DFT Study on Thermodynamic Parameters of CO2 Absorption into Aqueous Solution of Aliphatic Amines
- Received Date: 2014-06-19
- Density functional theory, Amine, CO2 absorption, Heat of absorption, SMD solvation model
Abstract: Using density functional theory (DFT), the thermodynamic parameters of the CO2 absorp-tion into the aqueous solution of the aliphatic amines including some alkylamines, alka-nolamines, diamines and a type of aminoamide were calculated. The geometry optimiza-tion and the calculation of vibrational frequencies in the gas phase were performed at the B3LYP/6-311+ G(d,p) level of theory. Moreover, the standard solvation free energies of the studied species were computed upon the solution phase optimized geometries through the latest continuum solvation model (SMD/IEF-PCM) at the HF/6-31G(d) level of theory. With this approach, two important properties of the CO2 absorption into the aqueous so-lutions of the studied amines were evaluated: the acid dissociation constant (pKa) of the parent amines and the standard enthalpy change (ΔH?abs) related to the CO2 absorption process. A roughly linear relationship was observed between pKa and ΔH?abs. This finding suggests that a raise in the basicity of an amine leads to an increase in the heat released in CO2 absorption and consequently in the required energy for the regeneration of amine.
|Citation:||Monireh Hajmalek, Hossein Aghaie, Karim Zare, Mehran Aghaie. DFT Study on Thermodynamic Parameters of CO2 Absorption into Aqueous Solution of Aliphatic Amines[J]. Chinese Journal of Chemical Physics , 2014, 27(6): 672-678. doi: 10.1063/1674-0068/27/06/672-678|