Cu(II)-Assisted CO2 Absorption and Desorption Performances of the MMEA–H2O System
The complexation of metal ions and amines can mediate the chemical equilibrium and the thermal effect between amines and CO2, thus promoting the absorption and desorption of CO2 in amine absorbents. In this work, the effects of Cu(II) on the performances of CO2 absorption and desorption in the Cu(II)–MMEA (2-(methylamino)ethanol)–H2O system were studied. The thermal desorption results show that the temperature increase during CO2 absorption can be mitigated in the presence of Cu(II), and the desorption performance of CO2 can be obviously improved at 75–95 °C. Using the thermal desorption at 85 °C, the CO2 desorption efficiency of MMEA solution containing 0.1 M [Cu] is 16.4% higher than that without cupric ions, and the regeneration energy consumption is reduced by 25%. The electrochemical research results indicate that the electrode structure and temperature affect the electrolysis rate of anodic copper, and the temperature is the key factor to enhance the CO2 desorption rate. Only considering the decomposition voltage, the energy consumption of the absorbent regeneration is 0.5 GJ/t CO2 at 50 °C, which is much lower than that of the thermal desorption method. The anode current efficiency is always about 100%. Increasing the temperature can increase the cathode current efficiency. When nickel foam with a large specific surface area is used as the cathode, the current efficiency can be increased to 100% at 50 °C. The CO2 desorption is significantly improved in a Cu(II)-assisted MMEA–H2O system. The electrochemical method can achieve a desired desorption at a relatively low temperature and greatly reduce the energy consumption of amine absorbent regeneration.
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