Active sulfated alumina catalysts obtained by hydrothermal treatment

The structural and surface properties of sulfated γ-Al2O3 prepared by hydrothermally aging precipitates obtained from aluminum sulfate and ammonia have been studied. The Lewis sites are formed on coordinately unsaturated fourfold alumina. No pentacoordinated aluminum has been found, probably as a consequence of the aging process. Residual sulfate is distributed among several species characterized by their desorption temperatures. Brönsted sites of high strength are probably located on sulfate species desorbing between 900 and 1000 °C. They may have the following schematic structure (O)2S(OH)(OAl). The decomposition of 4-methylpentan-2-ol shows clear differences according to the types of acidity present on the surface. The sulfated aluminas have favorable textural properties: pore size ≅ 50 nm and specific surface area ≅ 200 m2/g stable up to more than 700 °C.