Effect of Solvents on the Phase Separation Behavior and CO2 Capture Performance of MEA-Based Nonaqueous Absorbents
Nonaqueous absorbents for CO2 capture have attracted great attention in research institutes recently because of their many advantages, such as energy efficiency and noncorrosiveness. Novel nonaqueous single-phase and biphasic absorbents have been developed. In this work, to satisfy application requirements, the effects of solvents on nonaqueous absorbents’ phase separation behavior and CO2 solubility were clarified. The nonaqueous absorbents comprising MEA and 26 kinds of solvents were investigated. The phase separation behavior after CO2 absorption, CO2 solubility, and CO2 cyclic capacity of nonaqueous absorbents were studied. The solvent polarity parameter ET(30) and the dielectric constant of solvents mainly affected the phase separation behavior and CO2 solubility of nonaqueous absorbents, respectively. The nonaqueous absorbent comprising a solvent with an ET(30) value larger than 50 kcal/mol maintained a single phase after CO2 absorption. The CO2 solubility of nonaqueous absorbents had a good positive relation with the dielectric constant of solvents. Moreover, nonaqueous absorbents comprising ethylene glycol monoethyl ether exhibited the optimal CO2 cyclic capacity and heat of CO2 absorption. In comparison to 30% MEA/H2O, the CO2 cyclic capacity of the nonaqueous absorbent increased by 51.8%, and the heat of CO2 absorption decreased by 35.4%.
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