CO2 Absorption Process at the Liquid–Vapor Interface of Aqueous Monoethanol and Diethanol Amine Solutions

CO₂ postcombustion is a promising technique to reduce the amount of CO₂ emissions from fossil fuel power plants. Aqueous amine solutions are among the most mature approaches to remove CO₂ from fume gases, but further efforts are required to overcome obstacles like the high amount of energy needed to strip the amine from the CO₂. A better understanding of the chemical reactions and the distribution of the reaction products in the crucial liquid–vapor interface region is of great importance for a deliberate improvement of the amine solutions. Ambient pressure X-ray photoelectron spectroscopy with a colliding micro liquid flat jet system was used to study 30 wt % aqueous monoethanolamine and diethanolamine solutions with different loading of CO₂. The observed concentrations of the different species in the bulk of our amine solution are in excellent agreement with infrared spectroscopy and nuclear magnetic resonance measurements from literature. Additionally, there is indication that the formed carbamate amine show a slight surface propensity, while the pure amine show a small tendency for the bulk of the solutions for both amine solutions at low CO₂ loadings.