CO₂‑Induced Degradation of Amine-Containing Adsorbents: Reaction Products and Pathways

A comprehensive study was conducted to investigate the stability of a wide variety of mesoporous silica-supported amine-containing adsorbents in the presence of carbon dioxide under dry conditions. CO₂-induced degradation of grafted primary and secondary monoamines (pMono, sMono), diamines with one primary and one secondary amines (Diamine) and triamine with one primary and two secondary amines (TRI) as well as different impregnated polyamines such as branched and linear polyethylenimine (BPEI and LPEI) and polyallylamine (PALL) was investigated using extensive CO₂ adsorption–desorption cycling as well as diffuse reflectance infrared Fourier transform (DRIFT) and ¹³C CP MAS NMR measurements. Except for sMono, all other supported amines underwent significant deactivation in the presence of dry CO₂ under mild conditions. In all cases, the decrease in CO₂ uptake was associated with the formation of urea linkages at the expense of amine groups. The urea-containing species were identified, and the deactivation pathways were delineated.