Electron microscopy of some molybdenum oxide phases after use as catalysts in oxidative ammonolysis and ammoxidation of toluene

Summary, in English

Five molybdenum oxide samples, subjected to conditions of oxidative ammonolysis and ammoxidation of toluene at 450 and 460°C, respectively, have been characterized using X-ray diffraction, scanning and transmission electron microscopy, and specific surface area measurements. In oxidative ammonolysis, the relatively large, freshly prepared MoO3 crystals are reduced to smaller MoO2 crystals with a crystallite size of 5–30 nm. This process gives a perfectly pseudomorphous product with pores less than 5 nm. The specific surface area increases from <0.1 m2/g to almost 40 m2/g. In subsequent ammoxidation, MoO2 transforms first into orthorhombic Mo4O11 and finally into MoO3. The crystals of Mo4O11 are about 1 μm in diameter, and their formation leads to a decrease of specific surface area. The original MoO3 morphology is retained even after the sequence of transformation as follows: MoO3 → MoO2 → Mo4O11 (→MoO3). In some cases, the new generation of MoO3 crystals grows parallel to the original MoO3 crystals.

• Author: Staffan Hansen; Arne Andersson
• Department/s: Department of Chemistry; Division of Chemical Engineering
• Publishing year: 1988
• Language: English
• Pages: 225-243
• Publication/Series: Journal of Solid State Chemistry
• Volume: 75
• Issue: 2
• Links: http://dx.doi.org/10.1016/0022-4596(88)90162-4
• Document type: Journal article
• Publisher: Elsevier
• Topic: Chemical Engineering
• Status: Published
• ISBN/ISSN/Other: ISSN: 0022-4596