CO₂ absorption mechanism in amine solvents and enhancement of CO₂ capture capability in blended amine solvent

The reaction mechanism for CO₂ absorption in amine solvent was investigated by theoretical analysis. The reactants were CO₂ and six amines, and the reactions were designed with or without additional water or amine molecule. These molecules increase the interaction between reactants and withdraw a proton from amino group of amine. From the additional amine model that shows lowest activation energy, zwitterionic and termolecular mechanisms seem to be suitable for CO₂ capturing reaction in amine solvents. Moreover, the additional amine model can be applied to understand the enhancement effect of CO₂ absorption in blended amine solvents. We report a new attempt that describes reaction mechanism in blended amine solvent by applying additional amine base. The results of CO₂ capture ability were analogous to experimental observation. Comparing our results and previous QM/MM and ab initio MD calculations, it was found that the QM treatment including the reactants and surrounding water molecules would be very critical and the QM region should be properly selected large enough in QM/MM.