Morphology and Size of Ammonium Metatungstate Microsphere Prepared by Spray Drying Method

Ammonium metatungstate (AMT) is usually used as one of the precursors of tungsten carbide (WC) catalyst, and the properties of AMT precursor affect the morphology and size distribution of WC microsphere, which have a finally effect on the catalyst activity.

In this work, the mechanisms of airflow and centrifugal spray drying methods were introduced, then the AMT microspheres having different morphologies were prepared by using these two kinds of spray drying methods, and the morphology and size of the microspheres prepared were studied. The results show that 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. 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, and under different drying conditions, the minimum median diameter (d50) of the dry products is 2.26 μm. This study might provide a referential foundation for the morphology and size control of hollow global WC microspheres prepared by the gas-solid reaction method of spray drying sphere miniaturization.