Surface and catalytic properties of MoO3-treated Co3O4/Al2O3 solids

The surface and catalytic properties of Co3O4/Al2O3 solids treated with dif ferent proportions of MoO3 were investigated, the extent of MoO3 added vary ing between 0.50 mol% and 5.00 mol% (0.63-5.9 wt%). The pure sample was pre pared by thermal decomposition at 600 degrees C of aluminium hydroxide impr egnated with a calculated amount of Co(NO3)(2) dissolved in the least amoun t of distilled water. The MoO3-treated samples were prepared by thermal dec omposition at 600 degrees C of aluminium hydroxide treated with different p roportions of ammonium molybdate followed by treatment with Co(NO3)(2) solu tion. The crystalline phases produced by thermal treatment of the pure and treate d samples precalcined at 600 degrees C were characterized using an XRD tech nique. The surface and catalytic properties of the various catalysts were s tudied using nitrogen adsorption at -196 degrees C and CO oxidation by O-2 at 100-150 degrees C. The results obtained revealed that molybdena treatment of the Co3O4/Al2O3 s olids followed by precalcination at 600 degrees C resulted in a decrease in the degree of crystallinity of the Co3O4 phase produced. This treatment ef fected a progressive small increase in the specific surface area of the tre ated solids (ca. 10%). However, the catalytic activity was found to be incr eased considerably by increasing the amount of MoO3 added (184%), reaching a maximum limit at 1.00 mol% MoO3. The activation energies of the catalytic reaction calculated for both the p ure and MoO3-treated solids suggested that MoO3 treatment did not modify th e energetic nature of the active sites (surface cobalt species) but increas ed their concentration.