Tungsten Oxide Hydrogen Reduction Principle

Tungsten oxide hydrogen reduction is one of the methods of reducing tungsten oxide with hydrogen at high temperatures to produce tungsten powder. Compared with other methods such as carbon reduction and zinc reduction, the tungsten oxide hydrogen reduction method has higher purity and easier product property control. Hydrogen reduction method is a widely used and effective method in the field of metal powder production such as tungsten.

Under normal conditions, the tungsten oxide hydrogen reduction process consists of a diffusion step and a crystallization chemistry. It belongs to the adsorption - autocatalytic reaction process, for the gas - solid two different phase reaction type. Hydrogen gas will adsorb on the tungsten oxide surface before the lattice of tungsten oxide changes. The oxygen on the surface of the tungsten oxide is then chemically reduced with hydrogen. As the hydrogen reduction reaction progresses, the hydrogen reduction reaction slowly penetrates into the tungsten oxide interior. The final tungsten oxide lattice type changes to the metal tungsten lattice type. This type of lattice transition is called the crystallization chemistry. The water vapor generated by this chemical reaction will be desorbed out, the reduction reaction process can be expressed by the following equation:

This hydrogen reduction mechanism known as adsorption - autocatalytic mechanism, it can be divided into three periods: incubation period, autocatalytic period and deceleration period. And this adsorption - autocatalytic mechanism belongs to chemical adsorption, refers to the chemical reaction between hydrogen and tungsten oxide, the formation of chemical bonding caused by adsorption. In the adsorption process not only gravity, but also the force of the chemical bond, so the adsorption energy larger. To expel the adsorbed material requires a higher temperature, and even if the adsorbed material is expelled, a chemical change has taken place, no longer the original material, and the general catalyst functions in this manner.

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