17O NMR Studies of Low Silicate Zeolites

17O DOR and other solid-state NMR studies concerning the basic properties of zeolites LSX

“…In a previous study [10] we obtained from all 17 Table 2, in order to obtain the intrinsic isotropic chemical shift. The 122-MHzspectrum in Fig.…”

“…We obtained a maximum loading of one pyrrole and two formic acid molecules per cavity (1/8 unit cell). 1 H MAS NMR spectroscopy shows that the molecules undergo a chemical reaction for higher loadings, which were used in previous studies [10].…”

“…After publishing the first 17 O NMR results concerning the basicity of the zeolite LSX [10] we became aware that the chemical stability of an ion exchanged and 17 O enriched zeolite LSX during activation (dehydration under vacuum) and loading (with acid molecules) is a crucial point [11]. We improved the ion exchange procedure for the zeolites, changed the 17 O enrichment method and limited strongly the quantity of zeolites and acid molecules [11].…”

“…We apply DOR for measuring the 17 O NMR spectra in the present study, since it completely averages out second-order quadrupolar broadenings and gives a higher resolution than 3QMAS NMR spectroscopy [10].…”

High resolution 17O MAS and triple-quantum MAS NMR studies of gallosilicate glasses

“…Ab initio calculations have, for example, predicted d iso decreases with increasing T-O-T bond angles [62][63][64][65]. Experimental studies of some crystalline molecular sieves concluded that d iso of oxygen at different crystallographic sites does decrease linearly with increasing Si-O-Al bond angle [66][67][68][69]. However, it has also been demonstrated that the cation in the first coordination shell has a large impact on d iso [68,70,71].…”