Ammonium Dithiotungstate Preparation Process

Ammonium dithiotungstate (NH₄) ₂WO₂S₂ is an important thiometallic ammonium salt. After thermal decomposition, transition metal chalcogenide tungsten disulfide WS₂ can be obtained. It can be used in the synthesis of tungsten iron sulfur cluster compounds, semiconductors, superconductors, photoelectrochemical solar cells, hydrogen storage materials and electrode materials. It has good application and is the precursor of coal liquefaction and heavy oil hydrogenation catalysts. It can also be used as raw materials for the preparation of supported and non-supported tungsten sulfide hydrogenation catalysts. Therefore, it is of great significance to develop a high yield method for the preparation of high purity ammonium dithiotungstate.

The design principle of ammonium dithiotungstate is that the reaction of tungstate or tungsten trioxide with ammonium sulfide solution, the ammonia produced in the reaction process is discharged from the reaction solution by vacuum or inert gas is injected into the reaction solution, which promotes the reaction equilibrium to move towards the product ammonium dithiotungstate and to react. Ammonium dithiotungstate with high purity was prepared by adding appropriate ammonium salt to the solution to promote the precipitation of ammonium dithiotungstate. The process is as follows:

3.7g ammonium sulfide solution with 8% sulfur content was added to a single round bottom flask with magnets, and then 1g ammonium metatungstate was added to the flask. During the reaction process, the vacuum was pumped. After 5 hours of stirring reaction at room temperature, 0.1g ammonium chloride was added to crystallize for 0.5H. Then the solution was filtered by a Brinell funnel and distilled by cold distillation. After three times washing crystals with water (3 x 10 mL) and ethanol (3 x 10 mL) and drying at room temperature for 2 hours, 1.2 g yellow acicular crystals can be obtained in 99% yield (calculated as ammonium metatungstate).

By directly reacting tungstate or tungsten trioxide with ammonium sulfide solution, the ammonia produced in the reaction process is discharged from the reaction solution by vacuuming the reaction solution or by pouring inert gas into the reaction solution, which promotes the reaction equilibrium to move towards the product ammonium dithiotungstate, and adds appropriate ammonium salt to the reaction solution. To promote the production of ammonium thiotungstate two, high purity of two ammonium thiotungstate was prepared. The process has the advantages of less waste discharge, no need to use stimulating ammonia water and highly toxic and odorous hydrogen sulfide gas, simple process conditions, friendly environment and high yield of 98%. It is easy to realize large-scale industrial production and has a very high industrial application prospect.

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