An Electrochemically Mediated Amine Regeneration Process with a Mixed Absorbent for Postcombustion CO₂ Capture

Abstract

Electrochemically mediated amine regeneration (EMAR) was recently developed to avoid the use of thermal means to release CO 2 captured from postcombustion flue gas in the benchmark amine process. To address concerns related to the high vapor pressure of ethylenediamine (EDA) as the primary amine used in EMAR, a mixture of EDA and aminoethylethanolamine (AEEA) was investigated. The properties of the mixed amine systems, including the absorption rates, electrolyte pH and conductivity, and CO 2 capacity, were evaluated in comparison with those of solely EDA. The mixed amine system had similar properties to that of EDA, indicating no significant changes would be necessary for the future implementation of the EMAR process with mixed amines as opposed to that with just EDA. The electrochemical performance of the mixed amines in terms of the cell voltage, gas desorption rate, electron utilization, and energetics was also investigated. A 50/50 mixture of EDA and AEEA displayed the lowest energetics: ∼10% lower than that of 100% EDA. With this mixture, a continuous EMAR process, in which the absorption column was connected to the electrochemical cell as the desorption stage, was tested over 100 h. The cell voltage was very stable and there was a steady gas output close to theoretical values. The desorbed gas was further analyzed and found to be 100% CO 2 , confirming no evaporation of the amine. The mixed absorbent composition was also characterized using titration and nuclear magnetic resonance (NMR) spectroscopy, and the results showed no amine degradation. These findings that demonstrate a stable, low vapor pressure absorbent with improved energetics are promising and could be a guideline for the future development of EMAR for CO 2 capture from flue gas and other sources.

A State‐of‐the‐Art Update on Integrated CO2 Capture and Electrochemical Conversion Systems

“…A final alternative is promoting the electrochemically mediated amine regeneration, where heating is no longer required. The latter is discussed in more detail later in section 3.1 [43,44] …”

Perspective and challenges in electrochemical approaches for reactive CO2 separations

“…These challenges have been addressed with some success by the electrolyte design and formulation. For example, an addition of a less volatile amine to the ethylenediamine (EDA) electrolyte could suppress the vapor pressure maintaining the CO 2 capture efficiency, and an addition of an anionic surfactant, sodium dodecyl sulfate, could notably reduce the overall cell resistance ( Rahimi et al., 2020c , 2020d ). Very recently, a process similar to EMAR was demonstrated ( Li et al., 2020 ), except the system produces electrical power from the energy of the absorption process that would be otherwise lost to heat dissipation.…”

Selective Electrochemical Regeneration of Aqueous Amine Solutions to Capture CO2 and to Convert H2S into Hydrogen and Solid Sulfur

“…This is shown in Figure 1A. The team of Hatton et al [11][12][13][14][15][16][17][18][19][20] at MIT developed a post-combustion CO 2 capture scheme with an electrochemistry mediated aqueous amine regeneration (EMAR). Here, instead of thermally regenerating the solvent to capture CO 2 , electrochemistry is used.…”