Ammonium metatungstate (AMT), as an important inorganic compound, possesses unique physicochemical properties and is widely used in ceramics, textiles, and catalysts. AMT has the following characteristics:
AMT typically appears as a white crystalline powder or a slightly yellowish solid, which gives it an advantage in applications requiring specific colors, such as providing a relatively pure hue when used as a ceramic colorant.
AMT is highly soluble in water, with a solubility of up to 300 g/100 mL at 25°C. This high water solubility stems from its Keggin-type polyoxoanion structure ([H?W??O??]??), which has a surface rich in polar oxygen atoms capable of forming strong hydrogen bonds with water molecules, enhanced by the presence of crystal water that increases hydrophilicity. AMT is also soluble in ammonia water. In low-concentration ammonia water, its solubility is approximately 300-320 g/100 mL (at 25°C); in high-concentration ammonia water, solubility may slightly decrease to 280-300 g/100 mL due to the partial conversion of polytungstate ions into other tungstate species. However, AMT is sparingly soluble in common organic solvents such as ethanol, acetone, and benzene.
AMT exhibits excellent catalytic properties. It can serve as a catalyst or catalyst precursor in various organic and inorganic reactions. For instance, in petrochemical processes like hydrodesulfurization and hydrocracking, catalysts derived from AMT after appropriate treatment can effectively enhance reaction rates and selectivity, lowering the activation energy and enabling reactions under relatively mild conditions.
AMT has high purity, with common grades such as AMT-1A and AMT-2A reaching purities of 99.95% and 99.90%, respectively. Additionally, it has stringent requirements for the content of other chemical elements, with low levels of impurities like Al, As, and Bi, which is critical for its use in high-precision applications.
