CO2 capture performance of a 1-dimethylamino-2-propanol/N-(2-hydroxyethyl) ethylenediamine biphasic solvent

Abstract

Biphasic solvents are widely used for CO2 capture owing to their low regeneration heats; however, they typically suffer from poor regeneration performance and excessive energy consumption. In this study, a mixture of 1-dimethylamino-2-propanol (1DMA2P) and N-(2-hydroxyethyl) ethylenediamine (AEEA) was proposed for CO2 capture. By optimizing the 1DMA2P and AEEA concentrations, this biphasic solvent achieved superior phase separation and excellent absorption and regeneration performance. The proportion of CO2-rich phase was 66.67 %, with a CO2-rich phase loading of up to 5.07 mol/L. The desorption rate was improved by 106.7 % compared to that of conventional 5 mol/L monoethanolamine, and the regeneration efficiency up to 71.8 % in 60 min. Initially, CO2 reacted with AEEA at a faster rate to form a carbamate product. Subsequently, 1DMA2P acted as a proton acceptor, facilitating the formation of bicarbonates and carbonates. Nuclear magnetic resonance analysis indicated that the reaction products (AEEACOO-, AEEAH+, and HCO3–/CO32–) migrated to one phase, whereas 1DMA2P and any unreacted AEEA migrated to the other phase. Additionally, the disparity in polarity between the reactants and reaction products constituted the primary determinant for the phase transition. Notably, the regeneration heat of the 1DMA2P/AEEA biphasic solvent (1.83 GJ/t CO2) was approximately 54.1 % lower than that of conventional 5 mol/L monoethanolamine. Owing to its superior absorption properties, excellent regeneration performance, and low regeneration heat, the 1DMA2P/AEEA biphasic solvent is a promising candidate for practical CO2 capture systems.