Study of the structure, acidic, and catalytic properties of binary mixed-oxide MoO3-ZrO2 systems

Binary mixed-oxide materials based on MoO3-ZrO2 (1-68 Wt/Wt MoO3 nominal content) were prepared by a sol-gel method. The samples were characterized after calcination at 873 K by X-ray diffraction, Raman, UV-vis, and infrared spectroscopy. An increase in the molybdenum content produces an increase in the surface area up to ca. 140 m(2) g(-1) for a nominal MoO3 content of ca. 20 wt/wt. Simultaneously, the progressive generation of Bronsted acid sites attributed to the presence of surface polymolybdate species takes place. The Zr(MoO4)(2) crystalline phase coexists with polymolybdate species for catalysts with a nominal MoO3 content higher than 20 wt/wt. These samples show a lower surface area, but the number of Bronsted acid sites per unit of surface area remains almost constant up to ca. 30 Wt/Wt MoO3 content. A relationship between the structure of molybdenum surface species, the surface acidity determined by the adsorption of 2,6-dimethylpyridine, and the catalytic behavior of materials in the 2-propanol dehydration are reported.