Advancing energy-efficient CO2 capture with organic amine solutions using ionic liquid absorption promoters and zeolite molecular sieve desorption catalysts

Abstract

Alkanolamine solutions have been widely used for CO₂ capture due to their low cost and stable performance. However, their inherent structural limitations led to significant challenges, such as low CO₂ absorption–desorption capacity and high energy demands for regeneration. To address these issues, this work proposes an efficient CO₂ capture system that employs 2-(2-aminoethylamino)ethanol (AEEA) as the primary absorbent due to its stable performance, amino-functionalized ionic liquid (AIL) synthesized via a one-step method as absorption promoters, and an appropriate amount of solid acid catalyst (SAC) as desorption catalysts. The experimental results demonstrated that the composite system comprising 20 wt% AEEA (primary absorbent), 10 wt% [DETAH][Pz] (absorption promoter), and 0.1 wt% HZSM-5 (desorption catalyst) represents the optimal configuration. The system achieved a CO₂ absorption capacity of 0.50172 g CO₂/g amine for the fresh solution, which decreased to 0.42619 g CO₂/g amine after five regeneration cycles, maintaining 84.95 % of the original capacity. The desorption ratio exceeded 85 %, while regeneration energy consumption was reduced by 30.22 % compared to the MEA/water system. Notably, the inclusion of the HZSM-5(21) catalyst significantly enhanced the CO₂ desorption process during the initial 20 min. The desorption amount increased by 62.78 % relative to the non-catalytic system, the average desorption rate improved by 40.85 %, and the peak desorption rate rose by 31.94 %, resulting in a more efficient and complete CO₂ desorption process. Analysis using ¹³C NMR demonstrated that the synergistic absorption effect between AEEA and [DETAH][Pz] significantly improved the CO₂ absorption capacity of the system. Meanwhile, the Brønsted and Lewis acid sites on the HZSM-5(21) molecular sieve, along with [Pz]-H, effectively facilitated the decomposition of carbamates, thereby catalyzing the CO₂ desorption process.