Investigating H2O and CO2 co-adsorption on amine-functionalised solid sorbents for direct air capture

Direct air capture can be an invaluable technology to limit the devastating global temperature increase caused by anthropogenic emissions. Amine-functionalised porous adsorbents combined with temperature-vacuum swing regeneration can remove carbon dioxide from the air in high purities and hence is a promising technology for direct air capture. An example, of a commercially available amine-functionalised adsorbent, Lewatit VP OC 1065®, is selected for study in this work. These materials selectively adsorb high quantities of carbon dioxide. However, they also adsorb significant amounts of water. Mechanistic mathematical descriptions of this multi-component adsorption do not currently exist, leading to inaccurate performance estimates from process modelling. In this study, we will present mathematical descriptions based on equilibrium and dynamic co-adsorption data. This expands the co-adsorption isotherm modelling on the previous empirical approaches detailed in literature. [1], [2] Meanwhile, we will present the effect of water on carbon dioxide adsorption kinetics for the first time. These results will lead to better modelling and improved optimisation of direct air capture processes. We also believe that water and carbon dioxide's adsorption on Lewatit VP OC 1065® is now fully characterised, allowing for accurate process assessment as a benchmark direct air capture sorbent. Performance of new novel adsorbents, such as amine-functionalised metal-organic frameworks, can be compared to Lewatit VP OC 1065® to decide whether the adsorbent deserves further investigation.