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Characterization studies of metal containing Y-type zeolites
Abstract
Crystallite aggregates of Na-Y, Ba-Y, Ca-Y, Fe-Y, and Ru-Y zeolites have been studied via $\sp{129}$Xe NMR spectroscopy. The response of the $\sp{129}$Xe resonance of adsorbed xenon depends upon the aggregate size. Both the chemical shift and the linewidth of the resonance display a large aggregate size dependence for Ca-Y, Fe-Y, and Ru-Y zeolites. Differences in linewidths are observed in Ba-Y and Na-Y zeolites. Samples made by mixing Ru-Y zeolite with Na-Y exhibit a motional narrowing, which also depends upon aggregate size. A packing dependence is observed in samples of Fe-Y and in mixed samples containing both Ru-Y and Na-Y. These results are consistent with a model in which xenon migrates over many zeolite crystallites on the NMR timescale. The aggregate size effects are attributed to intercrystalline diffusion and residence of xenon atoms in the mesopore structure occurring at aggregate grain boundaries. $\sp{27}$Al and $\sp{29}$Si magic angle spinning (MAS) NMR studies of Ru-Y zeolite reveal that impregnation of the zeolite with RuCl$\sb3$ causes dealumination of the lattice. The loss of crystallinity is apparently not caused by the low pH of the exchange solution. NaCl treatment of the Ru-Y produces materials with very high percentages of ruthenium by weight. Little structural damage is observed upon low temperature reduction of Ru-Y. However reductions performed at 723 K cause sintering and the formation of large clusters of Ru on the outer edges of the crystallites. Large RuO$\sb2$ particles are formed under oxidizing conditions. $\sp{129}$Xe NMR has been used to characterize the reaction of Mo(CO)$\sb6$ in Na-Y zeolite. The adsorption of Mo(CO)$\sb6$ results in a concentration gradient of Mo species down the length of the NMR tube. Enhanced xenon adsorption is observed after molybdenum subcarbonyl species are formed. Fully decarbonylated molybdenum species are mobile in the presence of oxygen and move to positions inside the sodalite cages and/or hexagonal prisms.
Subject Area
Chemistry|Chemistry
Recommended Citation
Tway, Cathy L, "Characterization studies of metal containing Y-type zeolites" (1992). ETD collection for University of Nebraska-Lincoln. AAI9225498.
https://digitalcommons.unl.edu/dissertations/AAI9225498