Stepwise Reduction Behavior of Molybdenum Trioxide Using Ammonia Gas

Ammonia recovered as a by-product of the metallic molybdenum production process was reused as a reducing agent for molybdenum trioxide (MoO 3 ), and its stepwise reduction behavior was investigated.During the reduction of MoO 3 to molybdenum dioxide (MoO 2 ), a conversion of 99.99% was achieved at 525°C for 30 min with an ammonia flow rate above 0.15 L/min, and XRD and SEM-EDS analyses confirmed the formation of pure MoO 2 .In the subsequent reduction of MoO 2 to metallic Mo, an NH 3 -Ar mixed gas alone yielded limited conversions of 65.62-75.97%at 700-725°C because of the formation of molybdenum nitride (Mo 4 N 7 ) from nitrogen generated during ammonia decomposition.Introducing hydrogen into the gas mixture suppressed nitride formation, increasing the conversion to 99.81% at 800°C after 120 min, with XRD analysis confirming the formation of pure metallic Mo.These results demonstrate that ammonia volatilized during calcination can be effectively reused as a reducing agent, thereby improving process efficiency and reducing hydrogen consumption.