DTA/TGA study of molybdenum oxide reduction by Mg/Zn & Mg/C combined reducers at non-isothermal conditions

Abstract In this work the reduction mechanisms of molybdenum oxide by single (Mg, Zn, C) and complex (Mg/C, Mg/Zn) reducers are reported. It is revealed that in the case of Mg and Zn the reduction undergoes before Mg/Zn melting, i.e. by solid-state mechanism. Unlike these systems, in the case of carbon, a stepwise reduction takes place. First stage ( 3  → MoO 2 reaction; next one is endothermic reduction (> 900 °C) of MoO 2 to the mixture of Mo and Mo 2 C. When combined reducer is used, such as Zn/Mg, then before reduction process the Zn melts and reduction takes place by liquid–solid mechanism. In this case apart MoO 2 (and MgO ∗ MoO 2 ) MgZn 2 also is formed. When the MoO 3 is reduced by Mg/C mixture, the reduction process starts by carbon at 520–650 °C forming MoO 2 . Next the Mg melts and molten Mg reduces MoO 2 yielding Mo. Based on the results obtained by DTA/TGA investigations the effective activation energy values are calculated for reduction stages for all studied mixtures.