Title :

Chemical Weathering of Alumina in Aqueous Suspension at Ambient Pressure: A Mechanistic Study

Author(s) :

Abi Aad, Jane [Auteur]
Casale, Sandra [Auteur]
Michau, Mathieu [Auteur]
Courty, Philippe [Auteur]
Diehl, Fabrice [Auteur]
Marceau, Eric [Auteur]
Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181
Unité de Catalyse et Chimie du Solide - UMR 8181 [UCCS]
Carrier, Xavier [Auteur]

Journal title :

ChemCatChem

Volume number :

9

Pages :

2186-2194

Publication date :

2017-02-27

HAL domain(s) :

Chimie/Catalyse

English abstract : [en]

Transition aluminas rank among the main supports used for heterogeneous catalysis. Their stability in the aqueous phase is a key issue for catalytic processes, as their hydration can be strongly detrimental to their ...
Show more >Transition aluminas rank among the main supports used for heterogeneous catalysis. Their stability in the aqueous phase is a key issue for catalytic processes, as their hydration can be strongly detrimental to their physicochemical and mechanical properties. As a consequence, the design of more stable alumina-based supports relies on a better understanding of the mechanisms leading to their chemical and physical degradation. It is shown here that if suspended in water at atmospheric pressure and at temperatures up to 70 °C, all transition aluminas (from γ to θ-Al2O3) transform into Al(OH)3 polymorphs (bayerite, gibbsite, and nordstrandite), although to different extents. A quantitative study of the aluminum concentration in solution and of the amount of hydroxides demonstrates that Al2O3 hydration occurs through a two-step dissolution/heterogeneous precipitation process, with nucleation of Al(OH)3 on the surface of the alumina grains followed by particle growth. The grains become more fragile because of chemical weathering; the ensuing mechanical degradation by attrition, in turn, brings the weathering process to completion. The nature of the main hydroxide polymorph is a function of aluminum concentration and ageing time: first the kinetic product, bayerite, then nordstrandite and eventually gibbsite, the most thermodynamically stable hydroxide. Increasing crystallinity and decreasing specific surface area of alumina leads to a reduced amount in hydroxide formation.Show less >

Language :

Anglais

Audience :

Internationale

Popular science :

Non

Administrative institution(s) :

ENSCL
CNRS
Centrale Lille
Univ. Artois
Université de Lille

Collections :

• Unité de Catalyse et Chimie du Solide (UCCS) - UMR 8181

Research team(s) :

Matériaux pour la catalyse (MATCAT)

Submission date :

2019-09-25T14:06:31Z