Preparation and mechanism of molybdenum trioxide by microwave oxidation roasting of molybdenite

In order to explore the optimal process and oxidation roasting mechanism of preparing micron grade molybdenum trioxide by microwave roasting molybdenite, the roasting thermodynamics, high temperature microwave absorption characteristics and roasting process of molybdenite were analyzed. The experimental results show that molybdenite is an efficient microwave absorbing ore, and MoS2 is the main microwave absorbing mineral, while Al2O3, SiO2 and other gangues hardly absorb microwave. The effects of microwave roasting temperature, roasting time and air flow rate on the product of molybdenum trioxide are obtained. Increasing roasting temperature, roasting time and air flow rate are conductive to improve the conversion of molybdenum. When the roasting temperature and time are further increased, some MoO3 crystals volatilized and the Mo content is reduced. The optimized process conditions of microwave roasting are as follows: roasting temperature of 700 ℃, roasting time of 100 min and air flow rate of 0.3 m3/h. Various forms of nano-MoO3 crystal materials can be directly prepared by microwave oxidation roasting of molybdenite, showing nano-sheet, needle-like and banded high-purity molybdenum trioxide. The microwave oxidation roasting process is divided into three stages, the first stage: molybdenite is dried and dissociated, and some impurities were oxidized; the second stage: the reaction rate of MoS2 oxidation to MoO3 is fast at first and then slow, and a large amount of heat is released; the third stage: partial MoO3 is volatilized, residual MoO3 reacts with impurity oxides to form molybdate, and the product is sintered. © 2023 Central South University of Technology. All rights reserved.