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The thermal decomposition of (NH4)4V2O11 in a nitrogen atmosphere and the kinetics of the first decomposition step

  • Inorganic Compounds
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Abstract

Although the reaction products are unstable at the reaction temperatures, at a heating rate of 2 deg·min−1 ammonium peroxo vanadate, (NH4)4V2O11, decomposes to (NH4)[VO (O2)2 (NH3)] (above 93°C); this in turn decomposes to (NH4) [VO3 (NH3)] (above 106°C) and then to ammonium metavanadate (above 145°C). On further heating vanadium pentoxide is formed above 320°C. The first decomposition reaction occurs in a single step and the Avrami-Erofeev equation withn=2 fits the decomposition data best. An activation energy of 148.8 kJ·mol−1 and a ln(A) value of 42.2 are calculated for this reaction by the isothermal analysis method. An average value of 144 kJ·mol−1 is calculated for the first decomposition reaction using the dynamic heating data and the transformation-degree dependence of temperature at different heating rates.

Zusammenfassung

Bei einer Aufheizgeschwindigkeit von 2 Grad/min zersetzt sich Ammoniumperoxovanadat (NH4)4V2O11 oberhalb 93°C zu (NH4)[VO(O2)2(NH3)], was sich oberhalb 106°C wiederum zu (NH4)[VO3(NH3)] und anschließend (oberhalb 145°C) zu Ammoniummetavanadat zersetzt. Bei weiterem Erhitzen wird oberhalb 320°C Vanadiumpentoxid gebildet. Die erste Zersetzung verläuft in einem einzigen Schritt, der durch die Avrami-Erofeyev-Gleichung mitn=2 am besten beschrieben wird. Bei isothermer Analysenmethode wurde für diese Reaktion eine Aktivierungsenergie von 148.8 kJ/mol und ein ln(A)-Wert von 42.2 berechnet. Unter Verwendung der dynamischen Aufheizdaten und der Konversionsabhängigkeit der Temperatur bei verschiedenen Aufheizgeschwindigkeiten wurde für die erste Zersetzungsreaktion ein mittlerer Wert von 144 kJ/mol berechnet.

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References

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  1. Department of Chemistry, University of Pretoria, 0002, Pretoria, South Africa

    C. A. Strydom

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  1. C. A. Strydom
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Strydom, C.A. The thermal decomposition of (NH4)4V2O11 in a nitrogen atmosphere and the kinetics of the first decomposition step. Journal of Thermal Analysis 40, 1069–1075 (1993). https://doi.org/10.1007/BF02546866

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  • DOI: https://doi.org/10.1007/BF02546866

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