(391e) Microscopic Transport in Mixtures of Ionic Liquids and Carbon Dioxide By NMR

Ionic liquids (ILs) show large sorption capacities for light gases such as carbon dioxide. This makes ILs highly attractive for potential applications as capture agents for carbon dioxide. Clearly, fundamental understanding of diffusion in mixtures of ILs and carbon dioxide is essential for an optimization of ILs for this application. Here we report results of diffusion studies of mixtures of selected ILs and carbon dioxide using pulsed field gradient (PFG) NMR technique at high magnetic field and high magnetic field gradients. This technique allowed obtaining first records of self-diffusivities of carbon dioxide inside ILs by any type of microscopic technique. Application of PFG NMR to a so-called “task specific” ionic liquid that chemically complexes with carbon dioxide resulted in the observation of an influence of exchange between the physisorbed and chemisorbed states of CO2 on diffusion in the mixtures of this IL and carbon dioxide. Exchange NMR was applied in combination with PFG NMR to quantify this chemical exchange process on the millisecond time scale.  In addition to diffusion of carbon dioxide, also ion diffusion was investigated by PFG NMR in the same mixtures.