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 O-2 at accelerated temperatures of 80 and 100 degrees C. Herein, we evaluated the structural effects of amines on the stability of CO2 adsorbents in dry and wet O-2-containing environments. Various techniques were used to characterize the adsorbents. The CO2 adsorption capacity of the sorbents was drastically reduced after exposure to dry O-2-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 O-2. The viscosity of the amines played an important role in the oxidative stability of the amine composites as it affected the mass transfer of O-2 to the amine sites of the composites. Furthermore, we report for the first time that the presence of steam in O-2 medium could suppress or accelerate the oxidative degradation of amine-based CO2 sorbents depending on the amine structure.