Optimization of Phosphomolybdic Acid Synthesis using 31p NMR Data

A 31P NMR study was carried out to determine the composition of phosphomolybdic acids (PMA) formed in the reaction of molybdenum oxide and phosphoric acid with Mo/P molar ratio = 12. The molybdenum oxide conversion increases with dilution of the reaction mixture. The major product of this reaction over the entire range of conditions studied was the acid H7PMo11O39. The maximum concentration of H3PMo12O40 acid is achieved when the H2O:MoO3 mass ratio is 10, which is optimal for the preparative synthesis of PMA (84% yield).