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Local geometry of AlO4 and SiO4 tetrahedra in silicon rich (Si/Al 38) chabazite was investigated using 27Al 3Q and 29Si MAS NMR spectroscopy and QM-Pot calculations. We further studied the effects of (1) Al as nearest neighbor and (2) silanol “nest” on the SiO4 local geometry as well as 29Si NMR chemical shift. Silanol “nests” are a model of a defect (vacant T site after a dealumination) in a zeolite framework.

27 Al 3Q MAS NMR spectroscopy and DFT/MM calculations were employed to study the Al siting in eleven differently synthesized samples of the ZSM-5 zeolite. The results of our study reveal that the occupation of the distinguishable framework T sites by Al and the concentration of Al in these T sites are neither random nor controlled by a simple rule. They both depend on the conditions of the zeolite synthesis. We further found that at least 10 out of the 24 distinguishable framework T sites are occupied by Al in our ZSM-5 samples.

Metathesis catalysts based on Re(VII)oxide supported on organized mesoporous alumina (OMA) were characterized by a number of experimental techniques including X-ray diffraction (XRD), X-ray photoelectron (XPS), FTIR spectroscopy, MAS NMR, and nitrogen isotherms to understand the changes in textural and chemical properties during the activation and the metathesis reaction of olefins. The presence of pentacoordinated Al, population of acidic OH groups, concentration of Lewis acid sites and reducibility of Re (VII) oxide to Re(IV) species in OMA based catalysts – there are the main features, which were discussed in connection with catalytic activity.

Publisher Summary This chapter discusses aluminium (Al) distribution in high silica pentasil ring zeolites. Distribution of aluminium in the framework of ZSM-5 and Beta zeolites, represented by Al pairs and single Al atoms far distant from each other, is estimated from the distribution of divalent cobalt (Co) ions at the individual cationic sites and the changes in the concentration of hydroxyl (OH) groups and Lewis sites because of Co(II) exchange, as monitored by Fourier transform infrared spectroscopy (FTIR). The distribution of framework Al is not random, but it is affected by the concentration of aluminium and procedure of zeolite synthesis.

Publisher Summary This chapter discusses the characterization of aluminium (Al) and iron (Fe) sites in MCM-22, using adsorption of d 3 -acetonitrile, pyridine, and 2,6-di-tertbutylpyridine followed by Fourier transform infrared spectroscopy (FTIR) spectroscopy, sodium ion-exchange, and ultraviolet-visible (UV-Vis) spectroscopy of cobalt (Co 2+ ) ions located in cationic positions. The chapter also presents the detailed analysis of aluminium and iron distribution among single ions, ion pairs, Bronsted and Lewis sites, and internal and external surface.

Publisher Summary This chapter discusses the effect of the type of isomorphously substituted atoms (aluminum, iron, and boron) on the number of isolated heteroatoms, their pairs, and on the distribution of these pairs in the framework of ZSM-5 structure using the ultraviolet-visible (UV-Vis) spectroscopy of Co 2+ ions. The distribution of heteroatoms in the framework of ZSM-5 is not random and depends on the type and concentration of heteroatoms. The number of pairs of boron is significantly lower compared to the number of Al and Fe pairs for similar concentrations of heteroatoms. All Al, Fe, and B pairs are present in three different rings forming, thus, three different sites for divalent cations.