Synergistic enhancement of CO2 capture via a dual-activator strategy: Mechanism insights into tertiary amine-boosted absorption and alcohol-facilitated regeneration

Despite the advantages of low regeneration energy and corrosiveness, the CO 2 absorption loading capacity and regenerability of non-aqueous absorbents (NAAs) must be advanced to enable their viable practical application. This study introduced an innovative dual-activator strategy employing a tertiary amine and an alcohol to enhance both absorption and regeneration performance in primary amine–based NAAs. Experimental results showed that incorporating an appropriate amount of the tertiary amine N,N -dimethylethanolamine (DMEA) increased the CO 2 loading of the diamine 3-methylaminopropylamine (MAPA) to 1.54 mol·mol −1 MAPA, a 43.9% increase over the system without DMEA, while the addition of n-propanol (NPA) enabled highly efficient regeneration with 99.74% efficiency, a 27.2% improvement compared to the system without NPA. The absorbent also exhibited excellent cycling stability, maintaining 94.16% regeneration efficiency after five cycles. Mechanism investigations revealed that DMEA preferentially facilitated in the deprotonation of the MAPA-zwitterion during absorption, increasing the availability of free MAPA for CO 2 uptake and ultimately enhancing CO 2 absorption. During desorption, NPA served as a proton shuttle that redirected the proton transfer from a direct route to an indirect one via itself (protonated amine → NPA → MAPA-carbamate), significantly reducing the energy barrier. Meanwhile, NPA also participated in intermolecular proton exchange with the resulting carbamic acid, effectively promoting its thermal decomposition. Thermodynamics and corrosion analyzes confirmed that the optimized MAPA-DMEA-NPA system required only 0.43 GJ·ton −1 CO 2 in sensible and latent heat, 79.1% lower than the 30 wt% MEA solution, and exhibited negligible corrosiveness (2.5 × 10 −4  mm·year −1 on carbon steel). This work presented an effective dual-activator approach for designing high-performance NAAs with superior CO 2 capacity and regeneration stability, providing a promising pathway for advancing energy-efficient CO 2 capture technologies.