The Hydrogen Reduction Behavior of MoO3 Powder

Abstract

, MoO3 → MoO2MoO2 → Mo. MoO3 30 vol% H270 vol% Ar. 550~600°C30~150. MoO2H2 , 700~750℃30~150.. 1,. 85.0 kJ/mol 9.18x10 7. ,. 2. MoO2→ Mo. , , 2, , Abstract The hydrogen reduction behavior of molybdenum oxides was studied using a horizontal-tube reactor. Reduction was carried out in two stages: MoO 3 → MoO 2 and MoO 2 → Mo. In the first stage, a mixed gas composed of 30 vol% H 2 and 70 vol% Ar was selected for the MoO 3 reduction because of its highly exothermic reaction. The temperature ranged from 550 to 600 °C, and the residence time ranged from 30 to 150 min. In the second step, pure H 2 gas was used for the MoO 2 reduction, and the temperature and residence time ranges were 700-750 °C and 30-150 min, respectively. The hydrogen reduction behavior of molybdenum oxides was found to be somewhat different between the two stages. For the first stage, a temperature dependence of the reaction rate was observed, and the best curve fittings were obtained with a surface reaction control mechanism, despite the presence of intermediate oxides under the conditions of this study. Based on this mechanism, the activation energy and pre-exponential were calculated as 85.0 kJ/mol and 9.18 × 10 7 , respectively. In addition, the pore size within a particle increases with the temperature and residence time. In the second stage, a temperature dependence of the reaction rate was also observed; however, the surface reaction control mechanism fit only the early part, which can be ascribed to the degradation of the oxide crystals by a volume change as the MoO 2 → Mo phase transformation proceeded in the later part.