Ammonium metatungstate microsphere may be prepared by two different spray drying methods.
Ammonium metatungstate (AMT) is usually used as one of the precursors of tungsten carbide (WC) catalysts. And the morphology and particle size distribution of WC microsphere are affected by the properties of precursor. In other words, AMT properties will have an important influence on morphology and particle size distribution of WC microsphere and have a finally effect on the catalytic activity of WC catalyst. Therefore, it is necessary to study AMT to prepare WC catalysts with excellent catalytic performance.
Ammonium Metatungstate Microsphere Prepared by Spray Drying Method
The morphology of AMT microsphere prepared by airflow spray drying method and morphology of AMT microsphere prepared by centrifugal spray drying method are different. The morphology and particle size of the two types of microspheres were studied. The results show that:
1. The morphology of the powder prepared by centrifugal spray drying is solid sphere, and it is different from that of the powder prepared by airflow spray drying, which is hollow sphere.
2. For the airflow spray drying method used, the effects of solution concentration, feed rate and surfactant on the particle size of products were investigated. It was found that the solution concentration is the most important factor affecting the particle size.
3. Under different drying conditions, the minimum median diameter (d50) of the dry products is 2.26μm.
This method might provide a referential foundation for the morphology and particle size control of hollow global WC microspheres prepared by the gas-solid reaction method of spray drying sphere miniaturization.
In the airflow sprayer dryer preparing AMT microsphere picture:
1. air inlet; 2. electric heater; 3. concentric inlet of the hot air around the spray nozzle; 4. spray cylinder; 5. cyclone for separating particles from gas stream; 6. collecting vessel for dried product; 7. outlet filter; 8. aspirator for pumping air through system; 9. feed inlet.
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