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

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.