Ammonium Tetrathiotungstate Producing Process

Ammonium tetrathiotungstate is widely used in the synthesis of the biological nitrogen-fixation enzyme activity center-tungsten iron-sulfur atom cluster compound. 

It is also a precursor of coal liquefaction and heavy oil hydrogenation catalyst, and can be used as raw material for the preparation of load and non-load tungsten sulfide hydrogenation catalysts, next generation transistor, double-layer capacitor, optical electrochemical solar cells, electrochemical sensors, hydrogen storage materials and electrode materials. Therefore, it is of great significance to develop a high-yield producing process of ammonium tetrathiotungstate.

Some scholars have proposed that achieving a simple preparation process, environmentally friendly, high yield quantity, easy to industrialize ammonium tetrathiotungstate, can be produced by tungstate or tungsten trioxide and ammonium sulfide solution reaction. In the reaction process, by vacuum or injecting inert gas into the reaction fluid in the way the reaction process can release ammonium gas to promote the reaction equilibrium move to the direction of ammonium tetrathiotungstate, and add the appropriate amount of ammonium salt to the reaction solution, promote the precipitation of the product of ammonium tungstate to improve the yield of high-purity ammonium tetrathiotungstate. The reaction is shown in the following formula:

For example, add ammonium sulfide solution with 8% sulfide content into flask. Then add 122.3g sodium tungstate and inject argon during reaction process. Heat the temperature to 100℃, mix for 0.5h, add 427g ammonium bisulfate, put still and crystallization for 24 hours. Then suction filtration with buchner funnel and wash crystallization with distilled water(3 ×100mL) and ethanol(3 ×100mL) for three times. Dry for 8 hours under room temperature and can get yellow needle shape crystalline 126.6g, output rate is 98% (calculated by sodium tungstate).

The ammonia gas generated in the reaction process is discharged from the reaction liquid by directly using a reaction solution of tungstate or tungsten trioxide with an ammonium sulfide solution, vacuuming the reaction process, or bubbling nitrogen or an inert gas into the reaction liquid. The reaction equilibrium shifts toward the product ammonium tetrathiotungstate, and an appropriate amount of ammonium salt is added to the reaction liquid to promote the precipitation of the product ammonium tetrathiotungstate to obtain high purity ammonium tetrathiotungstate. The method has the advantages of less waste discharge, no need to use irritating ammonia water and highly toxic and odorous hydrogen sulfide gas, simple process conditions, environmental friendliness and yield of up to 98%. The purity of the ammonium tetrathiotungstate product is easy to achieve industrial mass production, and has a very high industrial application prospect.

• < Prev
• Next >