Computational Predictions of Thermophysical and Transport Properties of Aqueous Ionic Amines for Carbon Capture.

Growing concerns about the buildup of CO2 in the environment and its impact on climate have been at the forefront of new research. Means to remove carbon dioxide are of particular interest as the world begins to transition to more carbon neutral sources of energy as well as in environments such as the international space station (ISS) and deep-sea substations that require closed air revitalization. Buildup of carbon dioxide can cause structural damage to steel and pose a threat to humans. The ISS currently uses a zeolite to separate CO2 from cabin air, instead of monomethylamine (MEA), since the latter is volatile with a foul odor and relative toxicity. The process with zeolites is less than ideal since it requires pretreatment with a dessicant bed, a fair amount of energy to regenerate the zeolite, and it also suffers from the generation of dust particles that can be transmitted within the cabin.

A proposed solution for the ISS is the use of aqueous ionic amines (AIA), which reactively capture CO2, similar to MEA, but which are non-volatile due to their ionic nature. To evaluate their efficacy for the removal of CO2 one could model the overall process, however this first requires a detailed knowledge of the AIA’s thermophysical and transport properties. Here, we use molecular dynamics simulations to model the AIAs at different concentrations with and without carbon dioxide and to predict their concentration dependent properties. We determine the effect of water and the CO2 capture-reaction on the local ion-water structure, excess volumes, hydrogen bonding, heat capacity, viscosity, and species diffusivity. Knowledge of these properties will allow us to develop a full, macroscopic model of the CO2 capture process with AIAs in anticipation of their replacement as the primary capture media on the ISS.