ELECTRON-MICROSCOPY OF SOME MOLYBDENUM OXIDE PHASES AFTER USE AS CATALYSTS IN OXIDATIVE AMMONOLYSIS AND AMMOXIDATION OF TOLUENE

Five molybdenum oxide samples, subjected to conditions of oxidative ammonolysis and ammoxidation of toluene at 450 and 460 degree 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 MoO//3 crystals are reduced to smaller MoO//2 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 less than 0. 1 m**2/g to almost 40 m**2/g. In subsequent ammoxidation, MoO//2 transforms first into orthorhombic Mo//4O//1//1 and finally into MoO//3.