Tungsten Oxide in The Hydrogen Reduction Process at Different Periods of Changes

The reaction principle of tungsten oxide hydrogen reduction process is adsorption-autocatalytic mechanism. Adsorption - autocatalytic mechanism is a hydrogen pass into the tungsten oxide products, hydrogen and tungsten oxide full contact, the reaction, after the tungsten oxide adsorption from the surface to its internal autocatalytic reaction. As the hydrogen adsorption proceeds, the interior of the tungsten oxide is reduced by hydrogen to change its structure and generate new species.

Adsorption - autocatalytic mechanism can be divided into three periods, namely the incubation period, since the catalytic period and reducer.

(1) Incubation period: Hydrogen adsorption on the tungsten oxide surface, and tungsten oxide surface active role. That is, in the lattice of hydrogen and tungsten oxide, the chemical reduction reaction occurs between the two by combining the unsolvable particles for some reason.
(2) Autocatalytic phase: Hydrogen reduction of tungsten oxide to obtain the product of metal tungsten, tungsten oxide and the product of the phase interface of tungsten is increasing. At the same time, the contact surface between the tungsten oxide and the new phase crystallite produced at the active part of the incubation period is also increased, resulting in distortion and defects of the crystal lattice of the tungsten oxide. Hydrogen molecules adsorbed on the surface of tungsten oxide are likely to decompose into highly active hydrogen atoms. These processes will reduce the activation energy of the reaction and thus accelerate the chemical reaction process, that is, the role of autocatalytic. With the new phase of the core as the core gradually expanded to its periphery, so that crystallization of chemical reactions.
(3) Deceleration period: Each crystal nucleation reaction zone developed into a reaction zone, the surface area of which will gradually decrease as the reduction process proceeds, so that the overall reaction rate is gradually reduced. This reaction period is called the deceleration period.

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