抄録
The equilibrium decomposition pressures of vanadium (IV) oxide sulfate (VOSO4) and the related thermodynamic data of thermal decompositions have been determined by a transpiration method and an electrochemical method using a ZrO2-CaO solid electrolyte.
The Gibbs energies for the reaction:
2VOSO4=V2O5+SO2+SO3 (1)
can be expressed by
ΔG°=329.1+0.36T(kJ) (680-863K).
Also the Gibbs energies for the reaction:
VOSO4=1/2V2O4+SO3 (2)
can be expressed by
ΔG°=204.2-0.21T(kJ) (843-863K).
Further, based upon the equilibrium decomposition pressure data for the thermal decompositions as mentioned above, SO2, SO3 and O2 partial pressure dependence on the decomposition reaction rate have been investigated by an isothermal weight-change determination method varing the atmosphere. The reaction (1) in 1atm N2 and SO2-SO3-N2 (490-520°C), and O2-N2 (450-500°C) atmospheres was explained by a contracting cube model kinetic equation and both SO2-SO3 and O2 partial pressure dependence were clearly obtained. The reaction (2) in 1atm SO2 atmosphere (570-591°C) was explained by Avrami-Erofeev kinetic equation. The activation energies were also discussed.
