Thermal decomposition of the layered double hydroxides of formula Cu6Al2(OH)16CO3 and Zn6Al2(OH)16CO3 |
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| Authors: | N Voyer A Soisnard Sara J Palmer W N Martens and R L Frost |
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| Institution: | (1) Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, 2 George Street, Brisbane, GPO Box 2434, Queensland, 4001, Australia;(2) ENSICEN, Ecole Nationale Supérieure d’Ingénieurs et Centre de Recherche, 6 Boulevard Maréchal Juin, 14050 Caen Cedex, France |
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| Abstract: | Zn-Al hydrotalcites and Cu-Al hydrotalcites were synthesised by coprecipitation method and analysed by X-ray diffraction (XRD)
and thermal analysis coupled with mass spectroscopy. These methods provide a measure of the thermal stability of the hydrotalcite.
The XRD patterns demonstrate similar patterns to that of the reference patterns but present impurities attributed to Zn(OH)2 and Cu(OH)2. The analysis shows that the d003 peak for the Zn-Al hydrotalcite gives a spacing in the interlayer of 7.59 ? and the estimation
of the particle size by using the Debye-Scherrer equation and the width of the d003 peak is 590 ?. In the case of the Cu-Al
hydrotalcite, the d003 spacing is 7.57 ? and the size of the diffracting particles was determined to be 225 ?.
The thermal decomposition steps can be broken down into 4 sections for both of these hydrotalcites. The first step decomposition
below 100°C is caused by the dehydration of some water absorbed. The second stage shows two major steps attributed to the
dehydroxylation of the hydrotalcite. In the next stage, the gas CO2 is liberated over a temperature range of 150°C. The last reactions occur over 400°C and involved CO2 evolution in the decomposition of the compounds produced during the dehydroxylation of the hydrotalcite. |
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| Keywords: | dehydration dehydroxylation hydrotalcite thermal stability thermogravimetric analysis |
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