Mitigating Amine Oxidative Degradation via H-Abstraction Control in Structurally Robust Composite Amines

Amine-solvent degradation stands as a key bottleneck hindering the large-scale application of post-combustion CO2 capture, motivating the development of more chemically stable solvent chemistries. High-resolution mass spectrometry and density functional theory were combined to identify degradation pathways and quantify hydrogen-abstraction barriers. Sterically hindered and cyclic amines suppress hydrogen abstraction and downstream oxidation. Solvent degradation was evaluated in high-pressure autoclave reactors under simulated industrial flue-gas conditions representative of coal-fired power plants, with CO2 concentrations of about 10−15 vol %, O2 at several volume percent, and temperatures relevant to absorber−stripper operation and solvent circulation. Compared with conventional monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP) reduced degradation rates by 25−60%, attributable to steric hindrance that suppresses carbon-chain hydrogen abstraction. Under all tested operating conditions, a mixed solvent system comprising N-aminoethylpiperazine (AEP) and AMP demonstrated markedly stronger antidegradation capability than MEA. Antioxidants mitigated oxidative degradation, whereas Fe2+ accelerated it; chelating agents suppressed Fe2+-catalyzed oxidation by limiting peroxyradical formation. Structure−stability relationships and targeted additive design guided multifactor optimization of the absorbent formulation, improving stability by 71.6% under accelerated degradation tests and supporting long-term, oxygen-tolerant operation.