Comparative electron spectroscopy for chemical analysis and nuclear magnetic resonance analysis of high-surface area materials: zeolites
✍ Scribed by T.L. Barr
- Publisher
- Elsevier Science
- Year
- 1995
- Tongue
- English
- Weight
- 536 KB
- Volume
- 3
- Category
- Article
- ISSN
- 0927-6513
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✦ Synopsis
In adsorption and catalytic technology, it is often suggested that many key high-surface area materials, e.g. zeolites, are "all surface". Despite this contention numerous examples have recently been found employing comparative solidstate magic-angle spinning nuclear magnetic resonance (MAS NMR; bulk analysis) and electron spectroscopy for chemical analysis (ESCA; surface analysis) that challenge this claim. Thus, for example, during the cor~version of certain Y zeolites to the ultrastable form, certain cation by-products have been found, by ESCA, to be selectively transported to the outer surface. In addition, during practical use many zeolites are often bound by select aluminas or clays to enhance their stability. ESCA analysis has demonstrated that these binders often coat most of the zeolite particles with a thin binder layer that is not detected by NMR. In some cases, these coatings are found to alter various aspects of the adsorptive and catalytic properties of these systems. In other cases NMR and ESCA results suggest detection of the same species. This report describes our present understanding of several key cases.