Polyethylene Glycol (PEG) Addition to Polyethylenimine (PEI)-Impregnated Silica Increases Amine Accessibility during CO₂ Sorption

Abstract

Amine-impregnated sorbents can be applied in CO2 sequestration, but they suffer from low amine utility due to slow diffusion of CO2, leading to reduced accessibility of buried amines. We examined silica-supported polyethylenimine (PEI) sorbents and blended them with polyethylene glycol (PEG) as an additive to study the role of PEG in modifying sorption performance. We report an increase in amine efficiency, a decrease in the heat of sorption and regeneration temperature, and a change CO2 amine speciation with the addition of PEG. The increase in viscosity due to CO2 sorption leads to greater diffusion resistance; increases in viscosity were lower during CO2 sorption in blends with higher PEG composition. 13C NMR results on CO2-saturated PEI–PEG blends revealed the formation of carbamic acid and carbamate and showed a larger fraction of carbamic acid in PEG-rich samples. We propose PEG increases the amine efficiency by enabling the diffusion of CO2 due to viscosity reduction and changes in the CO2-amine speciation (carbamate versus carbamic acid), which modifies the theoretical CO2/amine stoichiometry.

Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

“…29,35−37 The maximum uncertainty in the calorimetry measurements is estimated to be 10 kJ mol −1 through previous experiments with a similar setup. 38 In stark contrast, C 2 H 4 adsorption on the core−shell nanoparticles was much less exothermic, measuring 125 kJ mol −1 for 2 ML Pt/TiWC and below instrumental detection limits (∼20 kJ mol −1 ) for 2 ML Pt/TiWN as would be expected from the differences in amounts of C 2 H 4 adsorption and reactivity trends. Although C 2 H 2 appeared to adsorb more strongly on the core−shell nanoparticles than on Pt comm (260−290 kJ mol −1 vs 200 kJ mol −1 ), the number of adsorbed C 2 H 2 molecules was an order of magnitude lower.…”

“…Indeed, the heat of adsorption (Δ H ads ) measurements showed marked differences across samples. At 298 K, the Δ H ads for C 2 H 2 and C 2 H 4 on Pt comm was 200 kJ mol –1 and 190 kJ mol –1 , respectively, consistent with literature values. ,− The maximum uncertainty in the calorimetry measurements is estimated to be 10 kJ mol –1 through previous experiments with a similar setup . In stark contrast, C 2 H 4 adsorption on the core–shell nanoparticles was much less exothermic, measuring 125 kJ mol –1 for 2 ML Pt/TiWC and below instrumental detection limits (∼20 kJ mol –1 ) for 2 ML Pt/TiWN as would be expected from the differences in amounts of C 2 H 4 adsorption and reactivity trends.…”

Enhanced CO2 sorption in a hybrid PEI–Mo oxide film via pulsed electrodeposition

“…This quality remains important and amines can also dynamically change the sorbent viscosity through intermolecular cross-linking between the PEI chains during sorption. 6,18 In the silica-supported PEI, the silica primarily provides both an increased surface area and mechanical support for the active sorbent. A recent study in thin-film sorption showed the performance of thin films comprising magnesium and a metal-organic framework (MOF), synthesized via vapor-assisted crystallization, with the film thicknesses ranging from 55 to 1300 nm.…”

Amine-Infused Hydrogels with Nonaqueous Solvents: Facile Platforms to Control CO2 Capture Performance

“…17,21,22 In other literature reports, amines have been absorbed onto a physical framework. Utilizing solid supports such as mesoporous silica 16,23,24 and polymethylmethacrylate, 25,26 CO 2 sorption efficiency and kinetics were improved with an increased surface area for absorption and a simplified flow of gas. Solid absorbents have advantages over liquid-based systems: the CO 2 uptake can be higher, corrosion is minimized, properties such as ratios of amines to the solvent can be tuned, and viscosity changes with the CO 2 uptake are eliminated, which improves the gas flow.…”