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

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journal contribution
posted on 17.10.2017, 00:00 by Guohua Jing, Fan Liu, Bihong Lv, Xiaobin Zhou, Zuoming Zhou
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.