Rationalization of planetary ball milling process of boehmite γ-AlOOH: Towards operating conditions dependent transition alumina phase diagram

Abstract

To obtain catalytic porous supports with original properties, including alumina crystallographic phase, textural and acidity properties, the mecanosynthesis was investigated using the planetary ball milling process on commercial boehmite. Different combinations of milling parameters were explored to study the alumina phase transition. To rationalize all operating parameters, the energy transferred from the balls was estimated using a collision model. In the present work, boehmite transforms to χ-Al2O3, and then to α-Al2O3. All the tuned parameters can be condensed into only two independent variables that drive the alumina phase transition: the shock energy and the number of shocks. As a result, an alumina phase diagram has been established, highlighting the stability zones of boehmite, χ-Al2O3, and α-Al2O3. Additionally, the water vapor pressure induced by the dehydration of boehmite was also a key parameter to follow during milling. It could lead to boehmite reformation or the formation of tohdite and κ`-Al2O3 polymorphs.