Aluminum-doped mesoporous zirconia obtained from anionic surfactants

Mesoporous sulfated and oxophosphated zirconia obtained at low pH from dodecyl sulfate and phosphate, respectively, and from zirconium isopropoxide were doped with aluminum. Aluminum is produced by the simultaneous hydrolysis of aluminum alkoxide.In sulfated zirconia, aluminum forms a coating layer of amorphous alumina, but it does not seem to be introduced into the zirconia lattice. On the other hand, Al enters the lattice of oxophosphate, in addition to the formation of the coating layer. A maximum ratio of Al/Zr≈0.04 can be reached in the lattice. The introduction of aluminum into the lattice prevents the crystallization of the oxophosphate at 900°C, and helps to preserve the surface area and porosity of the sulfated zirconia above 500°C. The difference in morphology of the aluminated and phosphated zirconia and that of the nonaluminated corresponding samples parallels the observations made on porosity.