Degradation of amine-supported CO2 adsorbents in the presence of oxygen-containing gases

► The effect of air exposure on CO 2 adsorption over amine-grafted silicas was investigated using DRIFT and 13 C CP/MAS NMR. ► Materials containing primary and tertiary monoamines were found to be highly stable up to ca. 120 °C. ► Materials with secondary monoamine, or mixed amines such as triamine were very sensitive to air-exposure. Three samples containing grafted primary, secondary and tertiary monoamines (pMono, sMono and tMono) as well as a triamine-grafted material (TRI) with both primary and secondary amines were exposed to flowing air at 120 °C for 30–40 h. It was found that pMono and tMono were stable as evidenced by CO 2 adsorption measurements as well as infrared and NMR data, whereas sMono and TRI adsorbents exhibited extensive deactivation. Infrared data showed the development of an absorption band at 1665–1680 cm −1 whose intensity increased with the degree of oxidative degradation. However, only minor changes occurred in the corresponding 13 C CP/MAS NMR spectra. The findings were discussed, and a tentative explanation was provided.