Studying the Performance and Stability Characteristics of Triamine-Modified Mesoporous Silica Materials for CO2 Capture from Ambient Air (Student Poster #19)

Abstract Description: The concentration of CO2, the primary anthropogenic greenhouse gas driving global warming and climate change, has rapidly risen since the Industrial Revolution. In 2024, the global average CO2 concentration reached 425 parts per million by volume (ppmv), compared to 315 ppmv in 1958. This surge in emissions has led to an almost 2-degree Fahrenheit increase in global temperatures since the pre-industrial era. Direct air capture (DAC) of CO2 from the atmosphere offers a potential solution to this issue. Recognizing its importance, the U.S. Department of Energy has identified DAC as a key strategy for achieving net-zero emissions by 2050. In recent years, DAC technologies, including the cyclic adsorption-desorption of CO2 using amine-modified silica materials (commonly referred to as “aminosilica”) have gained significant attention. These systems hold promise for commercialization and could play a crucial role in mitigating climate change. To this end, this project focuses on developing optimized materials for DAC applications. Specifically, it explores the synthesis of triamine-grafted silica adsorbents. Triaminosilane, containing two secondary and one primary amine, was selected owing to its strong CO2 affinity. CARiACT G-10 silica (Fuji Silysia Chemical Ltd.) was used as the support material due to its low cost, high pore volume (1.2 cm³/g), large surface area (300 m²/g), small particle size (5 µm), and wide pores (20 nm). These properties enable high amine loading and CO2 uptake with nimble adsorption kinetics. A series of unique materials were synthesized via grafting, with variations in water and triamine quantities. Thermogravimetric analysis (TGA) was employed to evaluate amine content, equilibrium CO2 uptake, amine efficiency, and adsorption kinetics of the materials. The water amount used during synthesis was found to play a crucial role in facilitating the attachment of amines to the silica surface, with higher water amounts increasing nitrogen content, indicating successful grafting. However, under dry CO2 conditions (400 ppmv, 25 °C), materials with the highest amine loadings exhibited lower CO2 uptake due to pore accessibility issues. These findings emphasize the importance of precise control over water and amine amounts to maximize performance.
The top-performing material, with the highest CO2 uptake and fastest kinetics, underwent 50 adsorption-desorption cycles. Regeneration at 120 °C in N2 showed stable performance, retaining 99% of its initial CO2 uptake. Column-breakthrough testing under humid CO2 conditions confirmed moisture enhances CO2 uptake in amine-modified materials. These results highlight the strong potential of aminosilicas for DAC applications, offering a pathway for tackling climate change.

Keywords: Direct Air Capture, Aminosilica, CO2 Capture