Transition aluminasa, widely used as catalyst supports, play a key role in numerous refining processes.
Today, the need to develop new and more efficient catalysts demands, among other things, better understanding and control of all the individual steps involved in the manufacture of this alumina.
The precipitation of aluminum salts is a process for the synthesis of boehmite, the precursor of alumina. The conditions of this synthesis have a direct influence on the textural properties, modifying the arrangement of the elementary particles of boehmite. However, the correlation between this particle arrangement and the final textural properties of the alumina still needs to be elucidated.
To make progress in this area, we need to know how to characterize the suspensions on different scales (from particle to agglomerate) and their evolution during synthesis.
Studies have therefore been carried out in collaboration with INP-ENSIACET*, on the SWING beamline of the synchrotron SOLEIL in order to monitor by in situ SAXSbmeasurements, the aggregation and agglomeration processes of boehmite crystallites, during synthesis1.
In particular, these experiments have allowed to monitor the growth of the aggregates over time during the reagents addition. A correlation between supersaturationc at each time of the synthesis and aggregation mechanisms has thus been established: a high level of supersaturation generates very compact aggregates, whereas a low level of supersaturation leads to larger and more bulky, open structures.
Thanks to the possibility that it offers to follow continuously and at different scales the processes involved in a synthesis of materials, the SAXS technique, coupled with synchrotron radiation, provides an invaluable contribution to the development of new catalyst supports.
* Institut national polytechnique - École nationale supérieure des ingénieurs en arts chimiques et technologiques
a- Aluminas produced by the dehydration of aluminum oxyhydroxide or trihydroxide
b- Small-Angle X-Ray Scattering
c- Balance between aluminum salts and boehmite
(1) S. Kirchner, S. Teychené, S. Humbert, M. Boualleg, A. Dandeu, C. Frances, B. Biscans, A. Thureau.
Research pending publication.