Deep eutectic solvents for CO₂ separation from natural gas: Mechanistic insights and comparative performance
Year: 2026
Type: article
Abstract: Separating CO₂ from natural gas is essential for meeting pipeline specifications and enabling CO₂ reinjection for geological storage or enhanced gas recovery. Although CH₄ typically dominates natural gas, CO₂ removal from C₂H₆-containing streams remains challenging. Under liquefied conditions, the CO₂–C₂H₆ azeotrope limits conventional separation efficiency, while molecular sieves often preferentially adsorb C₂H₆ over CO₂. Choline chloride-ethylene glycol (ChCl-EG) deep eutectic solvents (DESs) offer tunable media for physical CO₂ absorption, with potential advantages in gas-loading capacity and regeneration-energy requirements. Here, molecular dynamics simulations were used to elucidate the separation mechanism and evaluate ChCl–EG DESs for CO₂ removal from natural gas across different DES formulations, gas compositions, and temperature–pressure conditions. The simulations show preferential CO₂ absorption over CH₄ and C₂H₆, with higher EG molar ratios promoting gas penetration into the DES phase. Hydrogen-bond analysis reveals that Cl − –EG interactions dominate the DES network, with each ChCl unit coordinating approximately three EG molecules in EG-rich systems. Two separation configurations were examined: cyclic absorption–desorption and DES-filled membranes. Within the molecular-scale membrane model, ChCl/EG (1:2) maximized CO₂ selectivity and enriched CO₂ from 60.0 to 94.9 mol% in the CO₂-rich feed. ChCl/EG (1,4) balanced selectivity and gas transport and enriched CO₂ from 15 to 69 mol% in the CH₄-rich feed in a single simulation step. C₂H₆ permeation remained limited in both cases. These findings highlight DES-filled membranes as promising platforms for CO₂ capture from C₂H₆-containing natural gas.
Authors: Le Zhang, Yunfeng Liang, Gyuhwan Jo, Takeshi Tsuji
Institutions: The University of Tokyo, Eneos (Japan)
Language: English
Subfield: Filtration and Separation
Field: Chemical Engineering
Domain: Physical Sciences
SDG: Climate action
Open Access status: hybrid
Estimated APC paid: $4,060
OpenAlex ID: W7225614750