Systematic Investigation of the Thermodynamic Properties of Amine Solvents for CO2 Chemical Absorption Using the Cluster-Continuum Model

作者：Teranishi Kei; Ishikawa Atsushi; Sato Hiroshi; Nakai Hiromi

来源：Bulletin of the Chemical Society of Japan, 2017, 90(4): 451-460.

DOI：10.1246/bcsj.20160375

Accurate condensed-phase quantum chemical calculations employing the continuum cluster model were undertaken to systematically examine the reactivity of amine solvents with CO2, a reaction of great importance in CO2 capture and storage technologies. Thirteen amine compounds, including primary, secondary, tertiary, and hindered amines, were considered, and up to ten solvent water molecules were modeled explicitly including continuum solvation. Amine pK(a) values and reaction Gibbs energies for the formation of bicarbonate, carbamate, and zwitterions were evaluated. Our calculations indicate that increasing the number of explicit water solvents (n) steadily improves computational accuracy, reducing the mean absolute deviation (MAD) of the calculated pKa from the experimental values, i.e., 13.0, 8.6, 1.3, and 0.9 (in pK(a) units) at n = 0, 1, 6, and 10, respectively. Reaction Gibbs energies calculated with large n for the studied reactions were consistent with the experimental observation that carbamates are the most stable product species, although their stability is lower for secondary amines. However, at n = 0 or 1, positive reaction Gibbs energies were predicted, suggesting that bicarbonate formation would not occur. These results strongly indicate that the trend in the reactivity of CO2-amine reactions can only be correctly predicted by modeling solute-solvent interactions accurately.

• 出版日期2017-4