Synergistic Reaction Pathway Regulation and Process Simulation of Piperazine-Promoted AMP-EG Water-Reduced Absorbents for Low-Energy CO2 Capture

Abstract An AMP-PZ-EG-H2O water-reduced absorbent was developed for CO2/CH4 separation in natural gas decarbonization. Promoter screening and composition optimization identified PZ as the preferred promoter and an AMP/PZ mass ratio of 2:1 with a total AMP-PZ-EG mass fraction of 50 wt % as the best performance–viscosity compromise. The formulation exhibited a CO2/CH4 separation factor of 831, a CO2 recovery of 98.8%, and an apparent desorption enthalpy of 14.1 kJ/mol at high CO2 loading. 13C NMR and FTIR supported the coexistence of PZ-derived carbamate, AMP-associated bicarbonate, and a possible EG-related carbonate species. After three absorption–thermal regeneration cycles, 96.4% of the initial total titratable alkalinity was retained, and headspace GC-MS showed no monotonic increase in the minor peak tentatively assigned to 4,4-dimethyloxazolidine. An ELECNRTL-based Aspen Plus model predicted 96.41% CO2 removal, 1.20 mol % dry-basis CO2 in the sweet gas, and 98.91% CH4 recovery.