Ammonium Metatungstate by Spray Drying Preparation

Promoted by the vigorous development of petroleum processing industry, especially in the petroleum cracking and organic synthesis industries, the research and development of tungsten catalysts have received widespread attention. Ammonium metatungstate, as the most important precursor of tungsten-containing catalysts and tungsten metal, has the advantages of high water solubility and non-toxicity, so it is widely used as a tungsten source.

Recently, the method of preparing ammonium tungstate powder by spray drying method has been popularized. Some scholars first used spray drying method to treat the morphology of ammonium tungstate. Then, adding inorganic ammonium carbonate, which was easy to decompose volatilization in spray drying process, to decompose the spherical structure obtained by spray drying to obtain highly dispersed ammonium tungstate particles, and achieved different results. The contents are as follows:

First, ammonium carbonate and ammonium metatungstate were mixed at a mass ratio of 3:10, and then prepared into a total mass fraction of 20% ammonium carbonate-ammonium tungstate aqueous solution, ultrasonically shaken for 10 minutes, and then introduced into a spray dryer to control hot air. The inlet temperature of the nozzle was 200 °C, the flow rate of the control gas was 350 ml/min, and the feed rate was 30 ml/min. After spray drying, a dry high dispersion sheet of ammonium metatungstate was obtained. The SEM image shows that ammonium metatungstate has a sheet-like structure with a thickness of about 100-250 nm. The particle size distribution was around 3 um, and the bulk density was reduced to 0.104 g/ml.

A high dispersion of ammonium tungstate was obtained by adding ammonium carbonate inorganic salt into the precursor solution and spray drying. The preparation method is simple, and the flake nanometer ammonium metatungstate particles can be obtained directly without evaporating liquid or physical separation treatment. Moreover, no organic solvents or catalysts are used in the whole process, which makes the preparation process pollution-free and environmental protection cost effectively reduced.

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