Dissertation Defense: Haley Maren Stowe

First-Principles Investigation of Aqueous Amine-Based Solvents for Carbon Dioxide Capture

Haley Maren Stowe
Supervised by: Dr. Gyeong S. Hwang

Aqueous amine-based chemical scrubbing has been considered the most promising near-term solution for CO2 capture from flue gas, yet the underlying reaction mechanisms are still not fully understood. Moreover, its widespread implementation is hindered by the high cost associated with the parasitic energy consumption during solvent regeneration, along with degradation and corrosion problems. First-principles-based atomistic modeling can play a significant role in elucidating the complex physicochemical phenomena underlying CO2 reaction-diffusion behavior in aqueous amine-based solvent, especially when direct experimental characterization at the atomic level may be difficult. An improved fundamental understanding of these reaction mechanisms and intermolecular interactions can be used to provide explanations for experimental observations and fundamental data, and improve kinetic and thermodynamic models for process optimization.

Here, our recent theoretical works on the molecular mechanisms underlying CO2 capture and solvent regeneration in aqueous amines are presented. Through systematic comparative analyses of primary, tertiary, and sterically hindered amines, and diamines, we provide significant insights into how the mechanisms and rates of competing CO2 absorption routes can be influenced by the solvent structure, the relative strengths of intra- and intermolecular hydrogen bond interactions, and steric constraints. We also use a theoretical approach to examine the mechanisms occurring during thermal degradation, as well as the process underlying leaching of metal ions into solution due to corrosion and subsequent oxidative degradation, which remain unclear. These studies further demonstrate the importance of a detailed atomic-level description of the solution structure and dynamics to describe the reactions and in predicting the thermodynamic and kinetic properties in CO2-loaded aqueous amines. Moreover, an accurate description of solvent composition near the gas interface and near the iron surface is critical in predicting the CO2 capture and corrosion processes, respectively.

This dissertation highlights the increasingly important role of first-principles-based computer simulations in the detailed mechanistic study of CO2 capture by amine-based solvents, including solvent degradation and corrosion processes. The improved understanding gained from computational studies combined with experiment validations will greatly aid in the design and development of new solvents and inhibitors in efforts to improve the efficiency of commercial-scale applications.