PMID: 11322552Apr 27, 2001Paper

Unique structural properties of the Mg-Al hydrotalcite solid base catalyst: an in situ study using Mg and Al K-edge XAFS during calcination and rehydration

Chemistry : a European Journal
J A van BokhovenD C Koningsberger

Abstract

The changes in the layered structure of Mg-Al hydrotalcite (Mg/ Al = 2) during heat treatment have been investigated by using in situ XAFS simultaneously at the Mg and Al K-edges. The development of unique in situ instrumentation allowed the coordination environments at both the Mg and Al centers to be monitored as a function of the temperature and heat treatment. The results of this study show that the hydrotalcite structure is highly flexible, and should lead to the further development of hydrotalcites as new solid basic catalysts. Moreover, the Mg and Al cations in the cation layers show different behavior as a function of temperature. The coordination of some octahedral Al ions decreases already at a temperature of 425 K, whereas the coordination about Mg does not show any modification at this temperature. However, hydrotalcite treated at 425 K, followed by cooling down to room temperature resulted in a complete reversal to the original octahedral Al coordination. It is proposed that Al-OH bond breakage occurs at 425 K, without the evolution of H2O. This bond is restored after cooling to room temperature. The actual dehydroxylation of hydrotalcite commences between 425 and 475 K, as indicated by a change in coordination of ...Continue Reading

References

Jul 21, 2004·Journal of Synchrotron Radiation·J A van BokhovenD C Koningsberger
Jul 21, 2004·Journal of Synchrotron Radiation·C S DoyleG E Brown

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Citations

Oct 10, 2006·Chemistry : a European Journal·Javier Pérez-RamírezNiek M van der Pers
Mar 21, 2009·Chemistry : a European Journal·Damien P DebeckerGuido Busca
Apr 21, 2020·Dalton Transactions : an International Journal of Inorganic Chemistry·Mateusz DembowskiCarolyn I Pearce
Nov 4, 2016·Acta Crystallographica. Section A, Foundations and Advances·Svetlana CherepanovaVladimir Doronin
Dec 2, 2009·Langmuir : the ACS Journal of Surfaces and Colloids·Heriberto PfeifferJaime S Valente

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