Experimental and Computational Study of CO2 Storage and Sequestration with Aqueous 2-Amino-2-hydroxymethyl-1,3-propanediol (TRIS) Solutions

Experimental solubility data of CO2 in (5 and 10) mass% TRIS aqueous solutions were measured at (318.15 and 333.15) K and up to 10 MPa. The solubility data were well correlated with the modified Kent-Eisenberg model. The reaction mechanism, reaction energies, and equilibrium constants for the formation of bicarbonate and carbamate from CO2, H2O, and TRIS were studied using the quantum-chemical approach COSMO-RS (conductor-like screening model for real solvents) at the BP/TZVP level. The bicarbonate and carbamate formations were confirmed by using Fourier transform infrared (FTIR) spectroscopy. The results demonstrate that the formation of the bicarbonate anion is the main product formed by the direct reaction of CO2 with water and TRIS, and reveal that the carbamate anion was formed by a proton transfer from TRIS-CO2 zwitterion to TRIS. Density functional theory (DFT) calculations with transition-state optimization and intrinsic reaction coordinate (IRC) in water using IEF-PCM solvation model at the B3LYP/6-311++G(d,p) levels of theory were employed to support the reaction pathway for the bicarbonate and carbamate formations. The conversion of the absorption product to stable carbonate (CaCO3) was also investigated experimentally by adding various Ca2+ sources, CaCl2\center dot 2H(2)O aqueous solution, and artificial seawater.