Synthesis of high surface area CoAl2O4 and NiAl2O4 spinels by an alkoxide route

The mixed metal oxides CoAl₂O₄ and NiAl₂O₄ were prepared in a high surface area form by using a sol-gel method which involves hydrolysis of cobalt-aluminium and nickel-aluminium isopropoxides. The resulting gels were calcined at 673 K to yield the corresponding spinel-type metal oxides. Powder X-ray diffraction was used to confirm spinel formation. Nitrogen adsorption-desorption measurements have shown the materials obtained to be highly porous. The BET surface area was found to be 240 m²g⁻¹ for CoAl₂O₄ and 255 m²g⁻¹ for NiAl₂O₄. Both materials showed a unimodal distribution of pore radii, where the most frequent pore radius is 5 nm for cobalt aluminate and 3 nm for nickel aluminate.