Understanding dynamics and distributions of poly(ethylenimine) confined in mesoporous SBA-15 silica and impact on CO2 capture
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Moon, Hyun June
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Abstract
Solid-supported amines serve as advanced CO2 sorbents, effectively balancing high CO2 uptake and energy-efficient regeneration. These materials enable CO2 capture, even from ultra-dilute sources such as ambient air, which contains approximately 420 ppm CO2. One exemplary sorbent model is poly(ethylenimine) (PEI) in SBA-15. In this sorbent, the physical attributes of PEI dictate its performance. The distribution of PEI determines the extent of amines available for reacting with CO2, determining equilibrium CO2 uptake, while PEI mobility controls the diffusion of CO2 through the PEI-packed pore space, ultimately influencing CO2 uptake rates. This thesis aims to characterize the distribution and motions of PEI confined in SBA-15, utilizing a combination of neutron scattering, solid-state NMR, and molecular dynamics (MD) simulation. First, the effects of different pore wall-PEI interactions are studied, revealing subtle interplays among PEI, solid walls, and wall-grafted chains that result in unique PEI structures and mobilities. Second, the underlying roles of poly(ethylene glycol) (PEG) additives are illuminated, providing insights into the unique behavior observed in CO2 sorption and desorption processes. Finally, the impacts of multiple cycles and the composition of the input gas are investigated, demonstrating that repeated thermal swings and humidity in the input stream lead to changes in PEI properties.
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2023-12-06
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Dissertation