Ammonium metatungstate

The neutralization method uses ammonium paratungstate and nitric acid as raw materials to prepare ammonium metatungstate: Add ammonium paratungstate to deionized water and ammonium citrate to prepare a slurry containing WO312%-30%. According to ammonium paratungstate: nitric acid=1:20, add 3%～5% dilute nitric acid to the ammonium paratungstate slurry, control the solid-liquid ratio 1:(3～4), Ph value 2～4, heat to dissolve, make the relative density of the solution reach 1.18 ～1.20, heated to 80～90℃, controlled the Ph value at constant temperature and constant volume, stirred for 4h, aging for several hours, the clear liquid was concentrated to about 50% WO3 content, filtered to remove insoluble matter, the clear liquid continued to concentrate, cool to crystallize, It is made by drying to 80℃. Tungstic acid method dissolves tungstic acid in ammonia water, adds it to boiled deionized water, heats the ammonia with stirring to make Ph=8, adds acetic acid when the solution is boiling, and then adjusts the Ph value to 2～4 with dilute nitric acid. Continue heating and concentration to a relative density of 1.5-2, stop heating, cool and filter. The filtrate is fully stirred with ethanol, filtered after settling, and the crystals are dried at 80°C and crushed to obtain the product. Thermal decomposition method uses ammonium paratungstate as a raw material to prepare ammonium metatungstate: After fully mixing ammonium paratungstate and a small amount of citric acid catalyst, put them in a far-infrared rotary kiln, control the thermal decomposition temperature at 200-280℃, and decompose for about 1 h. At this time, some ammonia and water are removed, and the weight loss rate of ammonium paratungstate is 5% to 6%. The product after thermal decomposition immediately becomes slurry, add appropriate amount of ammonia water, adjust the Ph value in the range of 3-4, and digest the slurry at 90°C. It can be sold as a liquid product when the content of ammonium metatungstate is 50% by evaporation. When it is concentrated by evaporation to 20% of the original volume, the product is crystallized, separated by filtration and granulated. The evaporated concentrate can also be spray-dried to make the product. For example, if 45%-50% ammonium metatungstate is passed through a high-speed centrifugal rotary spray dryer, the temperature of the hot air at the inlet is 250-300℃, and the temperature at the outlet of the tower is 90-95℃, the resulting product is spherical crystals with a particle size of 200 meshes occupying 95 %, containing free water <1.5%. Solvent extraction method uses organic extractant di(2-ethylhexyl) phosphate (D2EHPA) or tributyl phosphate (TBP) to form an organic phase with kerosene solvent to extract ammonium ions in ammonium tungstate. The Ph value drops to 2 to 4, and ammonium metatungstate solution is generated after digestion. The product is obtained by concentrating crystallization, filtering and drying. The ion exchange method uses ammonium paratungstate as raw material to prepare ammonium metatungstate by ion exchange method: heat ammonium paratungstate at 130～140℃ for 1～8 h, adjust the product into slurry, boil it at 80～100℃ for 2～6 h, A solution of ammonium metatungstate is produced. After concentrating and crystallizing, filtering and drying, the product is obtained. The electrodialysis method uses ammonium tungstate or ammonium paratungstate as raw materials to prepare ammonium metatungstate through electrodialysis: ammonium paratungstate is added to the anode chamber, and when current passes, ammonium ions enter the cathode chamber through the anion exchange membrane, and the anode chamber ammonium metatungstate The concentration increases. Finally, the ammonium metatungstate solution is discharged from the cathode chamber and processed according to the above method to obtain ammonium metatungstate. Neutralization method, tungstic acid method and thermal decomposition method are the main methods of industrial production in my country.

It is used to produce tungsten catalyst, which is widely used in petroleum hydrocracking, lubricating oil hydrogenation, desulfurization, denitrification; also used for surface coating of various metal products, cemented carbide, etc.