Effect of high temperature treatment on the properties of fe-mo oxide catalysts

In this study the structural and compositional changes that Fe-Mo oxide catalysts undergo during treatment at elevated temperatures were investigated. Commercial and laboratory prepared catalysts were examined. The changes in catalyst properties were determined by low temperature nitrogen adsorption, scanning electron microscopy, X-ray diffraction, X-ray fluorescence and thermogravimetric analysis. The activities of the catalysts for the oxidation of methanol in air to formaldehyde were measured using an integral bed reactor. The results showed that treatment at elevated temperatures resulted in the growth and segregation of Fe₂(Mo0₄)₃ and Mo0₃ crystals resulting in a loss of specific surface area. The changes in specific activity can be explained in terms of molybdenum depletion from a molybdenum rich iron molybdate phase.