Ammonium Metatungstate Preparing Ammonium Tetrathiotungstate

ammonium tetrathiotungstate image

Ammonium tetrathiotungstate [(NH4)2WS4], which is short for ATTT, is widely applied in the synthesis of biological nitrogenase activity center - tungsten iron sulfur atom cluster compounds, also is the precursor of coal liquefaction and heavy oil hydrogenation catalyst, and also can be raw material for preparing supported tungsten sulfide hydrogenation catalyst. The traditional way to produce ammonium tetrathiotungstate from the raw material of ammonium metatungstate (AMT) is introducing hydrogen sulfide gas into ammonia solution with AMT, wherein the hydrogen sulfide gas is generated by sodium sulphide (Na2S) and phosphoric acid in situ method. However, since this method will take a long reaction time, consume a large number of sodium sulphide and phosphoric acid, and also will discharge much rubbish, moreover, it also involves the treatment of toxic and stinking hydrogen sulfide gas, and thus has been eliminated.

For shortening the reaction time, reducing pollution to the environment, and obtaining high purity product at the same time, an invention has pointed a method to prepare ammonium tetrathiotungstate from raw materials of ammonium metatungstate (AMT), concentrated ammonia water and ammonium sulfide solution, the steps are shown as following:
1. Weight a certain amount of ammonium metatungstate powder and add distilled water, control the ratio of dosage distilled water and AMT at among 3 ~ 6/1 (Calculated by ml/g);
2. Add a certain amount of concentrated ammonia water with stirring and heating to 40～60℃ to dissolve, the ratio of dosage concentrated ammonia water and AMT is 1～2/1 calculated by ml/g;
3. Control the solution temperature among the room temperature (25℃) to 90℃, then add ammonium sulfide solution with sulfur content of 6～12％ with stirring, the mole ratio of sulfur and tungsten in the added amount of ammonium sulfide solution and reactant liquid is 4~6 to 1, and stir for 0.5~3 hours to get blood red liquid;
4. After the reaction finished, take out the reactant to cool to room temperature and get it crystallize for 8~24 hours, then filter the solution with crystal and wash them with cold distilled water for 3 times, finally wash the crystal with anhydrous ethanol for 2~3 times, then carry out drying solvent, drying under room temperature for 24 hours to get dark red needle crystal of ammonium tetrathiotungstate.

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