A novel approach to high-pressure CO2 absorption with deep eutectic solvents: Quantitative analysis of physicochemical contribution and low regeneration energy insight

Carbon dioxide (CO 2 ) removal from syngas is an essential pretreatment in chemical production to control syngas quality and utilize carbon resource. Current decarbonization technologies are effective, however, they always consume large amounts of energy and require more economical absorbent in industry. This work introduced a deep eutectic solvent (DES) (4-aminopyridine: ethylene glycol, AP:EG), which was demonstrated to absorb CO 2 mainly by physical absorption (high capacity) and secondly by chemical absorption (thorough residual removal) at high pressures. At 303.15 K and 1 MPa, AP:EG (1:3) DES exhibited the best performance, and the total absorptive ability was 0.242 g CO 2 /g DES (30.34% chemical, 69.66% physical). The DES released absorbed CO 2 completely within 20 min under N 2 purging and maintained 99.3% capacity after five cycles, suggesting a scalable route toward low-energy high-pressure CO 2 capture. Owing to the predominantly physical mechanism, the regeneration energy was only 1.57 GJ/t CO 2 , markedly lower than typical aqueous amine systems (0.36 g CO 2 /g MEA, 3.5 GJ/t CO 2 ), while avoiding the low-temperature operation and volatility concerns associated with methanol-based physical absorption processes. Molecular simulations revealed that hydrogen bonding between EG and AP activated the amine site and reduced steric hindrance, enabling synergistic physiochemical uptake.