Journal ArticleDOI
Thermal decomposition of hydrotalcites. An infrared and nuclear magnetic resonance spectroscopic study
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TLDR
The characteristics of hydrotalcite, following different stages of calcination, have been studied by means of thermogravimetric (TG), X-ray diffraction (XRD), IR, 1H and 27Al NMR techniques as discussed by the authors.Abstract:
Calcined hydrotalcites have been used extensively as catalysts for base-catalysed reactions. The calcination procedure in critical in determining the behaviour of the final material. The characteristics of the hydrotalcite, following the different stages of calcination, have been studied by means of thermogravimetric (TG), X-ray diffraction (XRD), IR, 1H and 27Al NMR techniques. We have shown that dehydroxylation begins within layers and then in a second stage occurs between adjacent layers, causing collapse of the structure. This process is accompanied by a change from octahedral to tetrahedral coordination of the aluminium. Decarbonation leads to the formation of micropores of radius <1.75 nm. Dehydroxylation and decarbonation are reversible processes, and their rates depend on the calcination temperature.read more
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Layered double hydroxides (LDH) intercalated with metal coordination compounds and oxometalates
TL;DR: In this paper, the synthesis, properties and applications of layered double hydroxides (LDHs) are reviewed, also known as anionic clays or hydrotalcite-like materials containing intercalated anions constituted by metal complexes or oxometalates.
Journal ArticleDOI
Oxidative dyhydrogenation of short chain alkanes on supported vanadium oxide catalysts
T. Blasco,J.M. López Nieto +1 more
TL;DR: In this article, the main data appeared in the last years on the oxidative dehydrogenation (ODH) of short chain alkanes on supported vanadium oxide catalysts, and it was concluded that tetrahedral V5+-species are active and selective sites in the ODH of C2-C4 alkanes.
Journal ArticleDOI
New Synthetic Routes to Hydrotalcite-Like Compounds − Characterisation and Properties of the Obtained Materials
TL;DR: In this paper, the effect of temperature of precipitation, total metal cations concentration, of the molar fraction M(III)/M(III) + M(II) in solution on the composition and on the crystallinity degree of the samples has been investigated.
Journal ArticleDOI
Mg/Al Ordering in Layered Double Hydroxides Revealed by Multinuclear NMR Spectroscopy
TL;DR: This work applied rapid (60 kilohertz) magic angle spinning to obtain high-resolution hydrogen-1 nuclear magnetic resonance (1H NMR) spectra and characterize the magnesium and aluminum distribution, showing that the cations are fully ordered for magnesium:aluminum ratios of 2:1 and that at lower aluminum content, a nonrandom distribution of cations persists.
Journal ArticleDOI
Gel nanostructure in alkali-activated binders based on slag and fly ash, and effects of accelerated carbonation
Susan A. Bernal,Susan A. Bernal,John L. Provis,John L. Provis,Brant Walkley,Rackel San Nicolas,John D. Gehman,David G. Brice,Adam R. Kilcullen,Peter Duxson,Jannie S.J. van Deventer +10 more
TL;DR: In this paper, two distinct gels (C-A-S-H and N-A−S−H) are formed in activated fly ash/slag blends, and under accelerated carbonation, the N−A −S −H gel behaves comparably to fly ash-based systems, while the C-A -S -H gel is decalcified similarly to alkali activated slag.
References
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The Infrared spectra of minerals
TL;DR: The use of vibrational spectroscopy as a tool in identifying mineral species and in deriving information concerning the structure, composition and reactions of minerals and mineral products is discussed in this paper.
Journal ArticleDOI
Catalytic Aluminas: Surface Models and Characterization of Surface Sites
Helmut Knözinger,Paul Ratnasamy +1 more
TL;DR: Aluminas have been used extensively as adsorbenu and active catalysrs and catalyst supponsm the pas as discussed by the authors, and they are used as catalysts for the larter process LS also caralyzed by molybdena-alumina.
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Anion-exchange properties of hydrotalcite-like compounds
TL;DR: Ion exchange isotherms between hydrotalcite-like (HT) ions were determined and the spacing and width of the 003 reflection were measured as a function of HT composition as mentioned in this paper.
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The Syntheses of Hydrotalcite-Like Compounds and Their Structures and Physico-Chemical Properties I: The Systems Mg2+-Al3+-NO3-, Mg2+-Al3+-Cl-, Mg2+-Al3+-ClO4-, Ni2+-Al3+-Cl- and Zn2+-Al3+-Cl-
TL;DR: The basic salts of this system were prepared and their structures and physico-chemical properties were studies by electron microscopy, chemical analysis, X-ray powder diffraction, thermal analysis, and acidity-basicity measurements as mentioned in this paper.
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Physico-chemical properties of synthetic hydrotalcites in relation to composition
TL;DR: Ahstraet et al. as discussed by the authors used coprecipitation followed by hydrothermal treatment between 150 ~ and 250~C. Based on the structural formula [Mgl_xAlx(OH)~lX+l(COz)x/2 �9 mH20] x-, pure solid solutions were formed in the range Al/(Al + Mg) = 0.2 to 0.33, where m = (1 - 3x/ 2).