Anna Karina MÜLLER1, Jost HEISE1, Barbara KIRCHNER1
1University of Bonn, Bonn, Germany
One of the main factors in the current global climate changes is the increasing CO2 emissions, which has led to a great interest from scientist in finding sustainable solutions to overcome this problem. One approach is to capture the CO2 in a solution. Thus, the potential application of ionic liquids (ILs) and specifically amino acid ionic liquids (AAILs) as carbon dioxide absorbents was studied.
In the investigated ILs two different absorption behaviors could be detected, the chemical absorption, where the CO2 interacts strongly with the anion of the IL, and the physical absorption, where the CO2 depicts a weak interaction with it. It was shown that the absorption capacities of unmodified ILs are too low for the application as CO2 absorbents under normal conditions, whereas AAILs depict higher CO2 absorption rates if compared to the other ILs or pure amino acids.
We continued investigating this application of ILs with added pressure to the system using density functional theory (DFT) methods. Applying pressure could have a significant influence on the absorption capacity as well as the interaction between the IL and CO2. Thus, in this study we compared different ILs and their ability to absorb CO2 under normal conditions and under pressure. To reproduce the effects that pressure has on the investigated systems, DFT calculations that simulate hydrostatic pressure were performed. The essence of the performed analyses was comparing the different values for the reaction energies as well as the reaction barriers of the absorption process. Moreover, the change in geometry of the systems under pressure, with an emphasis on the structure of the transition states, was one of the main focusses of this work. The aim of this study was to investigate the general influence pressure has on the ability of different ILs to absorb CO2 and explore the question if the application of pressure can make the process more sustainable and effective.