THE EFFECT OF THE PREPARATION METHOD ON THE NATURE AND DISPERSION OF SURFACE SPECIES FORMED UPON REACTION OF MOLYBDENUM TRIOXIDE WITH ALUMINA AND TITANIA

Titania- and alumina-supported molybdenum-containing systems have been prepared from mechanical mixtures of the support and molybdenum triox ide. The systems have been characterized by X-ray diffraction, tempera ture-programmed reduction and scanning electron microscopy, and Fourie r transform-infrared monitoring of pyridine adsorption has been used t o determine surface acidity. Dispersion of the supported phase, and it s transformation to well-dispersed species has been attained by mechan ical grinding and calcination in air, or by hydrothermal treatment of such mixtures and calcination. In the latter case, a higher dispersion is reached, despite the shorter time of calcination. Also hydrotherma lly treated samples show a larger concentration of surface Bronsted ac id sites.