Ammonium Tetrathiotungstate

Ammonium Tetrathiotungstate (NH₄)₂WS₄ is a yellow-orange, water-soluble salt.  It is a precursor for Tungsten Disulfide, an important catalyst in the petrochemical industry.  Tungsten Disulfide is also a high-performance solid lubricant used for applications with high load and temperature requirements.

At moderate temperatures and in an inert atmosphere of helium gas, Ammonium Tetrathiotungstate will decompose to produce Tungsten Trisulfide. When elevated to higher temperatures it will lead to further decomposition and the formation of Tungsten Disulfide and Sulfur.  Tungsten Disulfide is used in hydrodesulfurization to remove Sulfur from crude oil.

Ammonium Tetrathiotungstate is an optimal precursor because the decomposition product has a high surface area.  The surface area and pore size distribution were found to be ideal for use as a catalyst.

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