?-alumina is a widely used support in catalysis, particularly in catalytic reforming where naphtha is converted to higher octane gasoline and hydrogen. In this  application, a ?-alumina is slightly chlorinated and plays the dual role of an acid function and a support for a highly dispersed promoted platinum phase. It is thus important to master the surface state of ?-alumina.The successive steps of the ?-alumina preparation were carefully controlled  to obtain a shaped catalyst that resembled industrial supports. The preparation includes the boehmite synthesis, the kneading/extrusion process and further thermal treatments to adjust textural properties. The goal of the present work is to determine which preparation steps govern the final ?-alumina surface state.Two boehmites issued from different synthesis methods were provided by Sasol. TEM and XRD show that the two boehmites have different morphologies. Their experimental IR(OH) signatures and the assignments of their individual bands (Digne et al., J.Catal., 226 (2004) 54) lead to similar conclusions. Figure1 compares the IR(OH) spectra obtained after either direct calcination of boehmite under air at 500�C or the complete preparation. Spectra presented in the lower half allows us to conclude that the alumina nanoparticle morphology has a great impact on the IR(OH) signature. Furthermore, Figure1 illustrates that the complete preparation modifies the ?-alumina surface state and that this influence depends on the initial morphology.

?-Alumina surface state control: Role of the nanoparticle morphology and the preparation steps

248th National Meeting (2014)

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