(18c) Energy-Efficient and Stable Amine Structures Supported By Mesoporous Silica for Direct Air Capture

A large portion of CO₂ emissions in ~5.2 gigatons (Gt) is released in relatively small quantities from distributed sources emitted each year in the U.S. Therefore, for such emissions, point source CO₂ capture is not feasible and direct air capture (DAC) is an indispensable part of a diversified portfolio of technologies to mitigate U.S. greenhouse gas emissions. Successful DAC technologies require the separation of high purity CO₂ (e.g., >95%) with high selectivity toward CO₂, low energy requirements, minimum chemical and thermal degradations, reliability, long lifetime, etc.

In this regard, DAC technologies based on amine-based sorbents has emerged as one of the most promising approaches. However, amine-based sorbents are known for thermal and oxidative degradations and high desorption energy requirement for sorbent regeneration process due to high binding energy of amines toward CO₂. In this study, we examined various chemical modifications to amines for DAC and the impact of the modifications on CO₂ adsorption performances. In-situ FTIR spectroscopy has been implemented to probe the mechanism of the modifications for CO₂ adsorption and degradation on both unmodified and modified amine-based sorbents. The in-situ FT-IR results endorsed that unmodified amine sorbents exhibited strong chemisorption as well as high oxidative degradation compared to modified amine sorbents. Differential scanning calorimetry (DSC) results also supported that the heat of desorption requirement for modified amine-based sorbents are significantly lower than unmodified amine-based sorbents.