Synthesis, characterization and combined kinetic analysis of thermal decomposition of hydrotalcite (Mg6Al2(OH)(16)CO3 center dot 4H(2)O)

摘要

Here, a kinetic study of the thermal decomposition of synthesized hydrotalcite, Mg-6 Al-2 CO3(OH)(16)center dot H2O, has been carried out using thermogravimetric experiments in air atmosphere. It is shown that the thermal decomposition occurs in two well differentiated stages. The first one is a single-step dehydration process that comprises the release of four water molecules. On the other hand, the second stage is complex and corresponds to both dehydroxylation and decarbonation processes which occur simultaneously. The kinetic parameters describing all processes were calculated by means of a combined approach comprising isoconversional, model-fitting and deconvolution methods. It was concluded that dehydroxilation and decarbonization cannot be separated by TG experiments and the two stages contributing to the complex process do not apparently match the expected stoichiometry of the process. Therefore, it is proposed that such stages mark a change on the reaction mechanism due to the structural collapse of the laminar double hydroxide.