The co-promoting mechanism of EMEA/DEEA/PZ ternary water-lean solvent on CO2 capture- a study based on 13C-qNMR and DFT calculations

Amine based CO2 absorption is currently the most promising means of capturing CO2 in industry, and the waterlean amine solvent has received widespread attentions. The reaction mechanism of the EMEA/DEEA/PZ ternary water-lean amine solvent (WLS) during the process of CO2 capture was investigated theoretically to understand the synergistic effect between the different amine components. The concentrations of intermediate products were analyzed by 13C-qNMR (quantitative Nuclear Magnetic Resonance) spectroscopy, while the reaction mechanisms were calculated using gaussian 16. The NMR results showed that carbamate (EMEACOO-), HCO3-/CO32- were the main products in the carbon capture process of EMEA WLS. The protonated amine concentration varies according to the change of carbon dioxide concentration. The balance between deprotonation (forming carbamates) and CO2 removal (regenerating EMEA) depends largely on how ampholytes interact with nearby water molecules. The DFT result showed that EMEA is the key component of CO2 capture, while DEEA and PZ primarily assist in transferring protons, catalyzing the conversion of H2CO3 into HCO3- to accelerate the process of CO2 capture. Furthermore, they assist in the redaction of EMEAH+ to EMEA, allowing it continue to participate in capture reactions. DEEA, PZ and water could promote activating the protonated EMEA and enhanced its capacity of CO2 capture. Furthermore, the desorption process confirmed the proton transfer from DEEAH+, ultimately leading to the regeneration of EMEA, thereby demonstrating the effective performance of regeneration.