Hostname: page-component-7c8c6479df-5xszh Total loading time: 0 Render date: 2024-03-29T07:35:00.863Z Has data issue: false hasContentIssue false

Aluminas Rehydration and Dehydration

Published online by Cambridge University Press:  10 February 2011

J. J. Fripiat*
Affiliation:
Department of Chemistry and Laboratory for Surface Studies, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201
Get access

Abstract

In this review paper, results on the A12O3-water interactions will be critically examined. The synthesis of alumina precursors rich in structural defects can be operated in an aqueous solution containing ligands with high affinity for A13+aq or by restricted hydrolysis of Al-alkoxides. Calcination of the gels yields transition aluminas containing four (IV), five (V) and six (VI) fold coordinated aluminum. The pore-size distribution, the Alv content and the degree of crystallinity are controlled by the degree of condensation of the oligomer species in the gel. In a dehydrated alumina two kinds of AlIV with isotropic chemical shifts at ∼73 and 58 ppm, respectively, are present. The distorted AlIV (chemical shift at 58 ppm) and Alv are surface species. Upon water chemisorption the distorted AlIV line disappears while the Alvline is reinforced. As bulk rehydration progresses the Alv line intensity decreases. It is only partially restored upon recalcination. Thus, hydration-rehydration cycles cure the solid from its defects and increase crystallinity. The onset of rehydration is the chemisorption of water on the surface Lewis sites just as Lewis sites result from a thorough dehydration.

Type
Research Article
Copyright
Copyright © Materials Research Society 1997

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

1. Brinker, C. J. and Scherer, C. W, Sol-Gel Science (Academic Press, New York, 1990).Google Scholar
2. Wood, T. E., Siedle, A. R., Hill, J. R., Skarfune, R. P., and Goodbrake, C. J., Mater. Res. Symp. V110, 97 (1990).Google Scholar
3. CRC Handbook of Chemistry and Physics, 52nd Edt., (The Chemical Reader Co., Cleveland Ohio, 19711972).Google Scholar
4. Paramzin, J. M., Zolotowski, B. P., Krivoruchko, O. P., and Buyanov, R. A., Proc. VI Intern. Symp. Heterogeneous Catal.s, Part 2, 369 (1987).Google Scholar
5. Chen, F. R., Davis, J. G., and Fripiat, J. J., J. Catal. 133, 263 (1992).Google Scholar
6. Coster, D. J. and Fripiat, J. J., Chem. Mater. 5, 1204 (1993).Google Scholar
7. Gruver, V. and Fripiat, J. J., J. Phys. Chem. 98, 8549 (1994).Google Scholar
8. Coster, D. J., Blumenfeld, A. L., and Fripiat, J. J., J. Phys Chem. 98, 6201 (1994).Google Scholar
9. Coster, D. J., Gruver, V., Blumenfeld, A., and Fripiat, J. J., Mat. Res. Soc. Symp. 351, 961 (1994).Google Scholar
10. Blumenfeld, A. L. and Fripiat, J. J., ”Acid Sites Topology in Aluminas and Zeolites from High-Resolution Solid-State NMR,” in Topics in Catalysis, submitted (1996).Google Scholar
11. Coster, D. J., Levitz, P., and Fripiat, J. J., Mater. Res. Symp. V351, 157 (1994).Google Scholar
12. Blumenfeld, A. L., Coster, D. J., and Fripiat, J. J., Chem. Phys. Lett. 231, 491 (1994).Google Scholar
13. Coster, D. J., Fripiat, J. J., Muscas, M., and Auroux, A., Langmuir 11, 2615 (1995).Google Scholar
14. Auroux, A., “Catalysis by Aluminas and Zeolites,” Topics in Catalysis, submitted (1996).Google Scholar
15. Knözinger, H. and Ratnasamy, P., Catal. Rev. Sci. Engin. 17, 31 (1978).Google Scholar
16. Frost, D. C., Herring, F. G., McDowel, C. A., Mustafa, M. R., and Sandha, J. S., Chem. Phys. Lett. 2, 663 (1968).Google Scholar
17. Al-Jabouty, M. I. and Turner, D. W., J. Chem. Soc., 4434 (1964).Google Scholar