Precise control and continuous production of β-ammonium tetramolybdate in concentric reactor

β-ammonium tetramolybdate [β-(NH4)2Mo4O13] was prepared in a concentric structure reactor.The species and microstructure of Mo with the change of solution acidity in the preparation process were investigated. The results showed that the pH of the solution should be controlled below 2.5 to obtain ammonium tetramolybdate crystals. In the acidification process, NH3·H2O was used to adjust the pH back to about 3.0 to dissolve the fine crystals produced and facilitate the conversion of ammonium heptadmolybdate to ammonium tetramolybdate. Decreasing the soaking time between the (NH4)4Mo4O12(O2)2·2H2O crystals and the original liquor was beneficial to obtaining β-(NH4)2Mo4O13.Based on the polymerization mechanism of molybdenum, a multi-lattice concentric circle reactor was designed to realize the regional regulation of ammonium molybdate crystallization. High-quality β-(NH4)2Mo4O13 was prepared continually by periodically adding HNO3 solution, ammonia water, and product slurry under specified conditions.