Ether-functionalization of monoethanolamine (MEA) for reversible CO2 capture under solvent-free condition with high-capacity and low-viscosity
CO2 capture based on aqueous alkanolamines, in particular, monoethanolamine (MEA), currently represents the maturest technology, but is still limited by the inherent drawbacks of high energy consumption and low gravimetric capacity due to the involvement of water as solvent. In this work, ether-functionalization of MEA has been proposed to structurally modify this cheap industrial absorbent for CO2 capture under water-lean condition. The resulting ether-functionalized MEAs have been employed as solvent-free absorbents with enhanced gravimetric capacities (11-19 wt% at 25 oC, 12-20 wt% at 40 oC) and relatively low viscosities (as low as 311 cP at 25 oC, and 105 cP at 40 oC) at CO2-loaded state. The captured CO2 could be easily stripped out by heating at a relatively low temperature (75 oC). Such novel absorbents also exhibit excess absorption capacity under high operating pressures (20 and 30 bar), owing to the CO2-philic nature of ether group for additional physisorption. Furthermore, a clear structure-property relationship among these functionalized MEAs has been established through systematic investigation of their thermodynamic properties and absorption-desorption performance by means of density functional theory (DFT) calculations, 13C NMR spectroscopy, differential scanning calorimetry (DSC) and in situ FTIR analysis. Additionally, these newly identified MEA derivatives could provide considerable potential to use the already existing aqueous alkanolamine infrastructure for further cost saving.