Cu(II)-Assisted CO₂Absorption and Desorption Performances of the MMEA–H₂O System

Abstract

The complexation of metal ions and amines can mediate the chemical equilibrium and the thermal effect between amines and CO 2 , thus promoting the absorption and desorption of CO 2 in amine absorbents. In this work, the effects of Cu(II) on the performances of CO 2 absorption and desorption in the Cu(II)− MMEA (2-(methylamino)ethanol)−H 2 O system were studied. The thermal desorption results show that the temperature increase during CO 2 absorption can be mitigated in the presence of Cu(II), and the desorption performance of CO 2 can be obviously improved at 75−95 °C. Using the thermal desorption at 85 °C, the CO 2 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 CO 2 desorption rate. Only considering the decomposition voltage, the energy consumption of the absorbent regeneration is 0.5 GJ/t CO 2 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 CO 2 desorption is significantly improved in a Cu(II)-assisted MMEA−H 2 O system. The electrochemical method can achieve a desired desorption at a relatively low temperature and greatly reduce the energy consumption of amine absorbent regeneration.

CO2 absorption into primary and secondary amine aqueous solutions with and without copper ions in a bubble column

“…Only a very small fraction of the copper(II)-amine complexes can form free amines as a result of the reverse reaction. Thus, the concentration of free amines in this system is smaller compared to that of copper-free amine solutions since most of the copper(II)-amine complexes are not regenerated as free amine due to higher equilibrium constants of copper (II)-amine complex formation reactions [ 26 , 38 ]. As a result, CO 2 loading in systems containing copper (II) ions decreases.…”

Recent Progress on CO2 Capture Based on Sterically Hindered Amines: A Review

“…(3) Yoon, B.; Hwang, G. S. First-principles assessment of anomalous thermal degradation of aqueous 2-amino-2-methyl-1-propanol for CO 2 capture. Energy Fuels 2021, 35 (20), 16705−16712.…”

“…The emission of an inordinate quantity of greenhouse gases into the atmosphere has been recognized as a significant instigator of worldwide climate alteration. − Carbon dioxide (CO 2 ) is one of the most prominent greenhouse gases. − The emission of CO 2 into the atmosphere is a major environmental concern as it has a direct impact on the rising temperatures of the planet. − As per the statistics published by the International Energy Agency, the worldwide CO 2 emissions stemming from energy utilization surged to an all-time high of 36.3 billion tons in 2021, which marks a 6% rise in contrast to the figures for 2020 . Fossil fuel combustion is responsible for more than two-thirds of the world’s net CO 2 emissions for electricity and heat production. − The implementation of carbon capture, utilization, and storage (CCUS) is widely regarded as a pivotal technology in mitigating CO 2 emissions by the year 2050. − As shown in Figure , CCUS involves the capture of CO 2 from sources like power plants and industrial processes, followed by the storage of CO 2 in underground geological formations or the utilization of it for other purposes such as enhanced oil recovery. − According to the location of CO 2 capture, there are precombustion capture, oxygen-rich combustion, and postcombustion capture. − Precombustion capture technology has high equipment investment costs and complex systems; oxygen-enriched combustion technology has high energy consumption in the oxygen production process. Postcombustion capture technology necessitates solely the adjustment of the tail gas treatment system of the power plant, thereby incurring measly modification expenses and exhibiting favorable adaptability to the power plant, rendering it a fitting option for retrofitting extant power plants. − Capturing CO 2 after combustion is seen as an essential measure toward decreasing worldwide emissions of CO 2 generated by the combustion of fossil fuels. − …”