NMR Revealed Water-Oxide Interaction

Slurry system is used in a wide range of processes of both chemical and biochemical industries, especially in heterogeneous catalysis. The slurry reaction system shows excellent reaction behavior. Obviously, it would be very helpful if one can understand the behavior of the slurry system at molecular level. In this thesis, the oxide - water slurry system is chosen as object of research in order to observe their interaction through chemical shift and spin-lattice relation time changes as the ratio of solid - liquid varies, hoping to shed some light on the behavior of the liquid in slurry systems at molecular level. The results are: (1) The water-alumina interaction was studied using high-resolution 1H NMR. The spin-lattice relaxation times (T1) were obtained. The results of T1 indicate that there exit three states of water in water-alumina system, e.g., bound water, pore water and bulk water. The chemical shift (8H) decreases when the concentration of water by weight increases due to the different contributions of the three states of water in samples. The H NMR variable temperature measurements of water in slurry sample (the concentration of water by weight, 28.5%) reveals that the H value for adsorbed water decreases nearly linearly with elevating temperature while T1 increases with elevating temperature; (2) The water-nano-sized anatase titania and water-nano-sized rutile titania interaction were also studied using high-resolution 1H NMR. The spin-lattice relaxation times (T1) were obtained. The results of T1 indicate that there exit two states of water, e.g., bound water and bulk water. The chemical shift (H) decreases when the concentration of water by weight increases duo to the different contributions of the two states of water in samples. There are differences of the H value and the spin-lattice relaxation times (T1) in water-anatase titania and water-rutile titania samples due to the differences in crystal structure and the states of surface. The 1H NMR variable temperature measurements of water in slurry sample (concentration of water by weight, 25%) reveals that the H value for adsorbed water decreases nearly linearly with elevating temperature and T1 increases with elevating temperature.