Preparation and characterisation of amino-functionalized pore-expanded mesoporous silica for carbon dioxide capture

In this study, the preparation of some large-pore ordered mesoporous silicas using a proper surfactant with different swelling agents was carried out. The synthesis of conventional SBA-15 was modified to obtain pore-expanded materials, with pore diameters up to 10 nm. To use a micelle swelling agent with a moderate swelling ability, three swelling agents were selected: 1-phenyl-decane (Dec), butyl benzene (BB), and mesitylene (Mes). These syntheses aimed to achieve a pore diameter enlargement but at the same time to avoid the formation of heterogeneous and/or poorly defined nanostructure of silica. The CO2 adsorbents were obtained by post-synthesis functionalization treatments carried out by grafting with 3-aminopropyl triethoxysilane. The CO2 adsorption/desorption experiments showed that carbon dioxide sorption capacities depend on the textural characteristics and the temperature used for the adsorption process. Good CO2 adsorption capacities were obtained for all prepared adsorbents, especially for SSBA-15-Mes-sil and SSBA-15-BB-sil samples. At 50 °C, the SSBA-15-Mes-sil sample has an adsorption capacity of 3.58 mmol CO2/g SiO2, and an efficiency of amino groups of 0.99 mmol CO2/mmol NH2. The results of adsorption capacities are comparable or even superior with the ones reported in literature for mesoporous silica functionalized with different amines. After nine adsorption–desorption cycles, the performance of the SSBA-15-Mes-sil adsorbent is relatively stable, with a low decrease in the adsorption capacity (0.1 mmol/g of CO2, i.e., 2.8% of initial capacity). These studies show the potential of mesoporous silica for carbon dioxide capture.