Effect of calcination temperature and chemical composition on the surface properties of Co3 O4 supported on gamma-Al2O3

ABSTRACT

A series of Co[3]O[4] supported on gamma-AL[2]O[3] was prepared by impregnating a finely powdered poorly crystalline gamma-alumina samples with cobalt nitrate solution containing different proportions of Co[No3][2] using a pore-filling method. The obtained solids were dried at 100C then roasted at temperatures between 450 and 750C. The cobalt content was varied between 10.5 to 37.1 Wt.% Co[3] O[4]. The surface charateristics namely, specific surface area, total pore volume and mean pore radius of various supported catalysts were determined from N[2] adsorption isotherms measured at 77CK. The results obtained revealed that both specific surface area and total pore volume of the employed alumina support display an important decrease by loading with cobalt oxide. The SBET of certain of the investigated solids decrease progressively by increasing the roasting temperature from 450 to 750C. The SBET of all samples decreases at 750C. This decrease becomes more pronounced on increasing the Co[3]O[4] content from 0.05 to 0.1 mole/mole AL[2]O[3] and less pronounced thereafter. The surface area is largely stabilized in the samples with 0.25 Co[3] O[4] alumina