(511e) Kinetic and Mechanistic Study of the MoO2 Reduction to Mo2C in Methane Under Pulse-Type Conditions

Molybdenum carbide (Mo₂C), an interstitial transition metal carbide, has been widely used as an advanced material in myriad industrial applications due to its exceptional properties. These include its refractory nature, extreme hardness and strength, and high electrical and thermal conductivity. It also possesses catalytic activity for many chemical processes such as hydrogenation, reforming, water-gas shift and the Fisher-Tropsch reaction with a unique noble metal-like behavior. Solid state reduction between graphitic carbon and molybdenum oxides is commonly employed to produce Mo₂C. However, this carbothermic reaction involves very high temperatures (>1000 °C), leading to a low specific surface area, which is detrimental to catalytic purposes. New synthesis methods have been established to address this concern, such as the carburization reaction of molybdenum oxides with a flowing gas stream. This method yields the metal carbide with a specific surface area up to 200 m²/g.  Therefore, the present work investigates the kinetics of the formation of Mo₂C using a molybdenum dioxide (MoO₂) precursor and methane as the carburizing agent. Moreover, the carburization of transition metal oxides usually undergoes a single step directly to the carbide form, but in the case of MoO₂, transient X-Ray diffraction (XRD) indicates the formation of molybdenum metal as an intermediate species. In order to elucidate this particular reaction mechanism, thermogravimetric analysis, XRD and electron microscopy techniques have been employed. This mechanism was studied under pulse conditions wherein a cyclic flow of CH₄ was reacted with a packed bed of MoO₂.