Agglomeration during reduction of MoO3

Molybdenum powder is manufactured in a two step process starting from MoO₃. The first step reduction of MoO₃ to MoO₂ is carried out in rotary calciners. Agglomeration of powder occurs during this reduction stage resulting in several manufacturing issues. The evolution of agglomeration during the reduction of MoO₃ was investigated in the current study. As-received MoO₃ and MoO₃ milled for 0.5 h were used as the starting powders. The powders were reduced at 550 °C, 650 °C and 750 °C in a hydrogen atmosphere. The starting and reduced powders at various temperatures were analyzed using BET surface area, XRD, and SEM techniques. The surface area of the reduced powders was monitored for quantifying the degree of agglomeration. The surface area was found to be minimum for the samples reduced at 650 °C. SEM observations confirmed the agglomeration of powders during reduction process. XRD analysis showed complete reduction of MoO₃ to MoO₂ at 650 °C and 750 °C. The agglomeration of the powders was either due to melting of eutectic formed between MoO₃ and Mo₄O₁₁ or due to partial melting of MoO₃. The reduction of MoO₃ is recommended to be completed at a low temperature to prevent agglomeration of the oxide powders.