The formation of octahedral framework aluminum sites in acidic zeolite-depends on the adsorption of water. This could be shown by 27 Al MAS NMR spectroscopy under controlled atmosphere conditions. The 27 Al MAS NMR spectrum of the hydrated zeolite shows two lines corresponding to tetrahedral and octahedral Al sites, respectively. These NMR lines disappear on dehydrated samples. The adsorption of methanol or pyridine as probe molecules on the dehydrated zeolite samples restores only the tetrahedral (framework) aluminum sites in the 27 Al MAS NMR spectrum due to the relaxation of the distorted zeolite lattice by the adsorbed molecules. The acid-catalyzed reaction (470 K) of adsorbed methanol molecules on zeolite-, which supplies water, brings back the 27 Al MAS NMR signal caused by the octahedral framework aluminum sites.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.