Peptization of boehmites with different peptization index: An electron microscopy and synchrotron small-angle X-ray scattering study

[Display omitted] Boehmite AlOOH is used as a precursor for the preparation of mesoporous gamma-alumina, which is of well-known interest for use as a catalyst support in petroleum refinery. The fabrication of the shaped supports is usually decomposed in several steps: synthesis of boehmite, preparation of a paste by kneading, extrusion of the paste and finally calcination to obtain the alumina phase. Mesoporous alumina is a complex hierarchical porous network, whose growth is influenced by each step of the process, and needs to be clearly understood to optimize the catalytic performances. This paper is focused on the peptization of boehmite, an important step in the fabrication which corresponds to the beginning of the kneading. Peptization is carried out in liquid phase, from two boehmites batches with different abilities to be peptized (peptization index) and with different acid/aluminum ratios. The as-obtained suspensions are characterized by coupling electron microscopy and small-angle X-ray scattering, which bring an accurate description of the samples at their different levels of structural organization. A multi-scale mechanism of peptization is then proposed. Finally, we will discuss the study of the measure of boehmites peptization index, and confirms the textural features which are relevant for the behavior of a boehmite in an acid medium.