Thermal degradation and inhibition of long-chain triamines for CO2 capture: An integrated experimental and computational study

Amine-based CO 2 capture is a mature and commercially established technology. High-temperature regeneration causes amine thermal degradation, decreasing capture performance. The thermal stability of four long-chain triamines (N-C-C-C-N-C-C-C-N backbone) was evaluated and the inhibitors were screened. Degradation rates were monitored by gas chromatography and degradation products were characterized using ion chromatography and gas chromatography – mass spectrometry. Quantum chemical calculations and ReaxFF molecular dynamics simulations were employed to elucidate the degradation and inhibition mechanisms. The results indicate that triamines degrade rapidly via a radical-based mechanism. Formate and acetate were identified as the major anionic products, while low-molecular-weight fragments dominated the organic products. Under the tested conditions, the degraded solutions shows slight losses in CO 2 capture performance, but the performance losses were limited. Longer chains decrease the bond dissociation energy of C N and C C bonds and degradation is initiated by homolytic scission of C H and C N bonds, generating radical species and triggering subsequent radical reactions. The addition of 2-ethyl-4-methylimidazole enabled triamines to maintain a residual amine ratio of 80% even after thermal treatment at 423.15 K for 6 days by enhancing local electron density and forming stable non-covalent interactions with the triamines. This work provides insights for the development of high-stability amine-based solutions.