Ammonium Metatungstate Classes and Usage

Ammonium metatungstate can be used as reagents for chemical analysis such as for chemical diagnosis; source material for the preparation of high purity tungsten trioxide used as a thin film substrate for certain semiconductor devices; high purity source material for research in tungsten chemistry; source material for DENOX catalysts industry; as a precursor to a variety of POM (polyoxometalates). Ammonium metatungstate applied in the manufacture of various petrochemical catalysts, It's the basic raw material of W-base catalyzer used in oil refinery.  

It has different classes listed as below:

Class	AMT-1	AMT-2
WO3(%)	≥88	≥84
Water Solubility	300g/100ml
Fe	0.002	0.005
Si	0.002	0.006
Mo	0.01	0.03
Cu	0.001	0.001
M	0.001	0.001
Mg	0.001	0.001
Sn	0.0001	0.002

ammonium metatungstate

Ammonium metatungstate is a source of high purity, water soluble tungsten which is essentially free of alkali and other metallic impurities. Ammonium metatungstate is very versatile and can be used as catalysts, capacitors, nuclear shielding, flame retardants, corrosion inhibitors raw materials, but also excellent raw materials in the preparation of ultra fine tungsten powder, tungsten heavy alloy powder, phosphotungstic acid, arsenic acid, silicon tungstate.

It is also used as a raw material for the production of tungsten catalysts for a variety of reactions including oxidation, hydroxylation, hydrogenation, and polymerization. Suitable carriers can be impregnated with alkali-free solutions of tungsten and processed to remove the water and ammonia. Such catalysts are used by the petrochemical industry.

Other applications include: reagents for chemical analysis such as for chemical diagnosis; source material for the preparation of high purity tungsten trioxide used as a thin film substrate for certain semiconductor devices; high purity source material for research in tungsten chemistry; source material for DENOX catalysts industry; as a precursor to a variety of POM (polyoxometalates).

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Ammonium Metatungstate Introduction and Its Advantages

Ammonium metatungstate, also known as AMT, is a tungsten chemical in the form of highly soluble hydrated crystals, solubility is 303.99/loogH:O when 20℃, aqueous fairly stable. It is white or slightly yellow crystals which has no harmful components and slightly acidic.

Component of ammonium metatungstate is listed as below:

ammonium metatungstate

Grade		AMT-1A	AMT-2A
		AMT-1B	AMT-2B
		AMT-1C	AMT-2C
Purity Min.(%)		99.95	99.9
Main content WO3 MIN.(%)		83	83
Other Chemical Element Content Max.(%)	Al	0.001	0.001
	As	0.001	0.001
	Bi	0.0001	0.0001
	Ca	0.001	0.003
	Cr	0.001	0.001
	Cu	0.001	0.003
	Fe	0.002	0.003
	K	0.0015	0.002
	Mg	0.001	0.002
	Mn	0.001	0.001
	Mo	0.005	0.01
	Na	0.0015	0.002
	Ni	0.001	0.001
	P	0.001	0.003
	Pb	0.0001	0.0001
	S	0.0005	0.001
	Sb	0.001	0.002
	Si	0.001	0.002
	Sn	0.0001	0.0003
	Ti	0.001	0.002
	V	0.001	0.002
Insoluble Matter in Water		0.5	0.5
PH Value		3.0-4.5	3.0-4.5

Ammonium metatungstate is being used more frequently with the development of tungsten industry.
Its great solubility can be matched into 1.3-2.1 aqueous solution which can meet the demand of tungsten containing catalyst. Normally in order to reduce diffusion resistance, tungsten concentrate in solution should be lower. When producing doped tungsten powder, tungsten concentrate should be higher which can be achieved through adjust, so that it can reduce heat exhaustion. During the producing process, ammonium metatungstate can be pyrolysised to obtain highly active pyrolysate. Doped tungsten trioxide made from this process can be used to conduct hydrogen reduction. 

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Ammonium Metatungstate Prepares WO3 Contained Hydrodesulfurization Catalyst

Boehmite is the main raw material to produce aluminum oxide. γ-Al₂O₃ obtained by the calcination of boehmite as the carrier, and load nickel oxide and tungsten trioxide, add a additive-fluorine, thus to produce tungsten trioxide hydrodesulfurization catalyst with high activity. The different purities of boehmite have a certain degree of influence on the activity of the desulfurization catalyst.

Boehmite 

Low-purity boehmite prepares WO₃ hydrodesulfurization catalyst

1. Take aluminum hydroxide powder generated by aluminum sulfate- sodium aluminate method from boehmite with a purity of 35% by weight, add the extrusion aid and water, extruded strip of 1.2 mm in diameter, dry in an oven at 120 ℃for 4 hours and then roasted at 550 ℃ in a tube furnace under the air for 4 hours to obtain γ-Al₂O₃ (A);

2. Dissolve ammonium fluoride in deionized water, add the carrier which is cooled down to room temperature for impregnation for 4 hours at room temperature;

3. Separate and dry the wet fluorinated alumina bar in an oven at 120 ℃ for 4 hours, then heated at 500 ℃ in a tube furnace with dry air for 4 hours to obtain fluorinated alumina strip, removed and cooled down to room temperature;

4. Add fluorided alumina to the deionized water containing with ammonium metatungstate and nickel nitrate, and separate after dip at room temperature for 4 hours to obtain wet catalyst;

5. Dry the wet catalyst in an oven at 120 ℃ for 4 hours, and calcine under the air in a tube furnace at 500 ℃ for 4 hours to obtain the catalyst A.

High-purity boehmite prepares WO₃ hydrodesulfurization catalyst:

1. Take aluminum hydroxide powder (obtained from the hydrolysis of aluminum alkoxide) with the boehmite purity of 70% by weight, add extrusion aid and water, then squeeze to a strip with a diameter of 1.2 mm, dry in an oven at 120 ℃ for 4 hours, then calcine at 550 ℃ for 4 hours in a tube furnace accompanying with the air to give γ-Al₂O₃ (B);

2. γ-Al₂O₃ (B) for the preparation of the carrier catalyst B, the same preparing method of the low purity boehmite.

Analysis showed that the aluminum oxide generated from high-purity of boehmite has the larger amount of acid, while the boehmite prepared by calcination has a larger amount of strong acid; tungsten desulfurization catalyst B prepared by aluminum alkoxide hydrolysis of a high-purity oxide boehmite has a higher activity.

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Ammonium Metatungstate Prepares Tungsten Copper EFP Liner

 Tungsten Copper

By comparison, tungsten copper W-Cu system combines high hardness, high density, high strength and excellent chemical properties of W and excellent thermal conductivity of and plasticity of Cu. Since there is a big difference between W and Cu (W-3410℃，Cu-1083℃), After the explosion of copper is evaporated leaving a high hardness, high density hard phase tungsten, compared to copper Liner armor penetration depth can be increased by nearly 30%. Therefore, tungsten copper EFP liner has a broad application prospect in the future. Ordinary tungsten powder, copper powder and ultra-fine tungsten-copper composite powder prepared tungsten copper EFP Liner and its performance was compared. Wherein ultrafine tungsten copper composite powder is prepared by using spray pyrolysis, it uses a proportion of copper nitrate andammonium metatungstate dissolved in distilled water into the mixed solution, and then the pressure centrifugal spray drier precursor powders, the precursor powder is then placed in roasting reduction furnace. Finally, wet ground and placed in a ball mill reduction in the reduction furnace, ultra-fine tungsten-copper composite powder particle size is formed between 100-300nm.

After the tungsten copper rod made of tungsten copper EFP started liner blank forging, which blank deformation has three steps: 1. upsetting the blank in the mold, in this process the blank upper and lower parts deformation occurs first, and upper and lower portions of the pores gradually become less under the influence of compressive stress, density increases, increasing the contact area with the punch, friction force increases, under the action of the metal tensile stress generated lateral flow; 2. metal flows hindered by the mold wall and it will flow along with the hole of the mold bottom, and in the process the pores reduces and the density increases; finally, when the metal flow to the ejector rod will enter the multi-pressure stage, mainly through its hydrostatic pressure to eliminate rough pores, so the effect is not significant.

In addition, in the process of tungsten copper EFP liner blank forging, there are two ways of deformation of the matrix material, one is only copper phase deformation, deformation does not occur with tungsten and tungsten particles along the direction of deformed copper matrix flow was streamlined distribution; the other one is both of Cu and W phase have deformation and form fibrous structure. In order to ensure that the final density, tensile strength and elongation to achieve the desired requirements, we should make a reasonable design for tungsten copper EFP liner shape and have sufficient deformation.

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Ammonium Metatungstate Prepares Tephra Contained Tungsten Trioxide Denitration Catalyst

Tephra is defined as the gravel and mineral particles which are erupted from a volcano and the granule less than 2 mm in diameter. At the explosive of the volcanic activity, the solid rocks and lava are broken down into the fine particles and formed to volcanic ash. In the mix materials of some pozzolana, there are active ingredients, such as a certain number of active silica, activated titanium oxide.

The coal takes the domination of China's energy structure, and one of the main sources of air pollution is the nitrogen oxide which is produced by the consumption of coal; the nitrogen oxide will not only cause acid rain, photochemical smog and other issues which damages to the global environment, but also seriously endanger human health. Conventional manufacturing of honeycomb catalyst is taking tungsten trioxide and nanoscale titanium dioxide as the main raw material, and mixing with water, binders, extrusion aid, reaming, lubricants, glass fibers and so on to fully kneaded to obtain a plastic pug, then extruded to wet honeycomb catalyst, finally get the molded catalyst after drying and calcining.

tephra and denitration catalyst

Study has found that the tungsten trioxide denitration catalyst containing tephra which the components include: nano titanium dioxide powder 72~81, volcanic tephra 5~15, ammonium metatungstate 0.9~3, ammonium metavanadate 0.7~2, monoethanolamine 2~6, carboxymethyl cellulose 2, Polyoxyethylene of 2, 1~3 lanthanum nitrate (Remarks: the unit is part). The preparation method is as follows:

1. Mix the monoethanolamine, deionized water and ammonium metavanadate together, and fully dissolved by heating and stirring to prepare a solution of ammonium metavanadate;

2. Respectively dissolve lanthanum nitrate and ammonium metatungstate in water at room temperature, continually stirring for 1 hour to obtain the solution of ammonium metatungstate and lanthanum nitrate;

3. Mix the tephra, nano titanium dioxide with deionized water, ammonium metavanadate and ammonium metatungstate solution, polyethylene oxide, lanthanum nitrate solution for high-speed mixing evenly, then standing for 1-12 hours to obtain pug;

4. Warmed and dried the pug;

5. Calcine the dried pug, which is obtain the tungsten trioxide denitration catalyst products containing tephra after calcined at a maximum temperature of 600°C for 30 hours.

Studies have shown that it can reduce the high amount of conventional titanium dioxide by adding volcanic tephra, thereby reducing costs; tungsten trioxide decomposed from the calcination of ammoniummetatungstate in the production process; the cost will be reduced, compared with directly using nanoscale titanium dioxide which containing tungsten trioxide as a raw material; the added polyethylene oxide in calcined product improving pore volume and distribution of the products, increasing the specific surface area, thus to effectively improve the denitration performance; therefore, we will know this kind of tungsten trioxide denitration catalyst containing tephra has a low manufacturing cost, high specific surface area of catalyst products, wide operating temperature, and has the advantage of good catalytic denitration performance at the same time.

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Ammonium Metatungstate Prepares Tungsten Oxide Nanotube

When particle size of some material reaches to nano grade (1~100nm), it can show many special reactions. It can be widely applied in functional information display, catalyst, magnetic material. Among which, tungsten oxide has various crystalline structure, it has a large amount of non-stoichiometry oxide form and has multi-functional broad-band gap semiconductor material. WO₃ is widely applied in gas sensor, photocatalyst, gasochromism, electrochromism, photochromism and solar cell due to its unique electricity, optical configuation, and magnetic property. Apart from that, temperature induces structure phase transition which results in the changes of volume, resistance and color greatly draw people’s attention. The research on its special structure has become the focus of recent study.

WO3-nanotube-SEM

The traditional preparing method of tungsten oxide nanotube need extra coating and sculpture process, the quality of nanotube greatly depends on the control of processing steps. By coaxial electrospinning, hollow nano fiber can be obtained, manufacturing process is simplified.

Raw material: PVA; ammonium metatungstate; absolute ethyl alcohol; aluminum foil; deionized water.

Preparing process:
(1) Weigh a certain amount of PVA to dissolve in deionized water, stirring it for 4hous in constant temperature of 80℃ and prepare it to 15% PVA solution. Then add 24ml alcohol and 6g ammonium metatungstate solution into 60ml PVA solution.
(2) Dilute another 15% PVA solution to 10% as inner pipe solution by deionized water. Inject both inner and outer pipe solution into injector, then inject them into electrostatic spinning coaxial needle.
(3) Under electric voltage 9~15kV, keep spinning with receiving distance of aluminum foil for 10~12cm. Dry the obtained composite fiber in thermotank for 12 hours, keep the temperature to 600℃ by putting it in muffle furnace, and then cool it down to get WO₃ nanotube.

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