Freeze-dried precursor-based synthesis of nanostructured cobalt-nickel molybdates Co1-xNixMoO4

A simple processing route to nanostructured mixed cobalt-nickel molybdates, Co 1-x Ni x MoO 4 (0 ≤ x ≤ 1), has been developed. It is based on the use of precursors resulting from the freeze-drying of aqueous solutions of the appropriate common metal salts. Thermal decomposition of amorphous freeze-dried powders at low temperatures produces the nanostructured mixed oxides. A study of the influence of the preparative variables on the outcomes of this procedure is presented. The resulting materials have been characterized by X-ray powder diffraction, elemental analysis, scanning electron microscopy, thermogravimetry under oxygen flow, and physisorption measurements. Co 1-x Ni x MoO 4 grains (obtained by calcination below 773 K) are aggregates of nanometric particles (with diameters typically around 30-40 nm) and have relatively high specific surface areas (20-40 m 2 /g). The catalytic activity of the nanostructured cobalt and nickel molybdates for the oxidative dehydrogenation of propane has been evaluated. The performance of these nanostructured catalysts in this process is higher than those reported for homologous oxides prepared through conventional procedures.