(264c) First-Principles Insights into Thermal Degradation Mechanisms of Aqueous 2-Amino-2-Methyl-1-Propanol (AMP) for CO2 Capture

2-Amino-2-methyl-1-propanol (AMP) has been considered an attractive amine-based solvent for CO₂-capture, but its thermal degradation still remains a challenge. In this talk, based on first-principles simulations, we will present the underlying reaction mechanisms of AMP degradation to cyclic 4,4-dimethyl-1,3-oxazolidin-2-one (DMOZD), a major product, in CO₂-loaded aqueous solution. We have evaluated possible degradation pathways including the relative stabilities of intermediates and products based on implicit solvent calculations, and then predicted the free-energy barriers for key elementary steps using metadynamics-biased ab initio molecular dynamics. Our calculations show that DMOZD may be formed from carbamic acid of AMP primarily following a direct ring-closure mechanism. This is in contrast to the case of monoethanolamine (MEA) in which the formation of cyclic 2-oxazolidinone (OZD), the primary initial product, is more likely to occur through an isocyanate intermediate. Our work also demonstrates that the reaction of DMOZD with AMP can be markedly suppressed compared to the reaction of OZD with MEA which leads to the formation of more stable products in aqueous MEA. Our further analyses clearly illustrate that the presence of methyl groups in AMP derivatives makes their solvation structure and dynamics noticeably different from those of MEA derivatives. The solvation effect turns out to be largely responsible for the distinct difference in degradation behavior between AMP and MEA in aqueous solution.