Co, Ni, Cu aluminates supported on mullite precursors via a solid state reaction

Finely dispersed Me-aluminates (Me=Ni, Co, Cu), stable up to 1000–1100°C, are obtained by diffusion and reaction with mullite precursors. The Me-aluminates are ‘reaction supported’, indeed these phases are synthesized in form of finely dispersed cristalline region in a supporting inert material, this latter providing high surface area together with thermal and mechanical stability. Two different preparative routes are exploited, the reactivity of Co, Ni is higher with route A, in which these metals diffuse and react with pre-formed γ-Al2O3 nanoparticles to form the corresponding aluminates. Cu reacts in different way, promoting the formation of mullite, without being incorporated into its structure. For this reason the preparative route which employs impregnation of 400°C mullite amorphous precursor (route B) yields complete reaction of CuO with alumina to form Cu-aluminate, dispersed on a mullite substrate at the final temperature of 980°C. This material shows remarkable catalytic activity in CH4 oxidation.