO2/N) of APS grafted on fumed silica reaches to 0.5. TEPA loaded on fumed silica possesses high stability and efficiency for CO2 capture. The order of thermal stability of amines on silicas is C3H6NH3+>C3H6NH2>TEPA. The stability of amines depends on their interaction to supports.