New Diffusive Intermediates Under Polar Condition for CO2 Adsorption in Silica-Supported Amine Sorbents

The adsorption process of CO₂ on highly loaded, silica-supported, polyethylenimine-impregnated sorbents has been investigated based on a reaction-diffusion model that takes zwitterions as the diffusive intermediate.  Simulation results qualitatively replicate the experimental results under dry conditions. An associated parameter sensitivity and quantum chemistry study shows that the diffusive intermediates control the capacity of CO₂ uptake in sorbents but that zwitterions are likely unstable under anhydrous conditions. Based on quantum chemical results, a new model proposes physically-bonded moieties involving water, amines and CO₂ as new diffusive intermediates.  The new model will be analyzed and compared with experimental TGA results.