The English abbreviation of ammonium metatungstate is AMT. This is a metallic tungsten chemical and is in the form of highly soluble hydrated crystals. Ammonium metatungstate is an important tungsten-containing compound, which is mainly used as a catalyst in petroleum cracking, organic synthesis, and nitration reactions. Ammonium metatungstate is mainly used in industry as a raw material for the production of tungsten catalysts, and is used in different chemical reaction systems, including oxidation, hydroxylation, hydrogenation and polymerization systems. With the rapid development of petroleum refining, petrochemical and other industries, the consumption of ammonium metatungstate has increased rapidly.
The method for preparing ammonium metatungstate by using ammonium paratungstate as raw material, using ammonium paratungstate as raw material, and obtaining ammonium metatungstate product through leaching steps and concentration steps, is characterized in that the leaching step is directly implemented on the ammonium metatungstate raw material; and after the concentration step , and obtain ammonium metatungstate product through the step of spray drying. The method further comprises three steps: wet ammonium paratungstate leaching, conversion of the dilute ammonium metatungstate solution into a concentrated metatungstate solution, and spray drying of the concentrated ammonium metatungstate solution. Compared with the prior art, the method of the invention omits the roasting process, does not need to use rotary kiln equipment, reduces fixed investment and reduces production cost. The ammonium metatungstate product prepared by the method has good fluidity, good solubility and high purity, which overcomes the disadvantage of low solubility of the ammonium metatungstate product in the prior art.
Using ammonium paratungstate as raw material, ammonium metatungstate is prepared through three steps of wet ammonium paratungstate leaching, dilute ammonium metatungstate solution is converted into concentrated metatungstate solution, and concentrated ammonium metatungstate solution is spray-dried as follows:
- Wet ammonium paratungstate leaching: wet ammonium paratungstate (water content 5-10%) is mixed with dilute nitric acid (HNO3) to prepare dilute ammonium metatungstate solution. The chemical reaction is as follows:
5(NH4)2O•12WO3•5H2O+4HNO3＝(NH4)6H2W12O40•6H2O+4NH4NO3
- Dilute ammonium metatungstate solution is converted into concentrated metatungstate solution: the dilute ammonium metatungstate solution prepared in step A is left to age for many times, filtered, heated and concentrated, and then filtered to prepare concentrated ammonium metatungstate solution.
- Spray drying of the concentrated ammonium metatungstate solution: the concentrated ammonium metatungstate solution prepared in step B is spray-dried, so that the feed liquid is quickly dried into powder.
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