Mechanochemical preparation of vanadium- and molybdenum-containing catalysts II: The effect of mechanochemical activation of vanadium pentoxide + ammonium dimolybdate compositions on chemical and phase transformations

Abstract

We studied the effect of mechanochemical treatment (MCT) of V2O5 + (NH4)2Mo2O7 compositions (V: Mo = 0.7: 0.3) in ethanol, water, and air on the physicochemical properties of the compositions. X-ray powder diffraction, differential thermal analysis (DTA), and IR spectroscopy showed that mechanochemical treatment in water or ethanol does not change the phase state of vanadium pentoxide. (NH4)2Mo2O7 partially decomposes during MCT to yield nonstoichiometric molybdenum oxides. MCT in water leads to the complete decomposition of (NH4)2Mo2O7, and the nonstoichiometric molybdenum oxides that have been formed in 60–120 min are segregated into a molybdenum phase during further treatment for 240–360 min. During such a treatment, V2O5 first forms V2O5 · nH2O intercalation compounds, which then react with ammonia during long-term treatment to form ammonium hexavanadate (AHV).