SCHEDULED MAINTENANCE
Reversible thermal behaviour of layered double hydroxides:a thermogravimetric study
Abstract
Layered double hydroxides (LDHs) of Mg with trivalent cations such as
Al, Cr and Fe show two mass loss steps on heating; the low-temperature
(25–250 °C) loss is due to dehydration and the high-temperature
(250–450 °C) loss is due to decomposition. Both steps are
reversible and the oxide residues obtained after calcination at 700 °C
reconstruct back to the hydroxide phase. On the other hand the LDHs of Ca
and Ni dehydrate reversibly but their decomposition reaction is
irreversible. The LDHs of Zn and Co lose mass continuously up to 700
°C without any well resolved steps and the loss is irreversible. These
results have implications on the synthesis of selective catalysts by
calcination of LDHs.
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