CO₂ Capture by As-Synthesized Amine-Functionalized MCM-41 Prepared through Direct Synthesis under Basic Condition

The as-synthesized amine-functionalized MCM-41 material was prepared through direct synthesis by co-condensation of tetraethyl orthosilicate (TEOS) with 3-aminopropyl triethoxysilane (APS) at different molar ratios and a pH of approximately 13 for CO₂ capture under various CO₂ concentrations, temperatures, and moistures. The prepared as-synthesized APS-functionalized MCM-41 (as-APS/MCM) possessed nitrogen content up to 3.46 mmol N/g and CO₂ adsorption capacities up to 1.18 mmol/g under 15% CO₂ in N₂ at 35 °C and 1.74 mmol/g under pure CO₂ at 25 °C. The CO₂ adsorption capacity was 73% higher than the APS-grafted calcined MCM-41 prepared by postmodification. Because the CO₂ adsorption capacity of the as-APS/MCM was found to come mainly from the coated APS rather than the incorporated APS, prehydrolysis of TEOS and post-treatment including template removal and APS neutralization were not required. Dynamic adsorption–desorption cycles revealed that the as-APS/MCM possessed high thermal stability for CO₂ capture

One-Pot Synthesis and Pelletizing of Polyethylenimine-Containing Mesoporous Silica Powders for CO₂ Capture

Polyethylenimine-containing mesoporous silica powders (PEI-MSP) were prepared through one-pot synthesis from mixtures of tetraethyl orthosilicate and PEI in water/methanol. This proposed route required only 4% of reaction time and energy and used 50% of chemical reagents used in two-step synthesis of PEI-loaded SBA-15 (PEI/SBA) prepared through impregnation, thereby decreasing the cost of the resulting adsorbents. The PEI component in the one-pot route functioned not only to provide amine active sites for CO₂ capture but also as a basic catalyst and a pore-structure-directing agent. The pelletized PEI-MSP using our proposed binder solution possessed high mechanical strength, durability, and CO₂ adsorption capacity and recovery, satisfying industrial requirements and reducing the pressure drop in practical use. Dynamic adsorption–desorption cycles of PEI-MSP powders and pellets revealed high thermal stabilities. Therefore, this one-pot synthetic route is promising for preparing PEI-MSP as appropriate adsorbents for CO₂ capture when using a temperature swing adsorption technology