Transport properties of mixtures of carbon dioxide and ionic liquids by NMR

This work presents results of microscopic experimental studies of diffusion in mixtures of ionic liquids and carbon dioxide. Such studies are important for the development of fundamental knowledge of transport properties of these mixtures which can potentially find applications in carbon dioxide capture and separations. Chapter 3 focuses on mixtures of imidazolium-based ionic liquid and carbon dioxide and mixtures of an amine-functionalized ionic liquid and carbon dioxide. Chapter 4 discusses results obtained with pure imidazolium-based ionic liquid and its mixtures with carbon dioxide confined in mesoporous silica with well-defined pore system. Studies of confinement effects become increasingly more important due to development of novel materials such as supported ionic liquid membranes (SILMs).;The studies were performed by a novel multinuclear pulsed field gradient (PFG) NMR technique, which combines the advantages of a high magnetic field (17.6 T) and a high magnetic field gradient (up to 30 T/m). For the studied imidazolium-based ionic liquid the self-diffusion coefficients of carbon dioxide were found to be approximately an order of magnitude larger than the corresponding self-diffusion coefficients of the ions. It was observed that an increase in temperature and in the amount of carbon dioxide in the ionic liquid lead to an increase in the ion self-diffusivities without changing the relationship between the self-diffusion coefficients of the cations and anions.;NMR exchange spectroscopy (EXSY) and NMR diffusion spectroscopy (PFG NMR) were applied to investigate self-diffusion in a mixture of carbon dioxide and an amine-functionalized ionic liquid under conditions of an exchange of carbon dioxide molecules between the reacted and unreacted states in the mixture. Analytical treatment of the data enabled determination of diffusivities of carbon dioxide in the reacted and unreacted states.;Diffusion NMR was used to study the diffusion of a mixture of the ionic liquid and carbon dioxide confined in porous silica. It was observed that carbon dioxide self-diffusion in the confined mixture can be at least as fast as in the bulk mixture even under conditions when the confinement effects appreciably reduce the ion diffusivity.