Effects of Amine Structures on Oxidative Degradation of Amine-Functionalized Adsorbents for CO2 Capture

A series of adsorbents containing different amines including diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, branched poly(ethylenimine), and spermine were exposed to flowing O2 at accelerated temperatures of 80 and 100 °C. Herein, we evaluated the structural effects of amines on the stability of CO2 adsorbents in dry and wet O2-containing environments. Various techniques were used to characterize the adsorbents. The CO2 adsorption capacity of the sorbents was drastically reduced after exposure to dry O2-containing environments. Sorbents modified with amines with a high molecular weight and a long chain of alkyl linkers between amine functional groups exhibited high resistance to O2. The viscosity of the amines played an important role in the oxidative stability of the amine composites as it affected the mass transfer of O2 to the amine sites of the composites. Furthermore, we report for the first time that the presence of steam in O2 medium could suppress or accelerate the oxidative degradation of amine-based CO2 sorbents depending on the amine structure.