Mechanism of CO2 capture into isophorone diamine-water binary solid-liquid biphasic absorbent
Solid-liquid biphasic absorbents offer the advantages of easy separation and operation due to the formation of a solid phase after CO2 capture,which can be separated by static precipitation.Howev-er,most existing absorbents require organic phase separators to regulate phase transition,leading to is-sues including volatile loss of phase separators and high viscosity of the rich liquid phase.In this study,a novel amine-water binary solid-liquid biphasic absorbent was developed.This absorbent exhibits solid-liquid phase change behavior without the need for an organic phase separator after CO2 absorption in the aqueous solution.Absorption experiments showed that the total absorption capacity of IPDA-H2O could reach 0.85 mol CO2·mol-1 at a concentration of 1.00 mol·L-1 and an absorption temperature of 313.15 K.After reaching saturation,CO2 was concentrated in the lower solid phase,which accounted for 43.60％of the total solution volume and contained 93.98％of the total absorption loading.The CO2-lean phase had a low viscosity of 1.08 mPa·s.After being hot-melted,the solid products were regen-erated at 393.15 K for 60 min,with a regeneration efficiency of 98.31％.Even after 5 absorption and desorption cycles,the regeneration capacity remained above 80％of its initial capacity,indicating good regeneration stability.13C NMR spectra showed that most of the IPDA-carbamate and its decomposition product,bicarbonate,were concentrated in the rich solid phase,while a small amount of unprecipitated carbamate and water were present in the lean phase.13C NMR spectra indicated that CO2 was almost completely released from IPDA-H2O,demonstrating the system's excellent absorption-de-sorption performance.Quantum chemical calculations revealed that IPDA and H2O had similar dipole moments before CO2 absorption,indicating similar polarity and high mutual solubility.After absorption,the dipole moment of the products decreased.Additionally,the intramolecular hydrogen bonding within the products was found to be stronger than the bonding between the product and water.This increase in the product's lattice energy drives the precipitation of the product carbamate,resulting in a solid-liquid phase transition.
CO2 captureSolid-liquid biphasic absorbentOrganic amineAbsorption-desorption per-formanceReaction mechanism
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