CO₂ absorption with diamine functionalized deep eutectic solvents in microstructured reactors

Deep eutectic solvents (DESs) have gained much attention to capture CO₂ nowadays because of their simpler synthesis, higher sustainability and better eco-friendly properties compared to ionic liquids and conventional amine sorbents. Herein, we analyzed the CO₂ absorption performance of five novel diamine functionalized DESs in microstructured reactors (MSRs) with metal foams as packing materials. Interestingly, the DES functionalized with N-methyl-1,3-propanediamaine (MAPA) showed remarkable absorption performance without significant viscosity rise. The CO₂ loading and absorption efficiency of this DES could reach 0.78 mol of CO₂ / mol of diamine and 98% at the gas to liquid flow rate ratios of 640 and 240, respectively. Even computational studies showed that the ethylenediamine (EDA) functionalized DES had the highest CO₂ uptake ability due to the low energy barrier, but sudden rise in viscosity of the EDA functionalized DES reduced its CO₂ absorption ability compared to the MAPA functionalized DES. Further experiments indicated that the MAPA functionalized DES showed low heat of absorption and remarkable regeneration ability. Overall rate constant and absorption flux of this DES were higher than most previously used amine functionalized DESs. Consequently, the unification of this remarkable DES and microreactors has great process intensification potential for CO₂ absorption.