Novel Ternary Absorbent: Dibutylamine Aqueous-Organic Solution for CO2 Capture

Amine aqueous-organic solution is a novel ternary absorbent for CO2 capture. In the present work, 0.5 mol L-1 dibutylamine (DBA)/water/ethanol was chosen as the ternary mixed absorbent to obtain high absorption capacity and regeneration efficiency. The results demonstrated that the DBA/water/ethanol solution took into account the advantages of aqueous and non-aqueous solutions. When the volume ratio of water and ethanol was 5:5 at 313 K, the absorption loading reached a maximum of 0.82 mol mol(-1), which was higher than that of DBA/ethanol or DBA/water, and the viscosity of saturated solution was only 1.72 mPa s. Meanwhile, the regeneration efficiency of saturated DBA/water/ethanol solution reached 97.6% at 373 K for 30 min and still obtained 94.3% after the fifth regeneration cycle. Moreover, the detailed absorption/desorption mechanisms could be explained by carbon-13 nuclear magnetic resonance that DBA initially reacted with CO2 to form carbamate and then carbamate further reacted with water and ethanol to form HCO3- and C2H5OCO2- . During the absorption process, HCO3- and C2H5OCO2- could be converted into each other in the water/ethanol mixed solvent and finally reached equilibrium. In addition, the high regeneration efficiency of the DBA/water/ethanol solution was attributed to the reason that all carbamate converted to carbonates of HCO3- and C2H5OCO2- in the saturated solution and HCO3- and C2H5OCO2- decomposed more easily than carbamate during desorption.