Ammonium phosphomolybdate preparation

Ammonium Dimolybdate, (NH4)2Mo.j07.H20, exists as mono-clinic (prismatic) crystals. A compound (NH4).2Mo20,.3NH2 has been prepared by addition of ammonium hydroxide of medium strength to solid ammonium phosphomolybdate. This substance loses ammonia, yielding the dimolybdate. 

Prepare ammonium phosphomolybdate and after washing with water, boU with nitric acid and expel NH evaporate to dryness and dissolve in 2 M nitric acid. 

Molybdate-Based Catalysts. The first catalyst commercialized by SOHIO for the propylene ammoxidation process was bismuth phosphomolybdate, Bi9PMoi2052, supported on silica (9). The catalytically active and selective component of the catalyst is bismuth molybdate. In commercial fluid-bed operation, the bismuth molybdate catalyst is supported on silica to provide hardness and attrition resistance in the fluidizing environment. Bismuth molybdate catalysts can be prepared by a coprecipitation procedure using aqueous solutions of bismuth nitrate and ammonium molybdate (10). The catal3ret is produced by drying the precipitate and heat treating the dried particles to crystallize the bismuth molybdate phase. Heat treatment temperature for bismuth molybdate catalysts is generally arovmd 500°C. 

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