Amines are the most widely used chemicals for CO2 capture, and are used in solvent-, solid sorbent-, and membrane-based systems. Amino groups react with CO2 to generate several ionic species, and these reactions are facilitated in polar environments and especially in aqueous solutions. Primary and secondary amines react with CO2 to form the carbamate anion and protonated amine as follows:2R1R2NH + CO2 ? R1R2NCOO� + R1R2NH2+ (1)where Rn represents an amino substituent. In the presence of water, another product of CO2 absorption is the bicarbonate anion.R1R2R3N + CO2 + H2O ? HCO3� + R1R2R3NH+ (2)The reaction mechanisms for CO2 absorption-desorption differ significantly depending on the environment surrounding the reaction system. Therefore, effects of surrounding environment on absorbent performance for CO2 capture have to be considered for exploring the properties required for efficient absorbents. In this context, we have theoretically investigated reactions including (1) and (2) in various amine-CO2 systems using density functional theory (DFT) calculations. The environments surrounding the amine-based absorbents are represented by modeling (i) vacuume, (ii) water, and (iii) amine solvents. Importantly, we revealed that solvation both in aqueous and neat amine solutions predominantly affects the CO2 absorption-desorption in terms of the changes in Gibbs free energy (?G) and enthalpy (?H) for the relevant reactions. In addition, substitution of amino group by some functional groups such as alkyl and alcohol groups with an optimal number of carbon atoms drastically improves absorbent performance for CO2 capture. On the bases of DFT and conductor like screening model for realistic solvents (COSMO-RS) approaches, we developed the model for predicting the stability of reaction products such as carbamate anion in reaction (1) for application as a tool in molecular design.

Computational study on the chemistry of amine-besed absorbents for CO<sub>2</sub> capture

247th National Meeting (2014)

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Computational study on the chemistry of amine-besed absorbents for CO2 capture

Computational study on the chemistry of amine-besed absorbents for CO₂ capture