Investigation on the Kinetics and Mechanism of Aluminothermic Reduction of Molybdenum Trioxide: Non-isothermal Kinetics

In this work, effect of milling process and CaO addition on the reaction mechanism and kinetics of aluminothermic reduction of molybdenum trioxide were studied by simultaneous thermal analysis, differential scanning calorimetry, X-ray diffraction analysis and Coats–Redfern method, respectively. For this purpose, molybdenum trioxide was reduced by Al powder under two different conditions of mechanical activation by milling process and as received form mixed by stoichiometric amount of CaO that was required for creation of CaMoO 4 intermediate phase. In the case of using milled molybdenum trioxide, 20 wt% of aluminum oxide was used as heat absorber. The results showed that by using mechanically activated MoO 3 , the reduction reactions proceeded through the formation of intermediate phases of Al 2 (MoO 4 ) 3 and MoO 2 . In the presence of CaO, the intermediate phase was changed to CaMoO 4 . In both cases, the reaction temperatures and their activation energies decreased. The kinetic model for the aluminothermic reduction of un-milled and milled molybdenum trioxide was determined as chemical control, where by addition of CaO, mechanism of the reduction reaction was changed to diffusion control.