Thermal decomposition of ammonium paratungstate tetrahydrate: New insights by a combined thermal and kinetic analysis

• Thermal decomposition of APT·4H2O: A sequence of consecutive and competing reactions.
• Quantification of liberated water and ammonia from mass-spectrometric data.
• Stoichiometry of the entire decomposition pathway.
• Determination of activation energies of all thermal effects.

The thermal decomposition of ammonium paratungstate tetrahydrate has been studied in oxidising atmosphere at four heating rates employing the analytical techniques TG, DTG, DSC, and MS. In total, three endothermic and two exothermic effects have been detected. From the combined thermal and kinetic analysis based on the MS curves of water and ammonia, the decomposition path has been characterised as a system of consecutive and competing reactions. The activation energies of the five effects for water and ammonia were discussed. On the basis of the kinetic model and the quantified MS data the stoichiometry for the whole pathway of the thermal decomposition of the title compound was construed.

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