Ammonium Metatungstate Preparation

Ammonium metatungstate is an important tungsten compound, mainly used for petroleum cracking, organic synthesis, nitration reaction as a catalyst. With the rapid development of petroleum refining, petrochemical and other industries, the consumption of ammonium metatungstate increased rapidly. Relative to ammonium paratungstate, ammonium metatungstate prices are relatively high.

In the prior art, ammonium paratungstate is prepared by the crystallization method using ammonium paratungstate as a raw material, but there is a lot of investment, high cost and high energy consumption, and the quality of the obtained product is unstable, especially the solubility is poor, especially the low content of partial ammonium tungstate products, while the lower solubility of ammonium metatungstate products can not meet the needs of the production of tungsten-containing catalysts.

In order to improve the solubility of ammonium metatungstate, our scholars have explored a set of methods to prepare ammonium metatungstate at a lower cost. With ammonium paratungstate as raw material, the ammonium metatungstate product was obtained through leaching step and concentration step. The operation method is as follows:

1.Wet ammonium paratungstate was slowly added to the pure water with stirring while slowly adding 1: 1 to 1: 4 nitric acid (HNO₃) solution, the control solution pH 3 to 5, when the solution WO₃ content reaches 130 ~ 160g / l , boiled for more than 20 minutes, filtered to give dilute ammonium metatungstate solution;

2.Dilute ammonium metatungstate solution was allowed to stand aging 2 to 6 hours, filtered through a filter to obtain a filtrate 1; the filtrate was pumped into the reactor a plurality of heated concentrated, each time the filtrate into the filtrate 1 to 1: 4 ~ 1: 6 ammonia (NH₃ • H₂O) to adjust the solution pH 3 to 4; When the specific gravity of the solution reaches 1.8 to 2.2, stop pumping into the filtrate 1, cooling 1 to 4 hours, two-stage filtration to obtain filtrate 2; The filtrate 2 was pumped into the clarification tank, allowed to stand for 5 to 12 hours and then discharged through a suction filter for tertiary filtration to prepare a concentrated ammonium metatungstate solution.

3.The ammonium tungstate solution prepared by spray atomization drying equipment is used to prepare ammonium tungstate powder.

Using the above method, the wet ammonium paratungstate leaching step, wet ammonium paratungstate directly with nitric acid was prepared by the reaction of dilute ammonium metatungstate solution, compared with the prior art, omitted roasting process, without rotary furnace equipment, ammonium metatungstate product made of good fluidity, good solubility, high purity.

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