An interactive chemical enhancement of CO2 capture in the MEA/PZ/AMP/DEA binary solutions

Chemical absorption is an effective method for CO2 capture. Due to their high absorption/desorption efficiency, amines have been used in single or blended form. Compared with the single ones, blended solvents usually show better absorption/desorption performance because of their interactive enhancement effect, however the mechanism is still unclear. In this study, the chemical interactive reaction is assumed to be one of the key factors for the enhancement. Based on this, the reactions of CO2 absorption in binary amine solvents (the binary mixtures of monoethanolamine (MEA)/piperazine (PZ)/2-amino-2-methyl-1-propanol (AMP)/diethanolamine (DEA)) have been investigated. The ab initio method with Density Functional Theory (DFT) is adopted in the simulations. Compared with other amines, numerical results showed that PZ presents the lowest forward energy barrier and the second lowest backward energy barrier in zwitterion formation. During the intermolecular hydrogen transfer processes, PZ shows a significant enhancement effect on MEA/DEA/AMP in the interactive reactions. For MEA, it shows an enhancing effect on AMP but hindering effect on PZ and DEA. Moreover, it was found that the MEA+COO− based reactions have good absorption property while the AMP+COO− based ones have good desorption performance. These findings reveal the interactive effect between different amines during the interactive reactions, which may provide theoretical instructions for solvent screening of blended solutions.