Soutenance de Mathilde Auxois
| When |
Nov 29, 2024
from 02:00 to 04:00 |
|---|---|
| Contact Name | Mathilde Auxois |
| Attendees |
Mathilde Auxois |
| Add event to calendar |
vCal
iCal
|
Controlling the mechanical and textural properties of heterogeneous catalyst supports is essential for the design of innovative and efficient catalytic materials. In particular, the porous microstructure of the support strongly affects mass transport and mechanical strength. Industrially, alumina supports are manufactured using a knead-extrusion process, which aims to go from an alumina precursor powder (boehmite) to micrometric objects (the final size of the support). This process also enables the mechanical and textural properties of the substrate to be optimized by adjusting the operating conditions for each of the unit operations.
The aim of this thesis is to characterize the influence of mixing on the properties of boehmite pastes. In particular, the effects of mixing speed and duration, as well as paste composition, are quantified on the mechanical and textural properties of boehmite pastes. This experimental study, carried out on a pilot mixer, identified two parameters controlling the properties analyzed: paste pH and cumulative deformation, equivalent to the number of revolutions applied during kneading.
Then, a discrete-element model of boehmite pastes was developed to represent their microstructure (difficult to characterize experimentally) and simulate their mechanical behavior. In this model, pastes are represented as stacks of polydisperse hard spheres, and mechanical properties depend on numerical elastic and viscous parameters. The latter, like the size of the spheres, have been iteratively adjusted to reproduce experimental characterizations as closely as possible.
Keywords:Boehmite paste, kneading, porosimetry, rheometry, nano-indentation, discrete-element model