Isomorphic substitution of Mg²⁺ by Al³⁺ on MgO: Effects on basicity, textural properties and microstructure

The influence of aluminum atoms on the surface and structural properties of distinct mixed oxides MgAl-x (x=Al/(Al+Mg)= 0, 0.20, 0.25, 0.33 and 1.0) was studied. Hammet titration results showed that the isomorphic substitution of Mg by Al atoms induces a basicity character decrease. Theoretical DFT studies of MgAl-x oxides basicity through the oxygen Milliken charges showed a similar trend to that observed experimentally. The effect in the textural properties as a function of the Al content was observed reflected directly in the surface area and pore size distributions. Noteworthy was to observed the morphological modification on the mixed oxides with the Al content, passing from nanorods in pure MgO to hexagonal platelets in the binary oxides.

Keywords: DFT studies, Magnesia-Alumina, acid-base oxides, Isomorphic substitution, nanostructures.