Toward Stable CO 2 Capture in Combined Cycle Gas Turbine Flue Gas: Degradation-Resistant Biphasic Absorbents Enabled by Amine Blending and Radical Scavenging

Developing amine-based absorbents with superior degradation resistance is essential for achieving efficient and cost-effective carbon capture from the high-oxygen flue gas emitted by combined cycle gas turbine (CCGT) power plants. This study focuses on a promising biphasic absorbent based on 3-(dimethylamino)-1-propylamine (DMPDA), aiming to systematically address its degradation under high-oxygen conditions. A synergistic strategy was adopted, beginning with the optimization of the absorbent composition to enhance its intrinsic stability. Subsequently, a high-temperature-resistant degradation inhibitor was screened and incorporated to mitigate degradation under stripper conditions. Through 1000-h simulated degradation tests, combined with analytical techniques such as HPLC, GC-MS, and potentiometric titration, a comprehensive evaluation was conducted of amine degradation kinetics, changes in absorption and desorption performance, and alkalinity loss across different formulations. The optimized formulation, D4M2(1:3), was identified, exhibiting a significantly higher postdegradation desorption efficiency (∼70%) compared to the unmodified system (∼23%). In inhibitor screening, sodium lignosulfonate (SL) demonstrated outstanding inhibition performance under high-temperature aerobic conditions. Mechanistic studies revealed that the phenolic hydroxyl and sulfonic acid groups in SL effectively scavenge free radicals, while its steric hindrance steers the degradation pathway from producing weakly basic tertiary amines toward generating more basic secondary or primary amines. This shift enables the absorbent to maintain high CO 2 capture performance and alkalinity after long-term degradation. The synergistic “formulation optimization-inhibitor addition” strategy established in this work provides a critical theoretical foundation and an industrially viable solution for enhancing the operational stability and service life of amine-based solvents in CCGT carbon capture systems.