Preparation of Ammonium Metatungstate by Solid Phase Method

Ammonium metatungstate is an important tungsten intermediate compound, which has the advantages of high activity, good solubility, convenient source and low price. It is mainly used in the manufacture of petrochemical industry catalyst tungsten carbide and other tungsten compounds, which are important for the production of tungsten carbide catalyst precursor.

thermal decomposition of ammonium metatungstate image

Tungsten carbide is widely used in the catalytic reaction of alkene dehydrogenation to olefin, olefin isomerization, hydrogenation reaction, because of its catalytic activity similar to metal platinum.

The advantage of solid-phase method is that the product has high purity, good solubility and short production process, but the corresponding accuracy is very high, the temperature control is not good, and it is easy to appear overburning or under burning. As a result, the quality is affected, so a good calciner must be prepared by the solid phase method, and the initial equipment is greatly invested.

The process of solid phase method:

1.Pyrolysis steps: Zero ammonium paratungstate (APT) as raw materials, adding three rotary furnace from the feeding port quantitatively, at a temperature of 240-290℃ in 2-3 times each baking, roasting time 45-75min, the total heat loss rate control roasting in 6-8%, get secondary the thermal cracking product of ammonium tungstate;

2.Pulp conversion steps: Ammonium paratungstate pyrolysis products was dissolved in deionized water, the transformation in 90 - 95℃, pH 3-4 under the condition of transformation after aging, cooling, clarification, filtration, removal of insoluble materials, prepared into clear liquid;

3.Evaporation steps: step B transformation filtering liquid prepared by evaporation, keeping the solution pH from 3 to 4, when the solution density is stop at 1.8-2.0g/cm3, aging, cooling, clarification, filtration, removal of insoluble, prepared concentrated solution;

4.Spray drying steps: the condensed liquid is transferred into the spray drying equipment to dry, and the hollow spherical ammonium tungstate product is prepared.

As a result of thermal cracking of APT in the three stage rotary furnace equipment, and strictly controlling the operation parameters such as calcination temperature, roasting time and baking times, the purity and weightlessness rate of pyrolysis products were detected. In order to effectively improve the conversion rate of pyrolysis and pyrolysis product purity, solves the cracking in the process of roasting "owing to burn" and "burn", conversion rate and other issues, so as to realize the production of ammonium metatungstate pyrolysis industrialization, conversion rate of more than 97%, improve the product purity.

 

 

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