Titanium-substituted zeolites and molecular sieves investigated by NMR

Article Abstract:

The nature of titanium sites in titanium-substituted zeolites were examined using the paramagnetism of Ti3+.

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Chemical shift prediction in the 29Si MAS NMR of titanosilicates

Article Abstract:

The chemical shifts of titanosilicates were observed using 29Si MAS nuclear magnetic resonance to determine the existence of interactions between titanium silicates. The study tried to identify the catalytically active site in titanium-substituted zeolites. It was also hypothesized that the 29Si isotropic chemical shift relied on both the substitution and geometry of Si-O-X bonds. It was concluded that even if the equations and correlations were used in the study, there was still an unclear knowledge on the 29Si MAS NMR spectrum of the titanium-containing zeolites.

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Temperature dependence of nuclear magnetic resonance chemical shifts of 129Xe in the alpha-cages of NaY zeolite

Article Abstract:

One- and two-dimensional NMR spectra of 129Xe sorbed in NaY zeolite at a loading of about 1 Xe atom/4 alpha-cages were investigated as a function of temperature. The data were fitted to the simple statistical mechanical cylindrical pore model of Cheung producing a van der Waals adsorption energy of 3.3 kJ/mol. Two-dimensional data indicated that the intercrystalline diffusion is slow compared to intracrystalline diffusion. Findings showed that the Xe atoms spend most of their time in the alpha-cages and at the lower temperatures, near the cage walls.

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