Ammonium metatungstate (AMT) is an appearance of white or slightly yellow crystalline powder, its water-soluble is 300g / 100ml, it slightly soluble in water; when the temperature reaches at 20 ℃, its solubility is less than 2%. Ammonium metatungstate is used in making metal tungsten, steel, fireproof fabric and for the ceramic industry. Usually, we take ammonium tungstate solution as raw material to obtain ammonium metatungstate solution by solvent extraction or ion exchange method, and then evaporate it to prepare crystals of ammonium metatungstate. Ammonium metatungstate is also used in the manufacture of various petrochemical catalysts and other tungsten compounds, and it is the main raw material refinery tungsten-based catalyst. According to the features of ammonium metatungstate slightly soluble in water, we prepare tungsten trioxide in this case.
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Ammonium metatungstate preparing tungsten trioxide is based on taking ammonium metatungstate as raw materials, heating ammonium metatungstate to 220-280 ℃; it can be converted to ammonium metatungstate when it loses some ammonia and crystal water, and then continue to heat ammonium metatungstate to more than 600 ℃, when ammonium metatungstate loses all crystal water and ammonia, cooling and crystallization, the finished product is dried thoroughly into yellow tungsten trioxide.
There many methods of preparation of ammonium metatungstate, such as acid method, thermal decomposition method, ion exchange, solvent extraction method. The method of ammonium metatungstate preparing tungsten trioxide is simple and easy, and it meets the needs of industrial production.
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