Abstract
The oxidation mechanism of a commercial molybdenum concentrate was investigated up to 650 °C using thermal analysis. Upon introduction of air, the molybdenite concentrate started to lose mass due to the oxidation of MoS2 to form molybdenum oxide and SO2. After a rapid mass loss, this was followed by a period of mass gain due to the oxidation of MoO2 to MoO3. The solid-state reaction between MoS2 and MoO3 to form MoO2 was also found to take place. Initially, as air is introduced, the rate is controlled by gas-phase diffusion of oxygen to the reaction surface. With time, as the surfaces of the MoS2 particles become oxidized and the rates start to slow, MoO3 starts to form. This generally leads to a mass gain as well as a slow down in oxidation rate due to the formation of a fairly dense MoO3 product layer. The timing of the various reactions was very dependent on the actual experimental conditions such as sample mass, gas flow rate, and heating rates.
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